Textbook of

FOOD SCIENCE
AN D
TECHNOLOGY
VIJAYA KHADER
 Digitized by the Internet Archive
in 2018

https://archive.org/details/textbookoffoodscOOOOkhad
Textbook of
Food Science and
Technology
Textbook of

Food Science and

Technology

VIJAYA KHADER
Director
Centre of Advanced Studies in Foods and Nutrition
Post-graduate and Research Centre, College of Home Science
Acharya N.G. Ranga Agriculture University
Rajendranagar, Hyderabad 500 030, Andhra Pradesh

Published by
Directorate of Knowledge Management in Agriculture
Indian Council of Agricultural Research
Krishi Anusandhan Bhavan-I, Pusa
New Delhi
 Printed September 2001
First Reprint June 2013
Second Reprint May 2016

Project Director (DKMA) Dr Rameshwar Singh

lncharge (English Editorial Unit) Dr Aruna T Kumar

Chief Production Officer Dr V K Bharti

Assistant Chief Technical Officer Kul Bhushan Gupta

All Rights Reserved

© 2016, Indian Council of Agricultural Research, New Delhi

ISBN : 978-81-7164-133-8

Price : ? 500

Published by Dr Rameshwar Singh, Project Director, Directorate of Knowledge

Management in Agriculture, Indian Council of Agricultural Research, Krishi
Anusandhan Bhavan-I, Pusa, New Delhi 110 012 and printed at M/s Chandu Press,
D-97, Shakarpur, Delhi 110 092.
 Foreword

The moment food is harvested, gathered and caught, its progressive

deterioration starts. And to preserve or store food, food processing, an
important science, needs to be given due impetus in the present scenario.
The status of food-processing sector varies in different countries
depending on the variety of factors, while the basic food is an essential
inevitable input for life sustenance. The economic dimension of the food¬
processing industry is influenced by the extent of the processed foods find
their way in the day-to-day menu of the family. The use of additives in foods
is not new, but their excessive use in recent years has raised issues that
place certain responsibility upon the food technologists and the government.
The present-day market has a tremendous array of foods which were
unheard of 10 or 15 years ago. But the quality and characteristics of many
of the convenience foods compare very favourably with home-prepared foods.
Street foods have also an enormous impact on the urban food supply,
economically as well as socially and nutritionally. An excellent measure of
technological advancement of a society is the extent to which the refrigration
and frozen food processing, transportation, storage and merchandizing
facilities are developed.
According to one school of thought, Food Science and Food Technology
is not treated as two separate subjects but as broad divisions of what, in
truth, is a continuous spectrum. Undoubtedly, the relationship between
the Food Science and Food Technology is subtle and complex.
Food Science today brings together such specialists as physicists,
mathematicians and rheologists to study extensibility and extrusion
properties of bread dough; the microbiologists, nutritionists and toxicologists
to investigate safety of a processed food; microwave engineer, packaging
engineer, and statistician to define a quality controlled high speed unit
process; and political scientists to decide the feasibility of a new source of
food for narrowing gap between world food production and increasing
population.
Food Science and Technology will offer avenues for the integration of
different kinds of knowledge base for the betterment of society. Besides,
this will offers great challenges to researchers, teachers and writers of the
texts.
Considering long-felt need for a textbook on Food Science and
Technology, the help of Dr (Mrs) Vijaya Khader, Director, Centre of Advanced
 FOREWORD

Studies in Foods and Nutrition, Achaiya N.G. Ranga Agricultural University,

Hyderabad, was sought. I congragulate Dr (Mrs) Vijaya Khader for writing
‘Textbook of Food Science and Technology’, covering very relevant and various
aspects such as physico-chemical properties of foods, food enzymes, food
additives, water activity, evaluation of food, foods of plant and animal origin,
novel foods, baked products, packaging, food laws and quality control.
It is hoped that this textbook will be of immense value to all who are
concerned with food. In particular, it will provide wealth of information and
excellent reference material to post-graduate students of Food and Nutrition
and Food Science, Home Economists, catering and nutrition schools, colleges
of education, technical colleges and universities and students of medicine
and nursing.

(Dr M. V. Rao)
Former Vice-Chancellor
Acharya N.G. Ranga Agricultural University
Hyderabad, Andhra Pradesh
 Preface

Food has been a basic part of our existence. Through the centuries we have
acquired a wealth of information about the use of food as a part of our
community, social, national and religious life. It has been used as an
expression of love, friendship and social acceptance.
The desire to write a Textbook of Food Science and Technology had
inculcated in me while I was teaching Food Chemistry, Food Science and
Proteinous Foods; as there was no good textbook available which combined
at a fairly elementary level, a discussion of chemical nature of food with
description of what happens to food when it is processed.
I was fully aware that to cover knowledge so broad as is encompassed
by the terms Food Science and Technology, even in elementary fashion, in a
single spine is undoubtedly a difficult task. But the book was initiated with
the hope that it will help to fill several needs. The scientific study of food is
one of the man’s most important endeavours. And food processing and
handling is the largest of all man’s industries as the complexity of foods,
their vulnerability to spoilage, their role as a disease carrier, the different
sources of foods, the availability, nutritional adequacy and the wholesomeness
of foods are quite vaired.
The literature on food science and technology is extensive in its detailed
treatment of specific commodities, unit operations and control methods.
However, an attempt has been made to provide as much knowledge as
possible in a nutshell in the following 7 parts covering all food groups. It is
very important for all those who deal with food to understand scientific
basis of modern methods of food processing.
The book deals successively with the main food commodities such as
cereals, millets, legumes, nuts and oilseeds, meat, fish, eggs, milk and milk
products, vegetables and fruits and the principal processes of food technology
applied to each. The purpose of the work is to outline the way in which the
knowledge of the chemical composition of different food commodities or of
biological characteristics of certain types of micro-organisms can be applied
to achieve results.
The key methods for food processing and their principles, modes of
action, and assets or limitations are presented in a comprehensive way in
this publication. Special emphasis has been given to preservation techniques.
 PREFACE

Food chemistry is reviewed to the degree required for understanding

fundamental changes, and for techniques in handling and processing. The
diagrams are in most cases used to elucidate principles rather than
experimental findings.
This publication will serve as a useful reference book to under-graduate
and post-graduate students of Food and Nutrition and Food Science; to
teachers of these disciplines; to Home economists and nutritionists. This
will also be of interest to industrialists, researchers, professionals and all
others in fields related to safety and wholesomeness of foods, and those
concerned with how Food Science and Technology will be instrumental in
human survival.

Vijaya Khader
 Acknowledgements

The author expresses her sincere and deep gratitude to Dr M.V. Rao, former
Vice-Chancellor, Acharya N.G. Ranga Agricultural University, Hyderabad,
for the continuous encouragement given by him in the preparation of this
textbook. I owe special thanks to Acharya N.G. Ranga Agricultural University
for permitting me to write the textbook.
The author wishes to thank the Indian Council of Agricultural Research
(ICAR), New Delhi, for providing timely financial assistance for preparing
the manuscript and printing of the book.
A note of special thanks is to Ms K. Radhika Rani and Ms M. Aruna for
their untiring and invaluable assistance during collection of references.
I owe much to my husband Mr Abdul Khader for his support and valuable
help at every stage of writing this textbook.
I acknowledge the professional excellence and pains taken by Mr K.P.
Sagar, Sagar Computers.

Vijaya Khader
r
.

.
 Contents

Foreword
Preface
Acknowledgements

Part I Introduction to food science

1. Classification of foods and science of processing 1
2. Physico-chemical properties 6
3. Hydrogen-ion concentration 12
4. Food enzymes 15
5. Colloidal system 19
6. Food additives 30

Part II Food safety, quality and evaluation

7. Evaluation of food 39
8. Food adulteration, food standards and labelling 46
9. Microbes in foods 73
10. Food spoilage 86

Part HI Plant food products and processing techniques

11. Cereals and millets 97
12. Legumes 138
13. Nuts and oilseeds 152
14. Fats and oils 167
15. Fruits and vegetables 178
16. Beverages 219
17. Condiments and spices 241
18. Miscellaneous foods—sugar, jaggery and cocoa butter 252

Part IV Animal food products and processing techniques

19. Milk and milk products 271
20. Eggs 294
21. Meat, poultry and fish 305
 CONTENTS

Part V Baking process and products

22. Baking, ingredients, leavening agents and ovens 329
23. Biscuits, breads and rolls 349
24. Cakes, cookies and pastries 356
25. Microwave cooking 368

Part VI Novel food production and processing

26. Mushrooms 381
27. Blue green algae (Spirulina) 385
28. Leaf protein concentrates (LPC) 392
29. Protein from petroleum yeast 395
30. By-products of oilseeds 401
31. Food analogue 406
32. Fermented soya products 410
33. Irradiated and radiated foods 418

Part VII Food packaging

34. Packaging material 429
35. Packages of radiation stabilized foods 437
36. Packages of dehydrated products 444

Index 451
Part I

Introduction to
Food Science
 i

■V
0 lU • -
 Classification of foods
and science of processing i.
I ndia has great degree of social, economic and cultural diversity. The socio¬
economic status of different sections of the population, food habits of the
people in different states, traditional methods and practices of processing
and preservation of food material vary greatly in different geographic areas.
Food is intimately woven into the physical, economic, psychological and
social life of man. It is a part of his culture and is filled with many different
meanings and symbolisms for all individuals at various ages and stages of
their maturity. Scientific study of food is one of man’s most important en¬
deavours, mainly because food is his primary need. Food processing and its
preservation is now carried out primarily in large factories or in the small-
scale establishments. The chemical complexity of foods, their vulnerability
to spoilage, their role as a disease vector, and the varied sources of foods,
the availability and the wholesomeness of foods are also quite varied (Gaman
and Sherrington, 1989).
Early man used to get food through hunting animals. Man’s hunger
and his food harvest is not usually in harmony, throughout the year, in any
one location.
Primitive humans gathered food as early as one million years ago. They
fed themselves by harvesting wild fruits, vegetables and catching small ani¬
mals, insects and fish. From earliest human history to the present, food
gathering and processing have become more diversified and complex. The
problem of the quantity and quality of the food supply to the world is of the
great concern to all nations.
Food Science has been defined by Margaret (1968) as the application of
the physical, biological and behavioural sciences to the processing and
marketing of foods. Although the main emphasis in food science is on tech¬
nology, the nutritional aspects should get the due attention as food is eaten
primarily to satisfy the needs of the body for nutrients.
Technology can be defined as the science dealing with the knowledge of
doing things efficiently and effectively. Food science and technology maintains
special relationships with several basic disciplines as well as with a number
of applied specializations.
Food science and food technology are not two separate subjects but
merely broad divisions of continuous spectrum. The relationship of food
science and food technology are subtle and complex. Food science helps us
understand the theoiy, e.g. what methods can best be used to store and

1
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

preserve food to maintain quality and prevent spoilage. Food technology

demonstrates how the food is stored, preserved, processed and transported,
and has been responsible for development of new techniques for processing
and preserving food on a commercial scale and for packaging it in such a
way that it can be sold conveniently.
Food science and technology is relatively a new field. Of late, it has
began to achieve a degree of technical maturity in its development, nationally
and internationally. It is a viable, important and necessary field of study for
those who wish to pursue technical careers in food processing and preser¬
vation. It is multidisciplinary and encompasses many subjects. Food science
deals with the study of facts of the physical, chemical and biological sciences,
as they influence the processing and preservation of food (Fig. 1).

Fig. 1. Food science and technology in the universe of science and technology (Source. Stewart and
Amerine, 1982)

1
2
 CLASSIFICATION OF FOODS AND SCIENCE OF PROCESSING

Food technology deals with engineering and other scientific and technical
problems involved in transforming edible raw materials and other ingredients
into safe, nutritious, and appetizing food products (Desrosier, 1977). Food
science is concerned with the basic scientific facts about food, whereas food
technology is concerned with the processing of raw materials into foods that
meet human needs and wants. Indian agriculture has undergone a sea
change during the past half a century. Starting with the campaign for ‘grow
more foods’ in the forties, India reached ‘self-sufficiency’ during the eighties.
Thanks to the ‘Green Revolution’ which swept the country. Advancing knowl¬
edge of food science and engineering developments have made possible the
large-scale processing and preserving of food. Accordingly, food science and
technology has developed over the past four or five decades into a large
scientifically well-ground, and technically sophisticated speciality.
It must be remembered that food is eaten primarily to satisfy the hunger
and needs of the body for nutrients. This fact makes it clear that food scien¬
tists should have a basic understanding of human nutrition if they are to
carry out properly the job of converting raw agricultural, animal and sea
products into nutritious as well as acceptable processed foods.
Foods may be broadly classified as cereals, pulses, nuts and oilseeds,
vegetables, fruits, milk and milk products and fleshy foods. These foods
contain substances known as nutrients which perform various functions in
the body.
Foods for body building: Foods rich in protein, mineral, vitamin and water.
Foods for energy: Foods rich in carbohydrates, fats and protein.
Foods for regulating body process: Foods rich in minerals, vitamins, water
and fiber.
Proteins form the major cellular structural elements are biochemical
catalysts and are important regulators of gene expression. The above nutri¬
ents are present in almost all foods in varying proportions. As far as the
science and technology is concerned the foods are broadly classified as:
(i) plant foods such as cereals and millets, legumes, nuts and oilseeds, spices
and condiments and miscellaneous foods and (z'i) animal foods such as milk,
meat, fish, egg and poultry.

FOOD PREPARATION

Neolithic food preparation was primarily a home industry. A hypothetical

chronology for development of cooking techniques is given in Fig. 2. All of
these originated in the home kitchen. Among the new food preparation tech¬
niques developed were sieving, salting, seasoning, pressing, alcoholic
fermentation, acetification (vinegar formation), and bread making. It is
interesting to note that some of these are still used in the home, whereas
others are employed by commercial food processors.
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Radiant heat
(Roasting, broiling, grilling)

Stick Grid iron

Conduction
of heat
Cooking on top of
■W bars and grills

Indirect Direct

j
Immersion of pre¬ Use of steam and moist
Cooking in ashes or
embers

heated stones in heat (steaming)

infusions
Cooking on top of
heated stones

Cooking in pottery or metal Cooking in preheated vessel

vessels in hot liquid (primitive baking)
(water, 87.8-100°C) (boiling)
(kitchen fires)

Long, slow cooking in little liquid Cooking in enclosed heated

in tightly covered vessel in oven space (baking)
(stewing)

Haybox-cooking Braising Baking furnace

Pressure-cooking (high
temperature under pressure
of own steam)

Fig. 2. Evolution of cooking techniques

 CLASSIFICATION OF FOODS AND SCIENCE OF PROCESSING

REFERENCES

Desrosier, N.W. 1977. Elements of Food Technology. AVI Publishing Company, I.N.C., West
Port, Connecticut.
Gaman, P.M. and Sherrington, K.B. 1989. The Science of Food: an Introduction to Food Science,
Nutrition and Microbiology. Edn 2. Maxwell Macmillan International editions (Reprint).
Margaret, Me Williams. 1968. Food Fundamentals. John Wiley & Sons Inc., New York, London,
Sydney.
Stewart, G.F. and Amerine, M.A. 1982. Introduction to Food Science and Technology. Edn 2.
Academic Press, New York, London.

LEARNER’S EXERCISE

1. Enumerate the evaluation of cooking techniques.

2. ‘Food science and technology are not two separate subjects, but merely broad division of
continuous spectrum—Enumerate.
3. Explain in brief the need and importance of food processing.
4. Mention the objectives in the study of foods and explain each objective with suitable
examples.
5. What are the different methods of cooking foods? Explain how each method affects the
quality of foods.
2. Physico-chemical
properties

F oods are generally complex materials. The properties of their compo¬

nents determine the sensory characteristics or quality of food. Food
components are in the form of solids, in solution, or in the form of colloidal
sols or emulsions. These undergo various physical and chemical changes
when exposed to various conditions and treatments. A knowledge of the
scientific principles of these changes is necessary to understand and con¬
trol the changes occurring in foods during handling. The scientific princi¬
ples governing the physical and chemical properties of foods are discussed
in this chapter.

PHYSICAL PROPERTIES OF SOLUTIONS

A solution is a homogeneous mixture of two or more substances dissolved in

a medium in which the molecules of dissolved substances are uniformly
distributed in the solution. The amount of solute that can be dissolved in a
given amount of solvent at a given temperature is expressed as solubility.
Solubility varies with temperature. The extent to which a solute can be
dissolved in a solvent depends on the attractive forces between the solute
and solvent molecules, and the solvation of the solute, i.e. the attachment of
molecules of the solvent to solute molecules of ions, by electrical attraction
or chemical bonding. The water molecule is highly polar and so water is an
excellent solvent for ionic substances. The solvation that takes place in this
case is known as hydration.
If both solvent and solute consist of polar molecules, there is also strong
electrical attraction between the two dipoles. This results in solvation and
good solubility. The solvation of molecules is often increased by formation of
hydrogen bonds. Therefore, polar solvents like water are good solvents for
polar molecules and for ionic substances (Shakunthala and Shada-
ksharaswamy, 1995).
The concentration of a solution is the amount of the solute dissolved in
a specific amount of solvent or solution. When the concentration reaches a
point when no more solute can dissolve in a solvent at a particular tempera¬
ture, the solution obtained is said to be saturated. If a saturated solution of
a solid is prepared at or near the boiling point of the solvent, on cooling, the
solid crystallizes out.

6
 PHYSICO-CHEMICAL PROPERTIES

When a saturated solution is carefully cooled, crystals may not sepa¬

rate out. Such a solution holds more solute than could normally be present
at the same temperature. This solution is called supersaturated. The
supersaturated solutions are unstable and become more unstable with the
increase in degree of supersaturation. Crystals do form ultimately when the
solution becomes fairly cool. This phenomenon is of importance in sugar
cookery.
Several properties of solutions are particularly important in food prepa¬
ration. Amongst these are the colligative properties, such as vapour pressure,
boiling point, freezing point and osmotic pressure (Belle, 1955).

Vapour pressure
The intermolecular forces in a liquid prevent escape of most molecules
from the surface. However, due to molecular collisions some molecules have
sufficient kinetic energy to escape from the liquid. This causes the evapora¬
tion of the molecules into the gaseous state. Any liquid therefore has above
its surface a certain amount of pressure in the form of vapour. Vapour
molecules move in all directions. Some of vapour molecules that strike the
surface of the liquid get condensed. When the rate of evaporation and con¬
densation are equal, an equilibrium is established. The pressure exerted by
vapour above the liquid when equilibrium exists is vapour pressure. The
vapour pressure is temperature dependent.
When a solid is dissolved in a volatile solvent the vapour pressure of the
solution is less than the vapour pressure of the pure solvent because of the
presence of solute molecules. In a solution, the number of solvent mol¬
ecules at the surface is reduced and therefore the rate of evaporation is less
than for the solvent. The extent of lowering is proportional to the number of
molecules of solvent compared with the total number of solvent plus solute
molecules. For example, when equal quantities of sucrose and sodium chlo¬
ride are dissolved in a known amount of water at constant temperature, the
lowering of the vapour pressure of water by sodium chloride is twice com¬
pared with that of sucrose, because sodium chloride contains 2-time more
number of ions than of sucrose molecules in the solution. Properties of
solution which depend on relative number of molecules present and not on
their chemical nature are known as colligative properties. These properties
hold good if the solution is dilute.

Boiling point
A liquid boils when its vapour pressure is equal to the external pres¬
sure. The boiling point is thus constant for any external pressure. The nor¬
mal boiling point (BP) refers to an external pressure which is equal to the
atmospheric pressure (760 mm Hg), which for water is 100°C. With an in¬
crease in pressure the boiling point increases, e.g. the boiling point of water
at 770 mm is 100.37°C. In a pressure cooker, a greater external pressure
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

must be overcome and so the boiling point is elevated. At 103 kg/kolopascal,

water boils at 121°C. Conversely, at a reduced atmospheric pressure, as in
high altitudes, the boiling point is lowered. For each 290 m increase in
altitude above sea-level, the boiling point of water is lowered by 1°C.
As already stated, dissolved substances reduce the vapour pressure of
a solvent resulting in a higher temperature being required for a solvent to
boil, i.e. dissolved substances elevate the boiling point. One mole of a non¬
volatile nonionizing solute raises the boiling point of a litre of water by 0.52°C.
Ionic materials elevate the boiling point to a much higher extent than
nonionizing substances. For example, sodium chloride forms two ions and
calcium chloride three ions in solution and, if they undergo complete ioniza¬
tion, one mole of them could raise the boiling point of a litre of water by
1.04° and 1.56°C respectively.
A knowledge of elevation in boiling point is useful in the processing of
foods, such as jams, jellies, syrups, confectionery, etc., which are liquids at
higher temperatures, to determine the concentration of sugars, and the
properties the materials will have on cooling.

Freezing point
The freezing point of a material is the temperature at which it changes
from a liquid to a solid. A liquid freezes when its vapour pressure is equal to
the vapour pressure of its solid. The freezing point of water is 0°C.
The freezing point of solvent is depressed when a solute dissolves in it.
A mole of nonionizing solute in a litre of water depresses its freezing point by
1.80°C. A mole of sodium chloride or calcium chloride could depress it by
3.72°C and 5.58°C for reasons given under boiling point. The practical im¬
portance of this is that a mixture of ice, water and salt gives freezing mix¬
tures. Ice and water alone are in equilibrium at 0°C, but if salt is added
some ice will melt to reduce the temperature to the new equilibrium posi¬
tion. Ice, salt and saturated salt solution (29 parts of salt to 71 parts of ice)
gives a freezing mixture with a temperature of - 21°C and therefore is used
in making home-made ice-cream.
The freezing point of milk is 0.53°C which is determined by presence of
its soluble constituents, lactose and salts. Since these soluble components
vary in milk only slightly, the freezing point remains almost constant. This
makes it possible to determine any dilution of milk. Addition of 1% by vol¬
ume of water to milk rises the freezing point by approximately 0.0055°C.
Freezing is a means of preservation of food.

Osmotic pressure
Osmosis is the flow of solvent into a solution, or from a more dilute
solution to a more concentrated one, when the two liquids are separated
from each other by a semi-permeable membrane. The membrane contains
minute pores through which the solvent molecules can pass. The phenom-

8
 PHYSICO-CHEMICAL PROPERTIES

enon of osmosis causes a change in the relative volume of the two liquids
separated by the semi-permeable membrane. The volume of the solution
that becomes more dilute increases. Osmotic pressure is the pressure re¬
quired to prevent that increase in volume or osmosis.
Osmosis occurs in food. In fruit cooking, when the fruits are cooked in
water, the fruit increases in size as the water flows into the fruit tissues
where the sugar concentration is higher. If, on the other hand, fruits are
cooked in syrups having a sugar concentration higher than that of the fruit,
the fruit gets shrivelled, because of passage of water through the fruit skin
into the syrup. Osmosis is also a very important process in living organisms.
Viscosity
Viscosity is associated with fluid flow. It is the internal friction which
tends to bring to rest portions of the fluids moving relative to one another.
This is measured in relation to some standard viscosity, generally of water
at 25°C. A number of factors affect the viscosity of a fluid; for instance, large
changes take place due to temperature. In the case of a colloidal system,
factors in addition to temperature, such as the particle size distribution,
nature of the particle surface, particle shape and volume of dispersed phase,
etc. affect the viscosity of the fluid. Viscosity is expressed as centipoises
(Toledo, 1980). Instruments used for evaluating the flow characteristics of
fluids are called viscometers.
Viscosity determination is useful in the study of consistency of foods.
Viscometric measurements are made in the food industry for study of food
structure. Viscosity affects heat transfer during pasteurization in the prepa¬
ration of certain food materials, such as fruit juices. Hence the viscosity and
the rate of change of viscosity with change in temperature, are the factors of
importance in food industry (Griswold, 1962).
Surface and interfacial tensions
The boundary between a liquid and a gas or vapour is termed surface,
whereas that of a liquid-liquid or a solid-liquid junction interface. There is
an attractive force between molecules in a liquid. For a molecule in the body
of the liquid, these forces tend to cancel according to directions so that there
is no net force. Molecules at the surface or interface are not surrounded
completely by other molecules of the same type and the same physical state.
This results in a net attractive force for each molecule directed towards the
interior of the phase in which the molecule resides. This inward attraction
reduces number of molecules at the surface or interface and, as a result,
the surface or interfacial area is reduced to a minimum. For example, a
drop of oil in water will always tend to assume a spherical shape since the
forces cause the surface to contract to the smallest possible size. A drop of
water on a greasy surface behaves in a similar way. The forces causing a
reduction in surface or interfacial area are called as surface tension and
interfacial tension respectively.

9
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Intermodular attractions like hydrogen bonding and van-der-waal forces

(weak attractive forces between molecules) are responsible for surface and
interfacial tensions. With polar compounds like water both these forces are
important, whereas only van-der-waal forces are operative in non-polar liq¬
uids, such as triglycerides.
A number of factors affect surface tension. Increase in the temperature
of a liquid phase decreases the surface tension; the decrease with water is
greater than with triglycerides. Since water and triglycerides are the most
important food liquids, marked difference in surface tensions of these two
liquids is important in food preparations. The interfacial tension between
edible oils and water is important in creation and stability of many food
emulsions.
The presence of a solute influences the surface tension of water. With
solutions of inorganic salts and compounds with a large number of hydroxyl
groups (e.g. sucrose), surface tension increases slightly with the increase in
concentration of solute. Many organic compounds including hydrophilic col¬
loids like proteins are surface acting agents (surfactants) rapidly decrease
the surface tension. Surface active agents which have a balance of both
polar (hydrophilic) and non-polar (hydrophobic) groups are adsorbed at the
surface of a solution. This results in reduction of surface tension. Lipids,
such as phospholipids, salts of fatty acids and monoglycerides, have sur¬
face active properties.

Specific gravity
The density of a substance is defined as mass per unit volume. The
density of a substance is a characteristic property and has a definite value
at a given temperature and pressure. The density of one substance in rela¬
tion to the density of another material (e.g. water) is known as specific grav¬
ity. Therefore, specific gravity is the weight of a given substance referred to
the weight of an equal volume of water at a definite temperature (Shakunthala
and Sadaksharaswamy, 1987).
The specific gravity of food depends on their components. The specific
gravity of milk, for example, is greater than that of water as its constituents,
except fat, have specific gravities higher than that of water. The average
specific gravity of milk is 1.032 (at 15.5°C); it ranges from 1.027 to 1.035. If
the fat content of milk increases, the specific gravity decreases (up to 0.93)
and if the non-fat components increase, the specific gravity increases. The
actual specific gravity is a function of the two. Similarly, the specific gravity
of fats is the resultant specific gravity of the component triglycerides.
Considerable use of specific gravity is made in the purchase of products
like syrups, foams, jellies, milk, cream, ice-cream and alcoholic beverages.
It is also useful in the control of processing during the production of these
compounds. Specific gravity indicates the amount of air incorporated into
products (lightness of products), such as whipped cream, egg-white foam,
creamed shortening and cake batter.

10
 PHYSICO-CHEMICAL PROPERTIES

REFERENCES

Belle, L.W. 1955. Experimental Cookery from the Chemical and Physical stand point, pp. 1-33.
John Wiley & Sons, Inc., New York; Chapman & Hall Ltd, London
Grisword R.M. 1962. The Experimental Study of Foods, pp. 29-34. Indiana University, Houghton
Mifflin Co., Bostan.
Shakunthala M.N. and Shadaksharaswamy, M. 1995. Foods: Facts and Principles, pp. 130—
34. Wiley Eastern Ltd, New Delhi.
Toledo, R.T. 1980. Fundamentals of Food Process Engineering, p.163. AVI Publishing Co.,
West Port, Connecticut.

LEARNER’S EXERCISE

1. Explain in detail colligative properties: vapour pressure, boiling point, freezing point and
osmotic pressure.
2. What do you understand by surface tension and interfacial tension? Where it is used?
3. Define specific gravity and explain how it differs in foods based on their components?

11
I

3 Hydrogen-ion
■ concentration

T he term pH is the symbol for hydrogen-ion concentration which is used

to express the degree of acidity or alkalinity of a food or a given solution.
The hydrogen-ion concentration of a food is a controlling factor in regulating
many chemical and microbiological reactions. The pH is the negative loga¬
rithm to the base to the hydrogen-ion concentration. The pH or buffering
action is very important in foods (Manoranjan Kalla and Sangita Sood, 1996).
It is evident that the acidity and alkalinity of foods are of great importance
in food processing.
Some foods, e.g. fruits, contain organic acids and have an acid reaction,
whereas foods such as milk and eggs have a neutral reaction. For example
when milk is kept exposed for a long time, it curdles while being heated due
to development of acidity in milk. Similarly, when lemon juice is added to
milk, the protein (casein) present in milk precipitates along with fat. Milk
contains several salts such as potassium and sodium phosphates which are
responsible for its stability. Hence acidity and alkalinity of foods are of gen¬
eral importance in food processing (Swaminathan, 1987).
Hydrogenion concentration has to be contained within narrow limits to
co-ordinate various biological activities in an aqueous system. It is impor¬
tant for proteins to have stable, ‘native’ structure which is highly dependent
on pH. For example, the catalytic activities of enzymes are drastically al¬
tered on moderate changes in pH. Lactic acid production in muscle, an
enzymatic process, falls by 37% when H+ concentration increases from 40
nmol/litre (pH 7.4) to 85 (pH 7.1). Blood plasma pH which is fair reflection of
intracellular pH, is maintained within very narrow limits (7.35-7.45). When
blood pH goes above 7.8 tetany occurs. Conversely, excessive acidity (pH
less than 7.0) results in coma (Pattabiraman, 1994).

HYDROGEN ION

There is a small but definite tendency of hydrogen to dissociate from a water

molecule resulting in the formation of hydrogen and hydroxyl ions.
H20 <—>- H+ + OH”

, (H+) (OH”)
K = —-' = 1.80 x 10 mole (at 25°C) (H20)
(H20)
 HYDROGEN-ION CONCENTRATION

The dissociation constant indicates that the reaction lies far to the left.
Kw, the ionic product of water is very small. When (H) is more than 10"7
M, the solution is acidic and conversely, when it is less, the solution is
alkaline.
Acids are compounds that release protons and bases are proton accep¬
tors. HC1 is an acid and Cl is a conjugate base.
HCI -<—H+ + Cl-
CH3COOH ^ H + CH3COO-

Similarly, acetate anion is the conjugate base of acetic acid. In dilute

solutions, HCI for all practical purposes, is completely dissociated into H+
and Cl'. Thus, HCI is a strong acid and Cl" is a weak acid.
Acids may be defined as compounds which yield positively charged hy¬
drogen ions in solution; bases, are compounds which yield negatively charged
hydroxyl ions in solution. Strong acids, such as HCI are highly ionized at all
concentrations; they therefore have a hydrogen-ion concentration nearly
equal to the concentration of acid present. Weak acids, such as acetic acid,
exist in solution largely in the molecular or undissociated form, and have a
hydrogen-ion concentration under ordinary conditions which is small rela¬
tive to the total acid concentration. A similar distinction is made between
strong bases and weak bases. Most neutral salts are considered to be com¬
pletely ionized in solution.
When acids react with bases a double decomposition occurs which re¬
sults in the formation of a salt and water, as in the following equation.
HA H+ + A-
(Acid)
BOH -<—> OH- + B+
(Base)
H20 BA
(Water) (Salt)

Such reactions, known as neutralization reactions, go to completion

because the water formed during the reaction is itself so feebly ionized that
its formation leads to the removal of practically all of the hydrogen and
hydroxyl ions from solution. The amount of base required to neutralize a
definite volume of acid (i.e. the titratable acidity) depends entirely on the
concentration of the acid and is independent of its degree of dissociation.
This fact becomes evident upon study of the above equation. As the base is
added some of the hydrogen ions in the solution combine with the added
hydroxyl ions to form water, and are thus removed from solution. This re¬
moval of hydrogen ions disturbs the equilibrium between the undissociated
molecules of acid and its ions, and more of the acid dissociates in an at¬
tempt to restore this equilibrium. If sufficient base is added this process will
continue until all of the acid has been dissociated and neutralized. This will
be the case irrespective of whether the acid was originally highly ionized or
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

feebly ionized—whether it was a strong acid or a weak acid. On the other

hand, the hydrogen-ion concentration of an acid—the actual amount of free
hydrogen ions present in the solution at a particular time—depends not
only on the concentration of the acid but also, for weak acids, on the degree
of dissociation (Bernard, 1965).

REFERENCES

Bernard, L. 0. 1965. Hawk’s Physiological Chemistry, edn 14. McGraw-Hill Book Co., New
York, Toronto, London.
Manoranjan Kalla and Sangita Sood. 1996. Food Preservation and Process. Kalyani Publishers,
Ludhiana.
Pattabiraman, T.N. 1994. Concise Medical Biochemistry. Gajanana Book Publishers & Dis¬
tributors, Bangalore.
Swaminathan, M. 1987. Food Science Chemistry and Experimental Foods, p. 10. The Bangalore
Printing & Publishing Co. Ltd, Bangalore.

LEARNER’S EXERCISE

1. Explain the role of hydrogen-ion concentration in respect to culinary aspect.

2. What is the effect of water of various acidities and milk upon colour, texture and flavour
of a green vegetable?
3. What is the effect of colour of white vegetable on cooking in alkaline water or distilled
water?
 Food
enzymes

E nzymesare complex organic catalysts which bring biochemical reactions

in plant and animal tissue. Enzymes cause many desirable changes in
foods during processing.

AMYLASE

Amylase is the best used enzyme in industry. Bacterial liquefying a-amylase

is widely employed for liquefaction in starch processing for various pur¬
poses, mostly in conjunction with other amylases. Mould a-amylase is used
in the baking industry, due to its heat instability. Mould glucoamylase is an
important enzyme in the production of glucose and glucose syrup, and in
alcohol fermentation. Plant and bacterial P-amylase is utilized in the pro¬
duction of maltose and maltose syrup. In this case, bacterial debranching
amylase is employed to facilitate the action of p-amylase.
These amylase display their own characteristic action patterns, which
must in some way be related to the structure of their active sites. In view of
the large variety of amylases and action patterns, it seems important to
systematize these action patterns into a unified theory (Keitaro Hiromi, 1989).
The action patterns of amylases may be classified as: (zj cleavage of a-1,
4 and/or a-1, 6 glucosidic linkage, (zz) exo- or endo-type degradation, (zzz)
dependency of hydrolysis rate on the degree of polymerization (DP) (desig¬
nated by n) of the substrate, (iv) cleavage pattern of oligosaccharides, (y)
transglycosylation and condensation activity (apart from hydrolysis, and (vi)
tendency for multiple attack. In case of linear substrates, it is possible to
correlate the action patterns zzz and iv quantitatively with the subsite struc¬
ture of amylase.
Cereals contain two types of amylases, i.e. a and p. The a-amylase is an
endoenzyme that breaks a-1.4 glucose bonds on a nearly random basis.
The enzyme rapidly decreases the size of large starch molecules and thereby
reduces the viscosity of a starch solution or slurry. It will also degrade granular
starch. Amylograph and falling number (both measures of relative viscosity)
have been widely used to measure enzyme activity. Intact cereals have two
levels of amylase. Germination increases the level of a-amylase many times.
The p-amylase is an exoenzyme that attacks starch from the non-reducing
ends of the polymers. It also attacks a-1.4 glucosidic bonds and breaks

15
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

every other bond to release maltose. Because (3-amylase produces maltose,

it is called the saccharifying enzyme. In general, a combination of the two
enzymes results in about 85% conversion of starch to sugar. Unlike a-
amylase, [3-amylase is found in sound intact cereal grains. Germination
does not increase the level of p-amylase. The optimum pH for a-amylase is
about 4.5 and that for p-amylase is slightly higher. The p-amylase is slightly
more susceptible to heat inactivation than a-amylase. The amylase activity
(both a and p) of wheat, barley and rye appeared to be much higher than
that found for the other cereal grains.

PROTEASES

Both proteases and peptidases are found in mature, sound cereals, however
their levels of activity are relatively low. Several methods of determining
proteolytic activity are based upon production of soluble cereal protein, sig¬
nificant amounts of enzyme activity. Wheat flour appears to contain
proteolytic enzyme with pH 4.1 that may be of importance in achieving fer¬
mentation. The peptidases may be important in producing soluble organic
nitrogen that is utilized by yeast during the fermentation.

LIPASES

Although lipases are thought as enzymes that split triglycerides, it is diffi¬

cult to separate their action from that of other esterases. All cereals have
lipase activity, but the activity varies widely within cereal. Oats and pearl
millet have high activity compared with that of wheat or barley.
Lipase activity is important because a free fatty acid is more susceptible
to oxidative rancidity than is the same fatty acid in a triglyceride. Free fatty
acids often gives a soapy taste to the product.

PHYTASE

Phytase is an esterase that hydrolyzes phytic acid. Some question exists as

to whether there is a specific phytase or only phosphoesterases. Phytic acid
is inosital hemaphosphoric acid, and the enzyme converts it to inositol and
free phosphoric acid, which perhaps chelate divalent ions and keep them
from being absorbed in the intestinal tract. Thus the enzyme activity is
important, as it converts a detrimental entity into inositol (a vitamin) and
nutrients.

LIPOXYGENASE

Lipoxygenase catalyzes the peroxidation of polyunsaturated fats by oxygen.

16
 FOOD ENZYMES

The enzyme is rather widespread and bound high concentration in soybean.

It is also found in many other cereals. Soybean lipoxygenase attacks
triglycerides, whereas wheat lipoxygenase must have free fatty acids to be
active. The enzyme has a number of effects on wheat-flour doughs. For
example, it is an effective bleaching agent; a coupled oxidation destroys the
yellow pigments in wheat flour. This is beneficial in bread dough, but a
negative factor in other products. Most durum wheats have been selected to
have low lipoxygenase activity. The enzyme also increases the mixing stability
of wheat-flour doughs and alters dough rheology to produce a strong dough.

PECTIC ENZYMES

Pectic enzymes occur in higher plants and are synthesized by microorgan¬

isms. Their substrate is a variety of pectic substances which occur as struc¬
tural polysaccharides in the middle lamella and the primary cell-wall of
higher plants. Native pectic enzymes can therefore produce important tex¬
tural changes in fruits and vegetables during storage and processing opera¬
tions. Microbial pectic enzymes are important in plant pathology; they are
also produced on a large scale as a processing aid for the food industry.
Consistency changes during ripening and storage of fruit and vegeta¬
bles are often linked to pectic changes which in turn can be ascribed to
pectic enzymes. There are indeed many changes in proteolytic activity ac¬
companying or causing such changes, but the actual mechanism of cell-
wall softening of fruit is still a matter of conjecture.
The presence of pectic enzyme in citrus fruits is responsible for one of
the best studied enzymic phenomena.
Solutes and ions tie up water in solution. Therefore an increase in the
concentration of dissolved substances such as sugars and salts is in effect a
drying of the material. Not only is water tied up by solutes, but water tends
to leave the microbial cells by osmosis if there is a higher concentration of
solute outside the cells than inside. Crystallized is usually unavailable to
micro-organisms. The water activity of water-ice mixtures (vapour pressure
of ice divided by vapour pressure of water) decreases with a decrease in
temperature below 0°C. The aw values of pure water are 1.00 at 0°C, 0.953
at -5°C, 0.907 at -10°C, 0.846 at -15°C, 0.823 at -20°C, and so on. In a
food, as more ice is formed, the concentration of solutes in the unfrozen
water is increased, lowering its aw.
Each micro-organism has a maximal, optimal, and minimal aw for growth.
This range depends on factors discussed below. As the aw is reduced below
the optimal level, there is a lengthening of the lag phase of growth, a de¬
crease in the rate of growth, and a decrease in the amount of cell substance
synthesized—are changes that vary with the organism and with the solute
employed to reduce aw (Stewart and Amerine, 1982).

17
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Water is a major component of foods. However, it is not the total water

content, but the nature, state or its availability that determines the quality
and behaviour of foods during processing and storage. Water activity (aw)
has been shown to be a critical factor in influencing the above.
Water activity (aw) is defined as the ratio of the moisture : vapour pres¬
sure of the food divided by the vapour pressure of pure water, both at the
same temperatures. Values in food vary from close to 1.0 down to a low 0.2
for the very dry foods. Minimum aw for microbial activity varies with the type
of organisms, the chemical composition of the food, chemical preservatives,
pH, oxygen level and other as yet unknown factors (Troller and Christian,
1978).
The water requirement is best expressed in terms of available water or
water activity (aw), the vapour pressure of the solution (of solutes in water in
most foods) divided by the vapour pressure of the solvent (usually water).

REFERENCES

Keitaro Hiromi. 1989. Enzymes in food processing developments in food science. Proceedings
of the Fifth International Congress of Food Science and Technology.
Stewart, G.K. and Amerine, M.A. 1982. Introduction to Food Science and Technology, edn 2.
Academic Press, New York, London.
Troller, J. and Christian, J.H.B. 1978. Water Activity and Food. Academic Press, New York.

LEARNER’S EXERCISE

1. Explain the role of food enzymes in food processing?

2. Write short notes on following: protease; lipase; phytase.
3. Explain the role of any five enzymes in food processing.

18
 Colloidal
system ■

C olloids were first recognized by Graham, who observed that the small
molecules in a solution pass through a membrane whereas materials
like gelatin and glue do not. Some foods consist of one or more dispersed or
discontinuous phases in a continuous phase. The type of dispersed parti¬
cles in food includes crystals, amorphous solid matter, cell fragments, cells,
liquid droplets and gas bubbles. In most cases, the continuous phase is
water or an edible oil. The materials that pass through the membrane are
called crystalloids and the retained particles are called colloids (Belle, 1955).
Colloid chemistry is sometimes called surface chemistry because many of
the properties of colloids are due to their enormous surface area. Any prop¬
erty characteristic of the surface area of a substance increases greatly in
colloidal state. One of the properties of colloidal particles is their ability to
attract and hold other substances on their surface, a process known as
adsorption.
Colloidal particles are called the disperse phase and the material in
which they are held is called the continuous phase. Colloids exists in ‘8’
forms (Belle, 1955). Types of diphasic colloidal dispersion of foods is given in
Table 1.
Table 1. Types of diphasic colloidal dispersion in foods

Disperse phase Continuous phase Common name Example

Liquid Gas Fog, mist, aerosol

Solid Gas Smoke, dust, aerosol
Gas Liquid Foam Beaten egg, white whipped cream,
carbonated water
Liquid Liquid Emulsion Mayonnaise milk
Solid Liquid Suspension Starch in water, paint
Gas Solid Foam rubber, marsh mallow
Liquid Solid Wet sponge gels
Solid Solid Coloured glass vat dried fibre,
certain alloys

Colloid chemistry deals with dispersed systems of a definite size since it

is the size of particles in the colloidal range or zone that imparts the specific
and characteristic properties which are not explained by the laws governing
solid, liquid or gaseous states of matter. Food dispersions may be broadly
divided into five groups, viz. (i) solids in liquid, e.g. gelatin dissolved in water,

19
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

(it) one liquid in another insoluble liquid, e.g. water-in-oil emulsion,

(in) gas in liquid e.g. foam, (iv) gas in solid e.g. solid foam (foam candy), and
(n) solid in gas, e.g. solid aerosol (smoking of meat and fish).
The colloid range lies between that of crystalloidal systems and coarse
suspensions. The lower limit for the size of colloidal particles is given as
1 mfi, the upper limit is 0. Ip (Ruth, 1962).

SOLS

Sols look like solutions, but differ in that the dispersed particles are of
colloidal size. Characteristic differences of true solutions, sols and suspen¬
sions are given in Table 2.
Table 2. Characteristic differences of true solutions, sols and suspensions

True solutions Sols Suspensions

In molecular sub-division In colloidal sub-division In mechanical sub-division

Particles are not visible with Refracted light of particles is Particles visible with ordinary
ultra microscope visible with ultra microscope microscope or naked eye

Particles less than 1 mp Particles from 1 mp to 0.1 p Particles greater than 0.1 p

Formation of gels is not Formation of gels is Formation of gels is not

characteristic is characteristic characteristic

Transparent Transparent Generally opaque

Particles pass through Particles or micelles pass Particles do not pass through
parchment membranes through high-grade filter high-grade filter paper
paper, but not parchment

Intense kinetic movement Less kinetic movement Little movement

more, brownian movement

Systems show high Systems show low Systems show to measurable

osmotic pressure osmotic pressure osmotic pressure

Colloids that resemble solutions are called Sols, whereas those behave
like elastic solids are called gels.

REPRODUCING SOLUTIONS AND SOLS

Solution can be reproduced if its temperature, pressure and concentration

are known. To reproduce sol, it is also necessary to know the size of the
dispersed particle.
Colloids can be prepared by reducing the size of large particles or by
 COLLOIDAL SYSTEM

increasing the size of small particles until they are of colloidal size. Colloids
can be prepared by dispersion or condensation methods. Certain substances
like gelatin, caesin and egg albumin, form colloids when water is added. By
using chemical, mechanical, electrical energy such as vigorous grinding,
mixing at high speeds, or forcing a liquid through a very small opening,
colloids can be prepared.

Stabilization
Material in the colloidal state can be stabilized by adsorption of some¬
thing that prevents the colloidal particles from coalescing. The material
adsorbed may be the solvent electric charge or a surface-active agent.

Adsorbed solvent
A film of adsorbed solvent keeps the dispersed particles in the colloidal
state by preventing them from forming large aggregates and finally precipi¬
tating. Colloids in which the solvent is readily adsorbed are called lyophytic
and those in which there is no attraction between the two phases and there¬
fore no adsorbed layer of solvent, are called lyophobic. When water is the
solvent the corresponding terms are hydrophilic and hydrophobic.

Electric charge
The surface of colloidal particles has an electric charge, because of the
adsorption of ions or because of the ionization of groups within the particle
such as the carboxyl and amino groups of proteins. An electric charge helps
stabilize the colloid, as it helps them to repel each other and thereby pre¬
vents their precipitation. The colloidal particles can have either a positive or
a negative charge and are usually surrounded by ions of opposite charge
which create a double layer. The electric charge can be neutralized by the
addition of acid or base. The point of electric neutrality is called the iso¬
electric point and is expressed as pH. Neutralization of the electric charge
makes a colloid unstable and therefore less soluble. Each protein has a
characteristic iso-electric point (Table 3).
Table 3. Iso-electric points of some food proteins

Protein Iso-electric point (pH)

Casein 4.55
Egg albumin 4.55-4.90
Gelatin 4.80-4.85
p-lacto globulin 5.2
Myosill 6.2-6.6
Gliadin 6.5

At the iso-electric point, proteins coagulate easily because of reduced

stability.

21
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

SURFACE ACTIVE OR WETTING OR

EMULSIFYING AGENTS

These are important in stabilizing foams and emulsions. The molecules of

such agents arrange themselves on a surface with the water-soluble end
(polar group) of the molecule in water and the other end (non-polar group)
in the other phase, which in foods is likely to be air or oil.
Emulsifying agents are substances whose molecules contain both a
hydrophilic or water-loving group and a hydrophobic or water-hating group.
The hydrophilic group is polar and is attracted to the water, whereas the
non-polar hydrophobic group, which is frequently a long chain hydrocarbon
group, is attracted to the oil. Thus in a water-oil (w/o) emulsion the emulsi¬
fier is adsorbed in such a way that the polar heads of the emulsifier mol¬
ecules are in the water and the non-polar tails stick to the oil as shown in
Fig. 3 (Brain etal, 1987).

The type of emulsion formed by an oil-water system depends on a number

of factors including the composition of the oil and water phases, the chemi¬
cal nature of the emulsifying agent and the proportion of oil and water
present. If the polar group of an emulsifier is more effectively adsorbed than
the non-polar group, adsorption by the water is greater than by the oil. The
extent of adsorption at a liquid surface depends on the surface area of liquid
available and increased adsorption of emulsifier by water. This is favoured
by the oil-water interface becoming convex towards the water, thus giving
an oil-water emulsion. The relative proportion of oil and water also helps to
determine whether an oil-water or water-oil emulsion is formed.
The emulsifying agents form a protective coating around the droplets
and reduces surface tension of the emulsions. Oil and water, the constitu¬
ents of most food emulsion, separate soon after they are mixed but form a

22
 COLLOIDAL SYSTEM

stable emulsion if an emulsifying agent is added such as egg yolk for may¬
onnaise or pectin or vegetable gum for certain types of French dressing.

EMULSIFIERS

An emulsion is a two phase system consisting of two immiscible liquids, the

one being dispersed as fine particles in another, e.g. lecithin, cholesterol
and glycerol mono fatty acid esters act as good emulsifying agents.
Among these, the use of mono- and diglycerides of fatty acids, synthetic
lecithin, propyleneglycol stearate, propylene glycol alginate, methylethyl
cellulose, methyl cellulose, sodium carboxyl methyl cellulose, stearyltartaric
monostearin, sodium sulphoacetate, sorbitan esters and brominated veg¬
etable oils is prohibited in milk and cream. Use of emulsifier in food industry
is given in Table 4.
Table 4. Use of emulsifier in food industry

Emulsifier Applications in food industry

Monoglyceride Margarine, ice-cream, bread, potato products,

(Glyceryl monostearate-GMS) snack foods

Diacetyl tartaric acid ester of Tomato juice, tea concentrate, orange juice; in
mono-glycerides (DATE) baking industry as a dough-conditioning agent

Succinylated mono-glycerides In baking industry as a dough conditioner and bread

softener

Calcium stearoyl lactoyl lactate (WL) Whipping agents in egg whites and dehydrated
potato

Sodium stearoyl lactoyl lactate (SSL) In baking industry as dough conditioners and
antistaling agents

Span 60 (scrbitan monostearate), To impart desirable structural characteristics to

Span 80 (sorbitan monoleate), the frozen ice-cream, i.e. ‘stand-up’ properties in
Tween (Poly-oxyethylene sorbitan frozen ice-cream to enable it to be extended into
monostearate) shapes

Polyglycerol esters propylene These emulsifiers (also monoglycerides, SSL, poly¬

glycol monoesters oxyethylene sorbitan esters) are used in bakery
fats or as individual additives to improve cake quality

Increasing and lessening degree of dispersion of substances in food preparation

The methods and the ingredients used in food preparation often bring
about increased or decreased dispersion.
Increasing the temperature may bring about a greater or a lesser degree
of dispersion. Heating of water increases dispersions. Dispersion of fat glob¬
ules in milk is increased by the application of heat to the milk. But when

23
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

proteins are coagulated by heat the degree of dispersion is decreased.

Mechanical dispersion
The grinding of meat, nuts and cereals, stirring and beating are me¬
chanical means of dispersion. Homogenization of milk or cream is a me¬
chanical means of increasing the dispersion of fat particles. Beating egg
white lessens the degree of dispersion, as it brings partial coagulation of the
egg white in the cell-walls surrounding the air bubbles.
Dispersion by acids
The development of acid during the fermentation of bread dough in¬
duces dispersion of the gluten.
Dispersion by alkalies
The addition of alkaline may tend to produce a greater or lesser degree
of dispersion. For example, in breads and cakes and in vegetables, fruits
and milk addition of baking soda increases dispersion.
Dispersion by enzymes
They may also cause an increase or decrease degree of dispersion in
foods, e.g. addition of rennin decreases dispersion of milk and makes the
milk clot and that of proteinase in flour increases the disperion of the glu¬
ten.

COLLOIDAL SYSTEM

Each colloidal solution has its own peculiar properties, depending on the
nature of the particles in solution and the dispersing medium.

Reversible and irreversible colloids

If, after a colloidal solution is evaporated, a sol is reformed upon the
addition of water, the colloid is classified as a reversible colloid, e.g. gelatin
and dried egg white. An irreversible colloid does not spontaneously form a
sol with the addition of water. Reversible and hydrophilic colloids are coex¬
tensive and irreversible and hydrophobic colloids are coextensive.

Hydrophilic and hydrophobic colloids

In colloids the dispersing medium is water. Hydrophilic colloids are solu¬
ble in water, whereas hydrophobic colloids have low solubility in water.
Hydrophilic colloids have high degree of hydration and require large quan¬
tities of electrolytes to coagulate, e.g. hydrophilic colloids (gelation, agar-
agar, starch, pectin and native proteins) and hydrophobic colloids (metal
sols).
The efficiency of emulsifiers and stabilizers in foods depends on bal¬
ance between polar (soluble in water) and non-polar (insoluble in water)
groups.

24
 COLLOIDAL SYSTEM

Effect of electrolyte on hydrophobic colloids

Since the hydrophobic acid is not hydrated, its stabilization depends on
its electric charge. Heating renders the egg hydrophobic, but added salts
are necessary for setting of the custard. The amount of salt required also
varies with the values of cation.
Casein of milk is a good example of a colloid that is little hydrated and
is stabilized by an electric charge. It can remain in the sol form when posi¬
tively or negatively charged. When the charge is neutralized, the casein
flocculates. The charge is neutralized in natural forms, and when it reaches
the iso-electric point of the protein the casein clots (Gortner and Doherty,
1973).

Effect of electrolytes on hydrophilic colloids

Hydrophilic colloids can be reversibly precipitated by high concentra¬
tions of ammonium sulfate and magnesium sulfate, by removing both stabi¬
lizing factors, i.e. the hydration and electrical charge.

Protective and denaturing colloids

A substance in the colloidal state that permits the coagulation of micelles
is called a protective colloid. If too little is used it may sensitize instead of
protecting. The colloid bringing about sensitization is known as a denatur¬
ing colloid.

GELS

Typical gel has a certain amount of rigidity. In gels the dispersion medium
is still liquid but is held in the gel state by the micelles forming a definite
structure, e.g. gels formed by eggs, starch and flour proteins in puddings,
batter and dough products respectively.

Swelling of gels
A solid swells when it takes up a liquid and at the same time (a) it does
not loose its microscopic homogeneity, (b) dimensions are enlarged, (c) its
cohesion is diminished, (d) instead of being hard and brittle it becomes soft
and flexible (Katz, 1933).

Effect of added substances on gel swelling of gels

Addition of acids, alkalies, mineral salts and sugar may increase or
inhibit the degree of swelling. In general, addition of acids and alkalies in¬
creases the swelling of colloidal gels. Salts reduces the degree of swelling
even in the presence of acids or alkalies.

Syneresis
If gels are allowed to stand, protected against evaporation for a number

25
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

of hours, there is a tendency for the gel to separate into two phases. The
liquid may squeeze out of the gel, e.g. separation of whey from curd.

BOUNDARY PHENOMENA

These phenomena play an important role in colloidal reactions. Surface

tension, formation of foams, interfacial tension, adsorption, orientation of
molecules, cohesion and adhesion—all have application in food preparation.

Surface tension
Surface tension is the result of the inherent property of a fluid to tend to
form a minimum surface under all conditions.
When a substance is dissolved in a pure liquid the surface tension of
the solution may not be changed. Sugar increases the surface tension of
water. Aldehydes, fatty acids, fats, acetone, amines, alcohols, toxins, saponin
and proteins lowers the surface tension.

Interfacial tensions of liquid-liquid

When two non-miscible liquids are poured together, one liquid form a
layer on top of the other, thereby making a liquid-liquid boundary. The less
is the solubility of the two liquids on each other, the greater is their interfa¬
cial tensions, but most liquids are not completely insoluble in each other.

Adsorption
The adsorption is defined as the concentration of solute in the interfa¬
cial layer, negative adsorption is it’s concentration in the interior or vice
versa, e.g. they occur in emulsion and foams and throughout the interface
of mixtures when such substances as fat, sugar, salt, baking powder, flour
and egg, are combined.

Formation of foams
A foam is a dispersed gaseous phase, the dispersing medium often be¬
ing a liquid. Since the substance that lowers surface tension of the liquid is
found in greater concentration in the foam, if the foam is continuously re¬
moved as it is formed, the greater portion of the protein or other substance
is removed. For example, in preparing sorghum molasses, one have to re¬
move severe foaming on the surface. In this way tannins, which would in¬
crease the bitterness of the sorghum proteins and other substances are
removed.

FLUIDITY, VISCOSITY AND PLASTICITY OF COLLOIDAL SYSTEMS

Viscosity is one of the important properties of colloidal systems. Lyophilic

colloids show very high viscosities or even plasticity with very low concen-

26
 COLLOIDAL SYSTEM

trations of the micelles. Colloidal solutions show differences in fluidity due

to differences in structure. Baked products may show differences, though
made from the same materials, because the viscosities of the batters vary
owing to different methods of mixing.

Factors affecting viscosity of hydrophilic systems

These are concentration, temperature, degree of dispersion, solvation,
electrical charge, previous thermal treatment, previous mechanical treat¬
ment, presence or absence of other lyophilic colloids, age of the lyophilic sol,
presence of both electrolytes and non-electrolytes.

Plasticity
It is defined as a property of solids in virtue of which they hold their
shape permanently under the action of small shearing stresses but they are
readily deformed, worked or molded under somewhat larger stresses. Plas¬
ticity is an important property of fats used for cakes, biscuits, and pastry.
Plastic fat has a consistency such that it will form a thin sheet or layer in a
batter or it will retain air bubbles where creamed.

DENATURATION AND COAGULATION OF PROTEINS

Defined as the natural protein whereby it becomes insoluble in solvents in

which it was previously soluble (Wu, 1931).
Denaturation may be brought about in many ways. Among the physical
means are: heat, surface force, freezing, pressure, sound wave, and irradia¬
tion. The chemicals used for denaturation of protein are urea, guanidine,
salts, acetamide, formamide, some detergents, H and OH ions, and organic
solvents. Most of the chemical agents are not used in food preparation,
except alcohol in wines. Some proteolytic enzyme may have denaturing ef¬
fects (Bancraft, 1981). Heat also causes denaturation of protein in foods
such as meat, fish and eggs. The salts, and their concentration as well as
the preservative sugar have some influence in heat coagulation of proteins.
Sugar elevates the temperature for coagulation of egg protein. Dextrose and
certain salts are said to disperse heat coagulation of proteins. Increase in
pH such as in deteriorated egg white, requires a higher temperature to co¬
agulate than the fresh egg white (Neurath et al, 1944).
Freezing: Freezing temperature influences the rate and extent of dena¬
turation. Pressure may develop to such an extent in a large piece of frozen
meat that it may aid denaturation.

Desirable effects
Browning: Browning reaction contributes to the aroma, flavour, and col¬
our of many foods such as ready-to-serve cereals, toffees, roasted coffee,
malted barley and baked goods.

27
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Undesirable effects
The undesirable effects of the browning reaction are known in the sugar
beer and malting industries. Many food products may be affected. These
include dried foods such as milk, eggs, fruits, fruit juices, meat, fish, coconut
and vegetables, and canned products, viz. milk, fruits, fruit juice, and juice
concentrates etc. Off-odours, off-flavours and off-colours develop in these
foods. Off-flavour may be mild, stale or become very bitter. The colour may
vary from light cream to nearly black. Coconut develops a saffron colour.
Use of S02 is the best method for prevention of browning in dried fruits,
vegetables and coconut. Low temperature and low moisture content of the
products, and acidity delays the appearance of the brown colour. The C02
or N2 does not delay the reactions (Barnes and Kaufman, 1947).
Loss of nutritive value may occur (z) when the amino acids or proteins
are heated with glucose or other sugars, (zzj when baked products such as
bread and cake are subjected to high temperatures during baking (crust) or
when toasted, and (in) by storage of food products (Patton etal, 1948), e.g.
loss of biological value of the protein by refluxing casein and glucose, loss of
lysine, arginine and tryptophan by heating soybean meal and reducing pro¬
tein efficiency ratio (PER) on toasting and browning a cake mix.

REFERENCES

Bancraft, W.D. and Rutzler, J.E (Jr). 1981. The denaturation of egg albumin. Journal of Physical
Chemistry 35: 144.
Barnes, H.M. and Kaufman C.W. 1947. Industrial aspects of the browning reaction. Industrial
Engineering Chemistry 39: 1,167.
Belle L.W. 1955. Experimental Cookery from the Chemical and Physical Stand Point. John Wiley
& Sons, Inc. New York; Chapman & Hall Ltd, London.
Brian, A., Fox Allan and Cameron, G. 1987. Food Science—a Chemical Approach. Unibooks
University of London Press Ltd, London.
Gortner, R.A. and Doherty, E.H. 1973. Hydration capacity of gluten from strong and weak
flours. Journal of Agronomic Research 13: 389.
Katz, J.R. 1933. The laws of swelling. Trans Faraday Society 29: 279.
Neurath, H., Greenstein, J.P., Putman, F.W. and Erickson, J.O. 1944. The chemistry of pro¬
tein denaturation. Chemical Reviews 341: 157.
Patton, A.R., Gill, E.G. and Foreman, E.M. 1948. Amino acid impairment in carein heated
with glucose. Science 108: 559.
Ruth, M. G. 1962. The Experimental Study of Foods. Houghton Mifflin Co., Boston.
Wu, W. 1931. Studies on denaturation. XIII. A theory on denaturation. Chinese Journal of
Physiology 5: 321.

LEARNER’S EXERCISE

1. Why a colloidal system is important in food chemistry?

2. Write characteristic differences between true solutions, sols and suspensions.
3. What factors affect gel formation?
4. Write about iso-electric pH. Mention iso-electric point of casein, egg albumin and gelatin.
5. What are the emulsifying agents?

28
 COLLOIDAL SYSTEM

6. Enumerate the role of emulsifiers in food industry.

7. Write short note on Gelatin.
8. Differentiate the following:
(a) Enzymatic and non-enzymatic browning.
(b) Denaturation and coagulation.
(c) Viscosity and plasticity.
(d) Absorption and adsorption.
(e) Surface tension and interfacial tension.

29
6. Food
additives

F ood additives may be defined as non nutritive substances added inten¬

tionally to food generally, in small quantities to improve its appearance,
flavour, texture or storage properties. Need and wants of the consumer dictate
the use of additives in industry. The legal meaning of the term food additive
differs significantly from country to country. The USA Federal Food Drug
and Cosmetic Act approved on 25 June 1936 and is currently amended. A
food additive is a substance or a mixture of substances, other than a basic
food stuff, which is present in a food as a result of any aspect of production,
processing, storage or packaging. The term does not include chance con¬
tamination.
Among food additives some are used to colour foods, others to bleach
them, some add flavour to food, others remove flavours, some make food
firmer, others soften them, some keep foods dry, others keep moist, some
thicken foods, others keep them from thickening, some produce foams, oth¬
ers prevent them, some make foods acidic, others make alkaline, still others
suspend particals, some are oxidizing agents,others are reducing agents,
some hasten chemical changes, others retard them. Sometimes one food
additive has more than one function (Achaya, 1981).
Use of additives in food processing are to maintain of nutritional qual¬
ity, enhancement of keeping quality by the use of antioxidants, antimicro¬
bial agents, inert gases, meat cures etc. Food additives are used for the
enhancement of attractiveness of foods by means of colouring and flavour¬
ing agents, emulsifiers, stabilizers, thickeners, clarifiers and bleaching agents.

BROAD CLASSES OF INTENTIONAL FOOD ADDITIVES

The intentional food additives may be classified under 12 broad groups:

1, preservatives; 2, antioxidants; 3, sequestrants; 4, surface active agents;
5, stabilizers and thickeners; 6, bleaching and maturing agents, starch modi¬
fiers; 7, buffers, acids and alkalies; 8, food colours; 9, non-nutritive and
special dietary sweetners; 10, nutrient supplements; 11, flavouring agents;
and miscellaneous (Bender, 1988).

Preservatives
These include chemical preservatives against bacteria, yeasts, and
moulds. Sodium benzoate is used in soft drinks and acidic foods; sodium

30
 FOOD ADDITIVES

and calcium propionates in breads and cakes as a mould inhibitor; sorbic

acid on cheese; and compounds of chlorine as a germicidal wash for fruits
and vegetables. The preservatives also include fumigants such as ethylene
oxide and ethyl formate, used to control micro-organisms on spices, nuts,
and dried fruits. Preservatives which control browning of fruits and vegeta¬
bles caused by enzymes such as sulphurdioxide (S02) are also included
(Arya, 1987).
All preservatives are not permitted in all foods. Preservatives along with
the food items in which their addition is permitted are given in Table 5
(Ennahrung, 1984).

Table 5. Preservatives permitted in food items

Preservative Concentration Foods

Sulphurdioxide or salts of 49-3,000 ppm Sausages, fruit pulp, fruit juice concentrate, squashes,
sulphurous acid crushes, jams, syrups, cordial, sugar, glucose,
khandsari, corn flour and syrup, beer, cider, pickles,
dehydrated vegetables, wines, ready-to-serve bev¬
erages, hard boiled confectionery

Propionic acid and its salts 5,000 ppm Bread

Benzoic acid and its salts 50-6,000 ppm Syrups, squashes, james, jellies, ready-to-serve bev¬
erages, pickles, chutney, ginger beer, tinned caviare

Sorbic acid and its salts 1,000-1,500 ppm Cheese, bread, flour confectionery, smoked fish
wrappers

Nisin 1,000 ppm Cheese

Nitrites 200 ppm Cooked pickled meat, ham and bacon

Nitrates 500 ppm Cooked pickled meat, ham and bacon

Antioxidants
These include the compounds used to prevent oxidation of fats in many
processed foods such as potato chips, breakfast cereals, salted nuts, bis¬
cuits and crackers and many other fatty foods, which could not be stored for
any length of time on supermarket shelves without developing rancidity.
The important antioxidants are butylated hydroxy anisole (BHA),
butylated hydroxy tolune (BHT), propyl gallate, nordihydro guiaretic acid
(NDGA), tocopherols and ascorbic acid.

Sequestrants
These are chelating agents or sequestering compounds. They react with
trace elements such as iron and copper present in foods and remove them
from solution. The trace elements are active catalysts of oxidation and
discolouration of food products. Sequestrants such as ethylene diamine tetra

31
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

acetic acid (EDTA), poly phosphates and citric acid react with trace ele¬
ments and inactivate them.

Surface-acting agents
These include the emulsifiers used to stabilize oil in water and water in
oil mixtures, gas in liquid mixtures and gas in solid mixtures. In addition to
emulsifiers of natural origin such as lecithin, and emulsifiers that can be
prepared synthetically such as mono and diglycerides and their derivatives,
and other agents include certain fatty acids and their derivatives, and bile
acids are important in digestion. Surface-active agents exert a variety of
effects such as emulsifiers, wetting agents, solubilizers, suspending agents,
complex agents.

Bleaching and maturing agents and starch modifiers

Freshly milled flour has a yellowish tint and suboptimum functional
baking qualities. Both the colour and baking properties improve slowly in
normal storage. These improvements can be obtained more rapidly and with
better control through the use of certain oxidizing agents. Benzyl peroxide
is an oxidizing agent which bleaches the yellow colour. Oxides of nitrogen,
chlorine dioxide and other chlorine compounds both bleach colour and
mature the flour.
Oxidizing agents such as hydrogen peroxide also are used to whiten the
colour of milk for certain kinds of cheese manufacture and to bleach. Bromate
and iodate-oxidizing agents are also used to condition bread doughs for
optimum baking performance. Starch modifiers include compounds such
as sodium hypochlorite which oxidize starches to a higher degree of water
solubility.

Flavouring agents and flavour enhancers

The flavouring agents include both natural and synthetic flavours. Some
of the natural flavouring substances include spices, herbs, essential oils
and plant extractives. Typical of the synthetic flavour additives are
benzoldehyde (cherry), ethyl butyrate (pineapple), methyl anthranilate (grape)
and methyl salicylate (winter green).
Currently there are more than 1,200 different flavouring materials used
in foods, due to the ever-increasing variety of different foods, including foods
of international character. But the increasing use of added flavours also
must be attributed to the need to replenish flavours partially or completely
lost, by various modern processing methods involving heating, concentrat¬
ing, drying and other food-handling practices.

Flavour enhancers or potentiators

These compounds do not have flavour but intensify the flavour of other
compounds present in foods. Monosodium glutamate and 5'-nucleotides
are commonly used.

32
 FOOD ADDITIVES

Non-nutritive dietary sweetners

The well-known substance is saccharin. Saccharin is permitted as a
sweetner in food preparations and soft drinks for diabetic subjects. In 1972
FDA, USA, recommended that the daily intake of saccharin by an adult
should not exceed 1 g, as the studies have shown that rats receiving sac¬
charin developed bladder tumours.

Nutrient supplements
Principal among these are the vitamins and minerals added as supple¬
ments and enrichment mixtures to a number of products. Important exam¬
ples are: vitamin D added to milk; B vitamins, iron and calcium added to
cereal products; iodine to salt; vitamin A to margarine; cheeses made from
bleached milks; dietary infant formulas; and vitamin C to fruit juices and
fruit-flavoured desserts.

Miscellaneous
Solvents of various types are used in manufactured foods and drinks
(IARC, 1988). Dichloromethane and trichloroethylene, which have been used
for the decaffeination of coffee and tea fat. Substitutes were first introduced
into food supplies in 1993. They are regulated not as additives but as food
ingredients or as novel foods (World Cancer Research, 1997).

Food colours
Colours are added to many food items, to improve their appearance and
to give the public appetizing and attractive qualities they desire. Colours
from natural materials such as annatto, caramel, carotene and saffron are
the best examples. Colours of synthetic origin which include coal tar dyes
have been examined for their safety. Synthetic colours generally excel in
colouring power, uniformity, stability and lower cost.
Carbonated beverages, candies, gelatin desserts and bakery goods are
among items coloured with certified coal-tar dyes. Food colours also include
inorganic materials such as iron oxide to give redness and titanium dioxide
to intensify whiteness.
In India 12 natural pigments, their extracts of synthetic equivalents,
viz. beta-carotene, beta-apo-8-carotenal, methyl ester of beta-apo-8-
carotenoic acid, ethyl easter of beta-apo-8-carotenic acid, canthaxathin,
chlorophylls, riboflavin, caramel, annatto, ratanjot, saffron and cucurmin
(turmeric) are permitted to be added in foods. Among the synthetic dyes, 11
permitted colours are given in Table 6.

Stabilizers and thickeners

These include gums, gelatin, starches, dextrins, protein derivatives and
other additives that stabilize and thicken foods by combining with water to
add viscosity and to form gels. Gravies, pie fillings, cake toppings, chocolate
milk drinks, jellies, puddings and salad dressings are among the many foods

33
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Table 6. Permitted food colours

Natural or synthetic equivalent Artificial synthetic dyes

p-carotene Panceair42
p-apo-8'-carotene Carmosine
Esters of p-apo-8'-carotenic acid Fast red E
Amaranth
Canthaxanthin Erythrosine
Chlorophyll Tartazine
Annatto Sunset yellow
Caramel Indigo carmine
Rat an jot Brilliant blue
Saffron Green
Curcumin (turmeric) Fast green

that contain such stabilizers and thickeners as gum arabic, carboxy methyl
cellulose, carrageenan, pectin, amylose, hydrolysed vegetable proteins, gelatin
and others.

SAFETY OF FOOD ADDITIVES

Safety in using an additive is an important consideration. International ac¬

ceptance of food additives is given in Fig. 4.
• It is impossible to establish absolute proof of the non-toxicity of a
specified use of an additive for all human beings under all condi¬
tions; critically designed animal tests of the physiological, pharma¬
cological and biochemical behaviour of a proposed additive can provide
a reasonable basis for evaluating the safety use of a food additive at
a specified level of intake.
• It is generally felt that the presence of harmful impurities in food
additives can be excluded most effectively by the establishment of
specifications of purity.
• It is agreed that the amount of an authorized additive used in a food
should be the minimum necessary to produce the desired effect. The
limit should be established with due attention to the following fac¬
tors:
(a) The estimated level of consumption of the food or foods for which
the additive is proposed.
(b) Minimal levels which in animal studies produced significant de¬
viations from normal physiological behaviour.
(c) An adequate margin of safety to reduce to a minimum any haz¬
ard to health in all groups of consumers.
• For all people, legal control over the use of food additives is essential.
This is best accomplished through the use of a permitted list, which

34
 FOOD ADDITIVES

Request for
consideration
Supply of data
Requests for
consideration
Commodity Committees of Decision reached
the Codex Alimentarius

Fig. 4. Flow diagram for international acceptance of food additive (Source: Ferrando, 1981)

35
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

effectively prevents the addition of any new substances to food, until

an adequate basis for judgement of their freedom from health hazard
has been established.
• As a matter of principle, food-label declaration informing the con¬
sumers of the presence of additives in the product, has been found to
be the most effective method of achieving this result.
• Regulations governing the control of food additives are useless, unless
the laws can be enforced. Trained food inspectors, food-control labo¬
ratories and reliable analytical methods are of utmost importance.

REFERENCES

Achaya, K.T. 1981. Regulatory aspects of food additives. Indian Food Packer 35 (May-June):
11-14.
Arya, S.S. 1987. Role of food additives in convenience foods. Indian Food Industry 6 (Jan-
March): 11-16.
Bender, A.E. 1988. Food additives. Practitioner; 232 1442 143-47.
Ennahrung. 1984. Effects of preserving foods using additives of plant origin. Food Engineering
82: 81-83.
Ferrando, R. 1981. Traditional and Non-traditional Food. Food and Agriculture Organization of
United Nations, Rome.
IARC. 1988. Monograph on the Evaluation of Carcinogenic Risks to Human : Alcohol Drinking.
International Agency for Research on Cancer.
World Cancer Research. 1997. Food Nutrition and the Prevention of Cancer: a Global Perspec¬
tive. American Institute for Cancer Research, Washington.

LEARNER’S EXERCISE

1. Discuss the importance of food additives in food preservation.

2. What is food additive and explain the classification of food additives.
3. Write short notes on:
(a) Permitted food colours
(b) Permitted food preservatives
(c) Bleaching and maturing agents
(d) Starch modifiers
4. Represent schematically, the international acceptance of food additives.
5. Write about the following briefly:
(a) Antioxidants
(b) Sequestrants
(c) Flavouring agents
6. Explain the role of chemical additives in fruit preservation.
7. What are the various food additives and their use in day-to-day life?
8. What is the role of salt and sugar in food preservation?
9. Define food additive and write briefly about three food additives which are used in pres¬
ervation.

36
Part II

Food safety, quality

and evaluation
 Evaluation of ~7
food (

M ost of us enjoy the pleasure of eating a wide variety of foods. Evalua¬

tion is an important part of the process of developing new food prod¬
ucts and of analysing the market potential for these foods, likewise it is
necessary in the study of processing and storage effects. The student of food
science must be able to evaluate food products prepared in the laboratory to
understand effects of various food preparation and processing procedures
on these foods. The research emphasis in the food industry has been normaly
on economical preparation and distribution of safe and nutritious foods.
The food scientists must be able to evaluate these properties in order to
assure that quality has been achieved. Evaluation provides information per¬
tinent to the quality of a food product involving chemistry, physics, technol¬
ogy of the food, its degree of excellence, which encompasses taste, aroma2
texture, appearence, and nutritional content, as well as factors that deter¬
mine the safety of food.
When the food is evaluated by the use of human sensory organs, the
food is being subjectively evaluated. When assessment is done with the use
of instruments that do not involve the human senses, the food is said to be
objectively evaluated. Objective measurements of food are preferable to sub¬
jective measurements only if the objective tests can provide a precise meas¬
ure of a sensory quality.
The important senses by which man perceives his foods are sight, smell,
taste, touch, kinestheses, temperature and pain. These senses are often not
noticed. We are usually not aware of the differences among taste, feel, and
odour sensations when we bite into a food. For most people wining and
dining are among the enjoyments of life. To be enjoyed, food must be of
good-eating quality or palatability. The palatability of food may be judged on
the basis of the kinds, quality and intensity of sensory impressions made.
The most important sensory properties of food are flavour (comprising
taste and odour), temperature (sensations of heat and cold), appearance
and texture or mouth-feel (affecting the senses of touch).
The art of food preparation, small or large scale, is the art of skilful
combination of these properties to please the eye, the nose and the palate
(George and Maynard, 1973). Flavour is a complex of sensations that we
derive from food, including particularly the sensations of taste and smell. If
we have a cold, our flavour sensations are often blunted, because the smell
or olfactory apparatus is temporarily out of action.

39
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

The basic requirements for all sensory testing facilities are (z) food prepa¬
ration area, (zz) separate panel discussion area, (z'zz) quiet panel booth area,
(iv) desk or office area for the panel leader, and (z;) supplies for preparing
and serving samples.
Scientific methods of sensory analysis of foods are becoming increasingly
important in assessing the acceptability of food products. There are two
main groups of methods of sensory evaluation, (a) analytical or objective
methods (difference, ranking and quality tests) and (b) hedonic or subjective
methods (preference, consumer and market tests). The different methods of
sensory analysis are given in Table 7 (Swaminathan, 1988).

Table 7. Main methods of sensory evaluation

Analytical or objective method Hedonic or subjective method

Difference tests Preference tests

Single sample test (A note-A test) Paired preference test
Paired difference test Triangle preference test
Triangle difference test
Duo-trio test
Ranking tests Hedonic scale
Quality tests
Scoring tests
Descriptive tests
Flavour profile method
Dilution flavour profile method

SUBJECTIVE EVALUATION

Human sense organs for taste, smell, sight, touch and hearing are the ways
for subjective evaluation of food. People participating in sensory evaluation
may be untrained consumers or trained laboratory-taste panelists. Groups
of consumers are usually used in preference testing to learn if a good prod¬
uct will be acceptable, the results of which are useful to food manufacturers
in predicting whether or not consumers will buy a particular new product.
Consumer panels are usually composed of a large number of individuals—
often more than 100 people selected from a geographical area—represent¬
ing the general consumer population.
A trained laboratory panel is commonly used for difference testing, scor¬
ing or ranking. Panel members should be readily accessible to the testing
laboratory and be in good health. Training increases sensitivity and memory,
permitting more precise judgements and more uniform results. The amount
of training given to panel members depends on the degree of accuracy re¬
quired for the testing. Judges may be testejd for their ability to recognize the
four basic tastes—sweet, salty, sour and bitter.
The threshold for each of the basic tastes may be determined by having

40
 EVALUATION OF FOOD

the subject taste, a series of solutions which gradually increase in concen¬

tration of a substance that elicits the taste. The threshold is the concentra¬
tion at which the subject can first detect that the solution is different from
water. The sex of the panelists as well as smoking habits have little influ¬
ence on ability to discriminate tastes, but there is some effect of age on
flavour sensitivity, particularly after age of 50 years.
A special testing area should be used for sensory evaluation of food, so
that conditions such as lighting, temperature, atmosphere and humidity
can be carefully controlled. The testing area should be separated from the
food preparation area, and the judges should be separated from each other
for independent judgement.
Sensory evaluation is as scientific discipline used to evoke, measure,
analyse and interpret reactions to these characteristics of foods that are
perceived by the senses. The various approaches employed in sensory test¬
ing of food include the use of the following tests.

Paired comparison
The judge is given two samples and requested to indicate how they
differ in a particular sensory characteristics. This test is useful in selection
and training of a panel. It is also valuable in programmes to control and
maintain the quality of a food product. However only two samples can be
compared at one time, at times necessitating a large number of compari¬
sons.

Triangle test
Three samples are presented simultaneously, two of which are identi¬
cal. The judge must decide which two of the three samples are alike and
which is the odd one. This test has similar advantages and disadvantages to
paired comparisons, and is particularly useful when only small differences
exist between samples.

Duo-trio test
One identified sample is presented first. Two coded samples are then
presented, one of which is identical to the first sample. The judge must
determine which of the two coded samples is like the first control sample.
With this test there is 50% chance of a correct answer simply by guessing.
In many cases the paired comparison and triangle tests may be more useful
than the duo-trio test.

Ranking
Several samples are presented simultaneously, and are ranked by the
judge according to the intensity of a single sensory characteristic. This test
is useful when a comparatively large number of samples are being evalu¬
ated at one time for a single quality characteristic.

41
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Scoring
The judge rates samples according to a set of numerical standards.
Standards may consider the relative importance of particular properties
such as colour, texture, and flavour in formulating an overall score. Scoring
is called hedonic when the degree of liking is expressed on a scale of five to
nine points, ranging from extreme disapproval to extreme approval.-Much
information about the test product can be accumulated as scoring allows
the collection of both qualitative and quantitative data. This type of evalua¬
tion may be difficult for an inexperienced person who does not have well-1
established standards by which to judge.

Flavour profile method

A specially trained panel works together in producing written record of i
the aroma and flavour of a product. Aroma and flavour are examined sepa¬
rately and tabulated according to (i) individually detectable components or
character notes, (n) intensity of each, (in) order of appearance, (iv) aptitude
and (v) the after taste. This method requires a highly skilled panel that
works well together. The information collected may be difficult to interpret
and analyse for purposes of research.

OBJECTIVE EVALUATION

Because sensory evaluation of food is time-consuming and costly, less ex¬

pensive methods of analysis with laboratory instruments are desirable pro¬
vided they give information that correlates well with the sensory
characteristics. Objective evaluation involving instruments may be catego¬
rized into two types, viz. imitative measures and non-imitative measure¬
ments. Imitative measurements are done by instruments which imitate the
way in which humans perceive the sensory property, such as machines that
duplicate the bite of human teeth. Non-imitative measurements include any
determination of chemical or physical properties of a food system that sta¬
tistically correlates with sensory properties when each type of measurement
is performed on a single food product. For example, the taste intensity of a
particular acid solution may be predicted by determining the hydrogen ion
concentration.

Texture measurement
Rheology deals with the deformation and flow of both liquids and solids.
Deformation and flow of food materials are related to their subjectivity per¬
ceived textural properties. For example, the tenderness of meat is subjec¬
tively evaluated by the effort or force required for the teeth to penetrate and
chew the tissue. Fresh fruit is sometimes pressed with the hand and fingers
as an indication of firmness or softness.

42
 EVALUATION OF FOOD

Objective tests for measuring food texture also rely upon deformation
and flow characteristics in determining how much the test sample resists to
applied force which is greater than gravity. Instruments for texture meas¬
urement usually consist of four basic elements.
1. A probe contacting the food sample. This may be a flat plunger, a rod,
a spindle, a pair of shearing jaws, or tooth-shaped attachment, a cutting
blade, or a set of cutting wires.
2. A driving mechanism for putting the probe in motion. The motion
may be verticle, horizontal or rotational at either a constant or a variable
rate.
3. A sensory element for detecting the resistance of the food sample to
the applied force.
4. A recognizing system. This may be a dial showing maximum force, on
oscilloscope, or a recorder tracing.
Each texture-measuring device has advantages and short-comings that
are considered when using it for the evaluation of food. Some instruments
commonly used for measuring the texture of foods are given in Table 8.
Table 8. Instruments used for measuring the texture of foods

Instrument Description

Penetrometer Employs a rod-like or cone-shaped probe to penetrate the

test material

Compressimeter Uses a flat or curved plunger to test the resistance of a food

sample being compressed

Shearing device Uses a single or multiple blade. Probe to shear through a

sample

Cutting device Employs a knife-like blade or wire to cut through the test food

Masticometer Attempts to simulate the condition of mastication or chewing

Consistometer Measures either the distance of spread when a semi-solid

food sample is placed on a flat surface, or the resistance to a
rotating spindle or poddle placed in a liquid food

Viscometer Employs capillary flow or uses a rotated spindle in the test

material

Multiple-purpose units Perform a number of different texture tests

In rheology, three types of deformation are generally recognized, viz.

elastic, viscous and plastic. If a material is perfectly elastic, deformation
occurs instantaneously when force is applied and completely disappears
when the force is released. A fluid in perfect viscous flow exhibits a rate of
flow that is directly proportional to the applied force. Materials that show

43
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

properties of both fluids and solids are called plastic substances. In these
materials a force, called a yield value, must be first applied before flow will
begin. Yield value is shown in Fig. 5.

Fig. 5. Rheological model, (a) Elasticity is represented as a spring; (b) viscosity as a dish pot; and (c) yield
value as a block on a flat surface

Foods are particularly complex materials from a rheological stand point.

They are often heterogeneous and rheological properties may vary from one
place to another within one food product. Most foods cannot be described by
a simple rheological model since they usually passes all rheological proper¬
ties to some degree.

Flavour measurements
No imitative objective procedures are available to measure the taste and
the aroma of food because the processes by which these senses operate are
not fully understood. The closest imitative evaluation of flavour has come
from research studies which measures nerve responses in experimental ani¬
mals that are triggered by stimulating a taste cell.
The gas chromatography, a sensitive laboratory procedure, has been
widely used in the study of chemical molecules that contribute to the aroma
and flavour of foods. Many different molecules may be present in the aroma
from one food. For example, more than 400 components have been detected
in coffee and at least 120 constituents in fresh strawberry odour. A major
task in aroma research is identifying these molecules and determining which
ones are primarily responsible for characteristic aromas. Gas chromatogra¬
phy makes possible the separation and detection of the molecules.
Food quality is a complex concept with properties that include taste,
aroma, texture, appearance, nutritional value and safety.

44
 EVALUATION OF FOOD

REFERENCES

George, F.S. and Maynard, A. Amerine. 1973. Introduction to Food Science and Technology.
Academic Press, New York and London.
Swaminathan, M. 1988. Handbook of Food Science and Experimental Foods. Bangalore Print¬
ing & Publishing Co. Ltd, Karnataka.

LEARNER’S EXERCISE

1. Explain in detail about subjective and objective evaluation of foods.

2. What are the various approaches to be applied in sensory testing of a food product?
3. Write the instruments used for measuring texture of foods.
4. What are the parameters to be considered to evaluate the product developed in the labo¬
ratory?
5. Write short notes on:
(a) Triangle test
(b) Duo-trio test
(c) Ranking test
(d) Paired comparison test
6. Write in brief:
(a) Elasticity
(b) Viscosity
(c) Rheology
(d) Scoring

45
8 Food adulteration,
■ food standards and labelling

F ood is consumed to provide energy and nutrition and as such it should

be wholesome and not have deleterious substances. The food should be
what it is, nature, property and grade of excellence. The quality in a general
term is a measurement of the degree of excellence of a product. The param¬
eters of quality are the grades, standards and specifications laid down by
the government agencies or expert bodies constituted for this purpose.
Adulteration is a term used to designate that a product is not what it
should be, from biochemical, cleanliness and hygienic point of view. To safe¬
guard the interest of the consumer, it is necessary to have a check and
control over the quality of food marketed for human consumption. Consum¬
ers are rightly concerned about the safety, wholesomeness, nutritional ad¬
equacy, palatability and cost of foods, that they buy for their use. The problem
of food-quality control in advanced countries is quite different from that
what exists in a developing country. The farmer is interested for improve¬
ment in nutritional value, hygiene, aesthetic appeal and freedom from ex¬
traneous and harmful contaminants. In a developing country, the concern
is more to prevent intentional adulteration, its detection and punishment of
unscrupulous traders or manufacturers.
There are government agencies in all the countries which look after the
quality-control work by formulating policies, framing standards, laying down
standard procedures for implementing the schemes to achieve the objective
of prevention of adulteration.

“PREVENTION OF FOOD ADULTERATION ACT”

AND RULES IN INDIA

In India “Prevention of Food Adulteration Act” was promulgated by the gov¬

ernment in 1954 and the Rules under this Act were made in 1955 and
many amendments have been made subsequently. The Act was intended to
make provisions for the prevention of adulteration in food. The Act empow¬
ers the government agencies to prevent this unsocial activity and safeguard
the health of the people. The implementation of the Act/Rules is done at
State/Union Territory level, whereas the central government may give such
directions it may deem necessary regarding execution of the provisions in
the Act/Rules. For this purpose, the ‘Central Committee for Food Stand¬
ards’ was constituted with (a) Members representing concerned ministries,

46
 FOOD ADULTERATION, FOOD STANDARDS AND LABELLING

(b) Representatives of consumers, medical profession, agricultural, com¬

mercial and industrial organisations, hotel industry, (c) Representatives of
State/Union Territories, (d) Directors of the Central Food Laboratories and
(e) Director-General of Health Services. Four Central Food Laboratories and
a number of state-level laboratories were established for analysis of sam¬
ples collected by the state-level food inspectors.

ADULTERATED FOOD ARTICLE

A food article is considered adulterated as per the PFA Act and Rules as
follows:
(a) if the article sold by a vendor is not of the nature, substance or
quality which it purports or is represented to be.
(b) if the article contains any other substance which affects or if the
article is so processed as to affect injuriously the nature, substance or qual¬
ity thereof.
(c) if any inferior or cheaper substance has been substituted wholly or
in part for the article, so as to affect injuriously the nature, substance or
quality thereof.
(d) if any constituent of the article has been wholly or in part abstracted
so as to affect injuriously the nature, substance or quality thereof.
(e) if the article has been prepared, packed or kept under insanitary
conditions whereby it has become contaminated or injurious to health.
(f) if the article consists wholly or in part of any filthy, putrid, rotten,
decomposed or diseased animal and vegetable substance or is insect in¬
fested or is otherwise unfit for human consumption.
(g) if the product is obtained from a diseased animal.
(h) if the article contains any poisonous or other ingredient which renders
it injurious to health.
(i) if the container of the article is composed of any poisonous or delete¬
rious substance which renders its contents injurious to health.
(j) if any colouring matter other than that prescribed is present in the
article or if the amounts of the prescribed colouring matter in the article are
above the prescribed limits.
(k) if the article contains any prohibited preservatives or permitted pre¬
servatives in excess of the prescribed limits, and
(l) if the quality or purity of the article falls below the prescribed stand¬
ard.
In considering the case of adulteration, a distinction is made between a
primary food and processed food. Primary food means any article of food
being a produce of agriculture, horticulture in its natural form, e.g. wheat,
maize, apple, plantain, yam etc. Rice is a processed food. Similarly, wheat
flour, fruit products, root starches are processed articles of food.

47
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

STANDARDS UNDER PFA ACT AND RULES

The standards laid down under the PFA Act and Rules are minimum stand¬
ards of purity and are based on the agricultural practices followed, climatic
conditions prevailing, economic conditions and nutritional status of the people
in the country. The standards under the PFA Act and Rules take into con¬
sideration the recommendations made by the international organizations,
viz. FAO and WHO, and technical reports published by reputed research
institutes on the toxicity of various food contaminants. The standards are
mandatory and are enforced by government laws. Articles of food which do
not conform to the standards are considered unfit for human consumption.
The Act and Rules deal with preservatives, poisonous metals, naturally oc¬
curring toxic substances, anti-oxidants, emulsifying and stabilizing agents,
flavouring agents, colouring matter and other food additives, insecticides
and pesticides, solvent extracted oils and edible flours, non-alcoholic bever¬
ages, starchy foods, spices and condiments and their mixes, honey, jaggery,
saccharin, coffee, tea and milk, milk products, edible oils, cereals, baked
products, sweets and confectionary and a range of similar products. The Act
and Rules deal with the administrative procedures to be followed and re¬
porting, analysis, prosecution, presentation of cases in a court of law and
punishment to be carried out.
Examples of common adulterates and simple tests to detect them are
given in Table 9 (Suhasini, 1994); (i) date seed and tamarind seed powder in
coffee powder; (ii) argemone oil, castor oil or mineral oil in vegetable oils; (in)
hydrogenated oil in butter and ghee; (iv) dirt, filth, sand in spices and con¬
diments; (n) resins, gum and starch in asafoetida; (in) extracted fruits in
cardamom and cloves; (nil) oil soluble dyes, added colour, brick powder saw¬
dust in chilli powder; (niii) dung powder in coriander; (be) lead chromate,
metanil yellow in turmeric powder; (a) excessive moisture and sucrose/jaggery
in honey, (xi) water and starch in milk; (xii) khesari dal in pulse; (xiii) iron
fillings in tea, (xiv) colouring matter in split pulses; (xv) chalk powder, dirt in
wheat flour.
Other types of low-grade articles brought under PFA Act and Rules are:
(i) foodgrains having excessive inorganic and organic foreign matter, dam¬
aged foodgrains, weevilled grain, presence of rodent hair and excreta, uric
acid, moisture beyond prescribed limits; (ii) foodgrains having pesticide
residues and aflatoxin beyond permitted limits; (iii) wheat milled products
containing alcoholic acidity, total ash, acid insoluble ash, moisture more
than permitted levels and gluten not less than prescribed percentage;
(iv) vegetable oils not conforming to the specifications, and so on.
The Rules include elaborate definitions and description of different veg¬
etable, fruit and cereal products and also other food items. Restrictions on
additives are mentioned wherever necessary, for example, it is mentioned
that mono-sodium-glutamate should not be added to any food for use by

48
 FOOD ADULTERATION, FOOD STANDARDS AND LABELLING

Table 9. Food adulterants and simple tests to detect food adulteration

Substance Adulterant Tests

1 2 3

Tur dal Lakh dal or metanil 1. Lakh dal is irregular in shape and of lighter col¬
our than tur dal
2. Add concentrated HCI to moisten dal. Yellow
colour will turn into magenta red if metanil yellow
is present
Rawa Iron fillings to add Pass magnet through the rawa. Iron fillings will
weight cling to it
Sago Sand and talcus Pure sago swells and on burning, it leaves hardly
any ash
Bajra Fungus Immerse in salt water, fungi will come on top
Jaggery Metanil yellow HCI added to jaggery solution turns magenta col¬
oured
Bura sugar Washing soda 1. Gives effervescence with HCI if washing soda
is present
2. If dissolved in H20 washing soda will turn red
litmus blue
Ghee or butter Vanaspati Dissolve 1 teaspoon of sugar in 10 ml of HCI. Add
10 ml of melted ghee and shake thoroughly for 1
min. Allow it to stand for 10 min. If vanaspati has
been added the acqueous layer will be red
Coconut oil Any other oil Place a small quantity of oil in refrigerator, coco¬
nut oil will solidify leaving the adulterant as a sepa¬
rate layer
Edible oil Agremone oil On treatment with nitric acid it will give red colour
in acid layer, indicating the presence of argemone
oil
Milk Water Measure specific gravity with lactometer. Normal
reading 1.1030 to 1.034
Tea powder Exhausted tea Sprinkle the powder on a wet white blotting
leaves, dried paper. Spots of yellow and red colour
powder and appearing on paper indicate that tea is
artificially coloured artificially coloured
Coffee Chicory Shake a small portion in cold water. Coffee will
float while chicory will sink retaining the water
brownish red
Cardamon Oil is removed and On rubbing talcum will stick to the fingers.
pods are coated with On testing, if there is hardly any aromatic
talcum powder flavour, it indicates removal of essential oil
Black pepper Papaya seeds Papaya seeds are shrunken, oval and greyish
brown
Asafoetida Resin or gum 1. Pure asafoetida dissolves in water to form
(scented and a milky white solution
coloured) 2. Pure asafoetida burns with bright flame on be¬
ing ignited

Carraway seeds Grass seeds Grass seeds are smaller than carraway and they
have no smell and taste

49
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY
(Table 9. concluded)

1 2 3

Cinnamon Wood bark It is far harder than cinnamon and may not have
aroma and smell of cinnamon
Cloves Oil may be removed It so, cloves appear shrunken, Nag Kesar will not
give the taste of cloves
Cumin seeds May contain grass If rubbed in hand, fingers will be black
seeds coloured with
charcoal dust
Mustard seeds Argemone seeds Agremone seeds have no round structure, they
are pointed and are more blackish than mustard
seeds
Chilli powder Saw-dust and red Sprinkle on the surface of water. Saw-dust floats.
colour Added colour will colour the water
Saffron Maize fibres dried 1. Genuine saffron is tough, will not break easily
coloured and scented like that of artificial saffron
2. Saffron dissolves easily in water giving aroma
Turmeric 1. Metanil yellow When concentrated HCI is added to solution of
turmeric powder, it turns magenta if metanil yel¬
low is present.
2. Starch Add iodine solution to turmeric solution, it will turn
violet if starch is present
Coriander Horse dung powder Soak in water. Horse dung will float which can be
easily detected
Betel nuts Saw-dust Sprinkle in water, the wood shavings will float and
the added colour will come off in water
Pan masala Saccharin Saccharin is bitter in taste

the infant below 12 months; clear-cut instructions on packing and labelling

of food are also given in the Rules. Details for use of special declarations
such as “unsuitable for babies” are also given. Labels should not contain
false or misleading statements and also words implying recommendations
by medical profession.

QUALITY ENFORCEMENT

Broadly the quality enforcement under the PFA Act can be categorized un¬
der three heads, viz. enforcement, analysis and prosecution.
The food inspectors have been empowered under the PFA Act and Rules
for all the field activities such as lifting of samples from the market, inspec¬
tion of shops, seizing of food articles etc. Food (Health) Authority and Local
(Health) Authority are the officers responsible for looking after the field and
laboratory activities.
The role of the state-level laboratories are very important as the unbi¬
ased implementation of the Act depends on the report of the laboratory. In
case of appeal against the report, reanalysis is done at one of the central
food laboratories. The laboratories are well equipped and the analysts are
qualified and well trained.

50
 FOOD ADULTERATION, FOOD STANDARDS AND LABELLING

After a sample is declared to have been adulterated or misbranded,

prosecution for the offence under this Act is initiated by the authorized
authority and the case is filed in a competant court. After hearing the argu¬
ments of the vendor and Government Prosecutor an appropriate action is
recommended by the judge.
The government has the powers to prohibit the import of any food arti¬
cle or sale of any food article in the interest of consumers health under the
PFA Act and Rules. Packing material should not cause any health hazard to
the consumer or does not contaminate the food. Package containing food
must comply with declaration as prescribed under the PFA Act and Rules
for the knowledge of the consumer. A special reference is made in case of
infant food wherein the approval of the Central Government is necessary for
the purpose of manufacturing sale and storage and for approval of its label.
It has been experienced that publicity in regard to common adultera¬
tion in food, the clause of misbranding and other relevent information in¬
cluding penalty and punishment clauses, have been found very fruitful and
have given positive results. From such publicity not only the individual con¬
sumer becomes aware of adulteration in food articles but also it is beneficial
to the manufacturers and traders to know how they can avoid adulteration
due to natural cause and by adopting proper food hygiene and recommended
practices. The Consumer Protection Council set up under the Consumer
Protection Act 1986 is doing a good deal of service in helping the consumers
to get justifiable redressal of their grievances in way of exchange of prod¬
ucts, and obtaining compensation from the trader or manufacturer in case
of supply of adulterated and substandard food article.

Prevention of food adulteration tips to consumer

Despite the advantages of modern technology, illness due to adulter¬
ated/contaminated food is a leading cause of sickness or death. Food-borne
diseases range from acute gastroenteritis to precancerous/ cancer stage.
Consumers are therefore offered tips (Mukherjee, 1992) in ascertaining qual¬
ity of food by quick and simple test for detection of common adulterants in
food.
While shopping following care should be taken:
• Read label before purchasing.
• Purchase food articles from licenced vendors and insist on Bill or
Cash Memo.
• Prefer foods sold in packed containers even at higher cost.
• Prefer foods certified by Government agencies like Agmark, ISI certi¬
fication mark and F.P.O.
• Avoid coloured foods especially sweetmeats or sharbats or ice candy.
• Buy foods from reputed firms.
• Do not buy cut or exposed fruits or vegetables.
• Do not use containers or packages used for insecticide chemicals or
non-edible items.
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

While preparing or serving food following care should be taken:

• Wash hands with soap and water before the start of preparing food
and after every interruption.
• Cover cuts in hand by bandage
• Cut nails short and keep them clean
• Cover head with hair net or band
• Wear clean overcloths
• Keep all kitchen surface meticulously clean
• Wash foodgrains or vegetables, fruits, eggs, fish, meat thoroughly
before cooking or eating or storing in refrigerator
• Avoid contact between raw foods and cooked foods
• Cook food thoroughly at boiling temperature
• Serve cooked hot food immediately
• Store cooked food carefully, preferably below 10°C or above 60°C
• Protect foods from flies, insects, rodents and other animals
• Keep the refrigerator door closed, defrost or clean refrigerator every
week
• Do not consume stored prepared food if having off (rancid) flavour or
smell or food in which froth has set in.
• Use pure and clean water while preparing food.

Baby care is a difficult job and following care should be taken:

• Mothers milk is best for baby
• After 4 months of age start home-made weaning food
• Do not give left-over food to the baby.

FOOD LAWS

Food laws in any country should be considered as a welcome step to en¬

courage the scientific development of the industry. Food laws and the food
control system helps safeguard the interests of the consumer in two re¬
spects. The more important is that of safety: the health hazards that may
arise on account of adulteration, contamination, microbiological deteriora¬
tion, decay and other factors. The other, generally overlooked, is to protect
the pocket of the consumer, to ensure fair trade practices in articles of food.
These laws thus help prevent to a large extent the losses of foodgrains and
other commodities that may occur through unhygienic storage conditions,
handling, transport and so on. Additionally, food laws should look to the
nutritional requirements of country; wherever considered necessary, food
standards for a food product should lay down the minimum nutrients which
are necessary, in a particular area or in the country as a whole. Yet another
important economic angle is that food laws can prevent the dumping of
imported substandard foods, and on the other hand help earn foreign ex¬
change by exporting foods of acceptable quality. Food is an item which could

52
 FOOD ADULTERATION, FOOD STANDARDS AND LABELLING

account for 50% or 60% of the budget of a family, and thus it is all the more
important that the Government should give some protection to the hard-
pressed consumer.
The prevention of Food Adulteration Act gives a very wide definition of
adulteration. It also covers misbranding. Deletion of certain clauses in the
definition of adulteration has sometimes been suggested by the industry,
under the pretext of occasional unnecessary harassment. The Act also gives
powers to the State Governments, besides the Central Government, to ap¬
point Food Inspectors and Public Analysts who are responsible for the im¬
plementation of the law. The Act provides for the establishment of an Advisory
Committee to advise the Central and State Governments on all matters re¬
lating to the administration of the Act, including standards, food details,
pesticide residues, preservatives, methods of sampling and so on. The Act
also regulates the quality of food imports. It gives powers to the consumers
also to draw samples to a limited extent. An important point is that of war¬
ranty. The Act provides that a manufacturer, dealer or wholesaler has to
give a warranty to a vendor while selling any article of a food and any manu¬
facturer who violates this warranty clause is liable to punishment. The Act
provides for penalties and punishments; an amendment in 1976 has also
provided for summary trials for offences under the PFA Act, with enhanced
powers to the judiciary to impose imprisonment for even up to one year. It
gives powers to the judiciary to incriminate the manufacturer if it feels con¬
vinced during the evidence that he is involved in anti-social activity.
The manner of packing, sealing, labelling, etc., prohibition of certain
admixtures, conditions of licensing, use of food additives like colours, pre¬
servatives, emulsifiers and stabilizers, and such other matters have also
been laid down. The limits of maximum tolerances for the pesticide residues
and other contaminants have also been fixed.
As of today the BIS (ISI) has published 11,500 standards, out of which
about 1,200 relate to agriculture and food products, and some 700 relate to
food. The term quality is a composite of the characteristics that differentiate
the end uses of a product, and of their significance in determining the ac¬
ceptability of the product by buyers. Quality does not necessarily mean the
highest quality attainable, but it may be considered as a state of specifica¬
tion which has to be met within given limits.
Quality-control techniques should be applied for complete manufactur¬
ing and marketing enterprises to obtain as efficient an operation as possi¬
ble. Attributes of quality must be classified broadly into two groups, viz.
sensory qualities and keeping qualities. The former includes colour, gloss,
odour, mouth-feel, viscosity, shape and size, taste and flavour; and the latter
include nutritive value, harmless adulterants and toxicity. These attributes
may be evaluated by physical, chemical and sensory methods.
The quality of food in India lies with organizations related to agriculture
and food products, through different orders and acts like the Agriculture

53
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Marketing Products and Grading Act 1973, Prevention of Food Adulteration

Act 1954, Vegetable Oils Control Order 1947, Fruit Products Order 1955,
Solvent Extracted Deolied Meal Edible Flour 1967, and so on. The Meat
Products Statutory Order 1976, functioning under the Directorate of Mar¬
keting and Inspection (Ministry of Agriculture), enables control of quality in
production of raw and processed meat. There is also the Export Products
Control Order.
How these standards are formulated? If there is a proposal to prepare a
standard, it is first examined by a Technical Committee consisting of mem¬
bers, from Government, different organizations, consumers, railways, de¬
fence, various laboratories, all experts in the particular discipline. They first
screen and examine whether it is possible to draft the standard, then they
circulate this to all members inside and outside India, receive technical
comments, review, examine and finalize the standard and refer it to the
Divisional Council. It is printed and notified to ensure wide publicity of the
formulated standard.
Standards are constantly being changed, revised, reaffirmed, withdrawn
or amendments issued as and when needed based on the advancement of
science and technology. The standards of the raw materials, the quality of
food product in terms of minimum testing, and so on are all mentioned in
standard specifications; even how to reject a sample is described in the
standards.
A large number of chemicals are used in the manufacture of food prod¬
ucts to maintain nutritional qualities, to enhance keeping qualities and sta¬
bility to make the food attractive to the consumer, and to facilitate processing
and treatment. Before a chemical is permitted to be added, under PFA rules
it is always ensured that the substance is free of toxic effects and is em¬
ployed in proper doses. It is also essential that chemicals to be used if the
food industry should be of food-grade purity.
For proper control of processed foods, it is compulsory that food colours
should be certified under the BIS certification and marking scheme. For
hygienic qualities, the consumer does not have adequate knowledge to de¬
termine the quality of food that he purchases, unless the factory concerned
is governed by a strict code of hygiene with respect to layout, plant and
personnel; otherwise the quality of food produced cannot be considered safe,
however nutritious it may be. Keeping this in view, the BIS has prepared
standard codes for sanitary conditions for food-processing units, bakery
units, ice-cream manufacturers, fruit and vegetable canning units, and so
on.
Standards have also been published on the determination and detec¬
tion of salmonella, coliform and bacteria, on plate count and yeast and
mould count, and on food-borne diseases.

54
 FOOD ADULTERATION, FOOD STANDARDS AND LABELLING

FOOD STANDARDS

Food Standards are dynamic instruments which have to keep pace with the
developments being made by both industry and technology in developing a
final product.
With the changing socio-economic trend, there has been an apparent
shift in the food habits resulting the demand for highly processed foods 1
involving sophisticated technology. A wide range of processed foods are now |
being manufactured in the country which include canned jams, curries,
meat, fish,processed breakfast, cereals, papads, soups, noodles, potato wafers j
of different varieties, protein textured foods, frozen pizzas etc. (FTirnanandam ,
and Shashi, 1978).
Standardization and quality control of these processed foods for both
domestic consumption and exports is essential from the view of safety, hy- |
giene, nutrition, keeping quality and other aspects (Fig. 6); with the devel¬
opment of food industries, standardization too has been keeping pace. In
fact, at times, to promote and guide the manufacturers of food item, stand¬
ardization has proceeded the development process (Sharma, 1995).

Efforts to regulate the food quality are being made on in the country
right from 1899, when some provinces had made Rules for this purpose.
The Central Food Advisory Board established in 1937 and the Food Adul¬
teration Committee set up in 1943 after reviewing the subject suggested for
central legislation for bringing out uniformity in food quality laws and making

55
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

it mandatory in the country. This resulted in enactment of Prevention of

Food Adulteration Act, 1954.
Government of India had enacted the Agricultural Produce Grading and
Marketing Act in 1937 for regulating grade standards for various agricul¬
tural produce. The Bureau of Indian Standards (earlier ISI) had initiated the
work on storage of foodgrains and sugar in 1951. However, the work got a
final form 1956 onward, when the Department of Food and Agriculture started
functioning. Various statutory orders like Fruit Products Order; Solvent
Extracted Oils; Deoiled Meal and Edible Flour Control Order; Vegetable Oil
Products Order; Meat Products Control Order under the Essential Com¬
modities Act, 1954 had been enforced from time to time for controlling the
quality of various food items (Sohrab, 1995).
At global level too, emphasis was given for ensuring the food quality. In
1943, UN Conference on Food and Agriculture which resulted in setting up
of Food and Agriculture Organisation*(FAO) in 1945, suggested early action
to assist in the improvement of standards applied to food and other agricul¬
tural products, including the standardization of the containers and pack¬
ages' and to improve the inspection and enforcement. Later with the joint
efforts of the FAO and WHO, Codex Alimentarius Commission was set up in
1962 for setting of food standards. Emphasis was also laid in the UN-spon¬
sored Conference on Standardization in London in 1946 for formulation of
the standards at global level on various agricultural and food products which
resulted in setting up of a Technical Committee immediately after establish¬
ment of International Organization for Standardization (ISO) in 1947. In the
field of dairy products, International Commission for Uniform Methods of
Sugar Analysis (ICUMSA) had already started the work.
Various food laws implemented in our country to safeguard the food
standards are given in Table 10 (Sohrab, 1995). Food products for which
minimum and maximum limits of ingredients are enlisted below according
to the Bureau of Indian Standards (BIS). The standards in general cover
raw materials permitted, their quality parameters, hygienic conditions un¬
der which the product is manufactured and packaging requirements. The
standards also prescribe, where required, freedom from toxic factors like
aflotoxin in food products.
Foodgrain products: Corn flakes, papad, pasta products, rolled oats etc.
Bakery and confectionary: Bread, biscuits, toffees, chewing and bubble
gum etc.
Protein-rich foods: Protein-rich biscuits, protein-based beverage, vegeta¬
ble protein-based yoghurt etc.
Fishery products: Pomfret, mackarel, sardines, funa, prawns etc.
Meat food products: Mutton, goat meat, canned pork, sausage, ham, egg
powder.
Dairy products: Milk, rasgolla, khoa, channa, burfi, ice-cream, infant foods,
flavoured milk; alcoholic drinks and carbonated beverages: rum, beer, gin,

56
 FOOD ADULTERATION, FOOD STANDARDS AND LABELLING

Table 10. Prevailing food laws, acts and implementing agencies for food standards

Act Order Implementing agency Year of Kind of legislation

introduction

Agricultural produce Directorate of Marketing 1937 Voluntary: Compulsory for

(grading x marking) Act Inspection export only

ISI (Certification Indian Indian Standards Institution 1952 Voluntary

marks Act) ' i

Prevention of Food Ministry of Health 1954 Compulsory for internal trade

Adulteration Act

Fruit Products Order Department of Food, 1955 Compulsory for export /

Ministry of Agriculture and Internal trade
Rural Reconstruction

Export (quality control Export Inspection Council 1963 Compulsory for export only
and inspection) Act

Solvent extracted oil, Directorate of Vanaspathi 1967 Compulsory for export/

deoiled meal and edible Internal trade
flour (control) Order

Meat Products Order Directorate of Marketing 1973 Compulsory for export/

and Inspection Internal trade

whiskies, brandies, vodka, country spirit, table wines, toddy etc.

Fruits and vegetables: Pickles, chutneys, fruit squashes, ketch-up etc.
I i

FOOD STANDARDS

Food standards are of different types. They are market standards, end-user
standards, Health Ministry and other government standards, Indian stand¬
ards and export standards. The different standards take into consideration
intrinsic qualities of foods, nutritional aspects, hygienic values and con¬
sumer appeal. Some standards are voluntary in nature and some are man¬
datory.

Market standards
The market dictates some quality parameters in the foodstuffs mar¬
keted. There can be more than one quality requirement for a particular
commodity. The economic status and quality consciousness of the consumer
influences the market standards and they are of voluntary nature. Exam¬
ples are different grades of fruits, vegetables, rice with more or less brokens,
pulses etc.

57
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

End-user standards
End-users are industries and they require special quality factors in the
foods they purchase. Wheat miller requires wheat with high milling yield. A
baker requires a wheat flour with high percentage of gluten of good strength
to obtain a good loaf of bread. A biscuit manufacturer prefers a wheat flour
with lower gluten content. Similarly, fruit-processing industry will require
certain specific qualities in the fruits like colour, flavour when they are
purchased.

Health Ministry standards

These standards are mandatory in nature and are prescribed to ensure
minimum quality in the foods marketed. They are promulgated under the
Prevention of Food Adulteration Act 1954 and the Rules framed in 1955 and
later amended. The Rules cover many food items, viz. beverages, starchy
foods, spices and condiments, sweetening agents, edible fats, milk and milk
products, common salt, fruit products, edible oils, cereal products, vanaspati,
vinegar, sweets and confectionary, food colours, limits for preservatives,
antioxidants, emulsifiable and stabilizing agents, flavouring agents, pesti¬
cide residues.
Quality denotes the degree of excellence of a product. It is indicated in
terms of grades, standards and specifications. These are laid down by a
competent authority in the country. It is an important consideration in mar¬
keting of a product. Consumers have concern about the safety, nutritional
quality, aesthetic value, convenience of use and also cost of foods which
they buy. They have a right to know what is in a processed product and that
it is safe to consume. The consumers are unaware of deleterious effects of
damages in a food article which can easily be masked by modern methods of
processing. To safeguard health of the people from ill-effects posed by various
means of adulteration, it is necessary to exercise a check and control over
the quality of food meant for human consumption. An established system of
quality-control assures uniformity in standards and thereby ensures that
each foodstuff is what it possess to be and what its label declares, if there is
one.

QUALITY AND ITS DOWN GRADATION

Quality of an agricultural commodity can be divided into 2 categories, viz.

intrinsic quality and acquired quality.
The intrinsic quality is a genetic factor. It is divided into 4 categories,
viz. (i) biochemical, (zz) physical, (iii) processing and (iv) storability character¬
istics. The bio-chemical characteristics are its content of protein, fat, fibre,
vitamins, minerals, carbohydrates and enzymes. Even anti-nutrition factors
also come under this category. The physical characteristics are colour, tex¬
ture, size, shape, aroma, and weight. The processing characteristics are

58
 FOOD ADULTERATION, FOOD STANDARDS AND LABELLING

milling yield in case of paddy, wheat and pulses; cooking quality in case of
rice; yield of juices or pulp in case of fruits. Storability of agricultural prod¬
ucts differ from one variety to another. For example, there are differences in
storability of different species of yam.
Acquired characteristics are those acquired during pre- and post¬
harvest conditions and practices. In case of foodgrains there can be (a)
discolouration; (b) infection due to field fungi, e.g. ergot, smut, bunt; (c)
sprouting; (d) admixture with weed seeds, other varieties of foodgrains and
other foodgrains; and (e) contamination with pesticide residues. In case of
fruits and vegetables damages occur during harvesting and field handling,
post-harvest handling, packaging, storage and marketing. At all these stages
quality is affected and down graded. Damages due to mould occur due to
injuries on the product.
Processing technique and conditions also affect the quality of end-prod¬
uct. Milling of paddy in hullers causes to more of broken grain thus reducing
the quality. Metallic implements and machinery parts used in processing
agricultural products cause contamination of heavy metals like lead, arsenic,
zinc and cadmium.
Environmental pollution also has contributed to contamination. Standing
crops along the national highways, when harvested were found to contain
appreciable amounts of lead, obviously from lead tetra ethyl of the automobile
smoke.
Improper storage conditions like storing grain, oilseeds, oil cakes and
feeds with high moisture result in mould damage and probable contamination
with mycotoxins, the famous one being aflatoxin. In canned vegetables, e.g.
peas, certain moulds are responsible for the toxin botulinum.
To protect the vegetable and fruit crops in the field and foodgrains in
storage pesticides are used and sometimes they can be toxic also. Water in
milk, sucrose in honey, starch in milk products, cheaper oils in expensive
vegetable oils, hydrogenated oils in butter oil, dyes in chilli powder, date or
tamarind seed powder in coffee, colouring of turmeric with metanil yellow or
addition of lead chromate and small stones in rice are examples of intentional
adulteration.
In case of spices, the whole spice is subjected to extraction of essential
aromatic components and the residual spices are sold. This is a down-graded
product. Cardomom and cloves are examples of this category.
In case of fruit juices, and allied beverages, minimum percentage of
fruit juice is not present. Similar is the case with sauce and ketchup of
tomatoes. These are in addition to quality down grading due to incorrect
processing techniques.

QUALITY CENTRES

There are various national and international agencies engaged in quality-

59
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

control work either by way of formulating policies, framing standards, lay¬

ing down standard methodology or implementing schemes for its proper
enforcement. At the international level, the WHO and FAO of the United
Nations are the concerned agencies dealing with this subject.
For ensuring safety and health of consumers, the Government of India
has enacted a few Acts and detailed Rules have been framed. They are (z)
agricultural produce (Grading and Marketing) Act 1937, (z'z) Prevention of
Food Adulteration Act 1954 (PFA), (in) Fruit Products Order 1955, (iv) Bu¬
reau of Indian Standards Act 1986 and (y) Export (Quality Control and In¬
spection) Act 1963. In addition, specifications for purchase of foodgrains
are framed by the Department of Food for their use. Defence Ministry pre¬
pares specifications known as Army Corps Specifications, for their purchases
of foodgrains and pulses.

PREVENTION OF FOOD ADULTERATION ACT

The objectives of the PFA Act is to make provisions for the prevention of
adulteration of food entering into the market. The Act empowers the govern¬
ment agencies to prevent this evil and safeguard the consumers. The imple¬
mentation of the Act/Rules is done by the State Governments and Union
Territories through food inspectors. The Central Committee for Food Stand¬
ards advises the government on the implementation of the provisions of the
Act/Rules. The provisions made under PFA are mandatory and it is the
responsibility of the manufacturer or wholesaler or vendor etc. to abide by
the standards of various food commodities. Broadly the control of the qual¬
ity can be categorized under three heads, viz. (z) enforcement, (z'z) analysis
and (izi) prosecution.
The PFA standards are the minimum standards of purity and are based
on the agricultural and manufacturing practices followed in the country.
Samples which do not conform to the specifications are considered unfit for
human consumption from hygienic angle. The Act deals with preservatives,
poisonous metals, naturally occurring toxic substances, anti-oxidants, emul¬
sifying and stabilizing agents, flavouring agents, colouring matter and other
food additives, insecticides and pesticides, solvent extracted oils and edible
flours, non-alcoholic beverages, starchy foods, spices and condiments and
their mixes, honey, jaggery, saccharin, coffee, tea, milk and milk products,
fruit products, edible oils, cereals, baked products, sweets and confection¬
aries, and a range of similar products. The Act deals with definitions and
standards of quality.
To enforce the provisions in the Act and Rules, the government has set
up four central food laboratories and a number of laboratories at State and
Union Territories level where analysis of seized articles of food is done by
trained analysts. These laboratories are well equipped with modern instru¬
ments.

60
 FOOD ADULTERATION, FOOD STANDARDS AND LABELLING

AGMARK
The Agricultural Produce (Grading and Marketing) Act was enacted by
the Government of India in 1937 with the basic aim of protecting the con¬
sumer, and at the same time ensuring the producer a just return for his
produce. The Directorate of Marketing and Inspection established under
this Act, has set up a number of analytical laboratories and commodity¬
testing centres for enforcing the quality-control programme on agricultural
commodities.The quality-control testing is done by primary grading labora¬
tories which are under private, co-operative and state sector and they carry
out testing/and grading at producers level. Their work is checked and su¬
pervised by the Regional Agmark Laboratories established at 21 centres.
Thesedaboratories are under technical control of the Central Agmark Labo¬
ratory at Nagpur. It is an appellate and apex laboratory of the Directorate.
The network of Agmark Laboratories test about 140 agricultural and
horticultural commodities. The schedule consists of fruits, vegetables, eggs,
dairy produce, tobacco, coffee, processed cereals and also lac, sunhemp,
myrobalans, wool and goat hair, bristles, resin and turpentine, essential
oils, spices, honey, tapioca chips and flour, oil cakes etc.
The Directorate authorizes marking of packings of agricultural prod¬
ucts (bag, bottle, can, tin etc.) with their logo and grade designation mark
on payment of specified fees. This implies that the product is duly tested
and found in conformity with the Directorate Standards. It is known as
AGMARK Standards. There are penalties for unauthorized marking with
grade designation mark, counterfeiting grade designation mark and for sell¬
ing mis-graded articles.
The AGMARK Standards are quality standards, depending on the degree
of excellence of the produce. They are more rigid than the PFA Standards.
AGMARK Standards are voluntary in nature in general and the producer or
manufacturer get registered with the Directorate with a view to boost up his
sales with AGMARK registration mark on his product. The government en¬
forces compulsory grading of certain agricultural products particularly for
export purposes. AGMARK label/replica on a container helps the consumer
to be sure of what he purchases. There is a consumer protection cover when
one buys AGMARK products. It means a defective product will be replaced
free of cost or money refunded.

Fruit products order

The Government of India promulgated Fruit Products Order (1955) to
exercise the powers conferred by the Essential Commodities Act (1955). No
person can carry on the business of manufacturing except under and in
accordance with the terms of an effective licence granted to him under this
order. A fee is levied on the manufacturer, depending on the scale of pro¬
duction. The manufacturer has to manufacture fruit products in continuity
with the sanitary requirements and the appropriate standards of quality

61
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

and composition specified in the Schedule to this Order. The manufacturer

has to comply with the specified requirements in regard to the packing,
marking and labelling of containers of fruit products. Each container should
display licence number of the special identification mark, code number in¬
dicating the lot or the date of manufacture of such fruit product. The labels
should not contain any statement, claim, design or device which is false or
misleading concerning the contents in the container.
The licencing officer can inspect the manufacturing unit, collect samples
intended for sale and get them analysed at a laboratory authorized for this
purpose. Penalties such as fine, closure of the unit and even imprisonment
will be levied if malafide intentions and neglect are proved in the manufacture
and complying with the FPO.
The FPO covers all types of fruit products such as juices, pulp concen¬
trates, squashes, nectar, aerated water containing fruit juices, bottled and
canned fruits and vegetables, jams, jellies, fruit cheese, preserves, chutneys,
soups, ketchup, paste, dehydrated vegetables and dehydrated onion. In
addition to specifications for various products, limits for poisonous metals,
list of permitted and harmless food colours, limits for permitted preservatives
and other additives are given in the schedules.

FAQ (Fair average quality) specifications for foodgrains

The Food Department of Government of India procure about 20-25 mil¬
lion tonnes of both wheat and rice every year for distribution through a
network of fair price shops in the country. They prescribe specifications for
wheat, paddy, and also coarse grains every year. The procuring agencies
apply these specifications while accepting the stocks. These specifications
confirm to the mandatory standards of PFA and are always more rigid. How¬
ever, they take into account the agricultural practices followed, climatic
conditions at the time of harvest and also the requirements of middle and
lower income groups with reference to their purchasing power. The specifi¬
cations are known as Fair Average Quality (FAQ) specifications. The pro¬
curement is done through Food Corporation of India, State Governments
and Co-operative Organizations.

Bureau of Indian Standards

The Bureau of Indian Standards, a government body, also prescribes
quality standards for agricultural products and processed foods such as
milled wheat, maize, barley, pulse products, corn flakes, macaroni, spaghetii,
biscuits, bread, etc. The division of Agricultural and Food Products constitutes
different committees consisting of representatives of concerned government
departments, scientific institutions, manufacturers, traders etc., who prepare
quality standards for mainly processed food items. They prepare standards
for methods of analysis also. It is obligatory to adopt this methods of analysis
wherever they exist by all the laboratories in the country. As in case of

62
 FOOD ADULTERATION, FOOD STANDARDS AND LABELLING

AGMARK, ISI mark can be used by the manufacturers after registering with
them and complying with their stipulations regarding inspection and testing
of their products by them. The BIS Standards are quality standards and
more rigid than PFA Standards.

Consumer protection act

The Consumer Protection Act 1986 and the Central Consumer Protection
Rules 1987 were enacted by the Government of India to provide better pro¬
tection of the consumers and for that purpose to make provision for the
establishment of Consumer Councils and other authorities for the settlement
of consumer disputes and to promote and protect the rights of consumers.
This Act and Rules cover the right to be protected against marketing of
goods hazardous to life and property, right to be informed about the quality,
potency, purity, standard and price of goods. It protects consumer against
unfair trade practices. Consumer Forums at district level and State level
and National level Consumer Dispute Redressal Commissions are set up to
hear the complaints of the consumers. Consumer councils at various levels
have also been established to advise the consumers for their rights.

Export Inspection Council

Export Inspection Council has been set up under the Export Inspection
Act to have a check on quality of food articles exported.

Other quality control legislations

Under the Essential Commodities Act of 1954, in addition to the Fruit
Products Order 1955, Vegetable Oils Product Control Order 1947 and Meat
Product Control Order 1973 were formulated to regulate manufacture, com¬
merce and distribution of vegetable oils and their products and meat products
respectively. Specifications of food articles formulated under these orders
are in line with the standards laid down under the PFA.

Rule: A-18.06 Food grains

(z) Foreign matter: inorganic matter 1% (in paddy 3%), organic matter
3%; (zz) Damaged grains 5% by weight; (zz'z) insect-damaged grains (by count)
not more than 10%, uric acid content as a result of insect damage not more
than 10 mg/100 g; (iv) rodent hair and excreta not to exceed 5 pieces/kg
sample; and (r) moisture not exceeding 16%.

Rule A-07.03 Honey

It shall not contain (a) more than 25% of moisture, (b) 0.5% ash and
(c) 5% sucrose. The minimum reducing sugar content shall be 65%. Fruc¬
tose glucose ratio shall not be less than 0.9% by weight. It shall not contain
any artificial sweetner.
The Ministry of Food and Civil Supplies lays down specifications for
paddy, rice, wheat, sorghum and other millets yearly. The specifications

63
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

and relaxations if any given later, take into consideration the fair average
quality requirement of consumers and the conditions of production. The
grain-procuring agencies, viz. Food Corporation of India and State Govern¬
ments, follow the specifications in procuring foodgrains for distribution
through the Public Distribution System. A total of 20-25 million tonnes
foodgrains are purchased with these specifications.
The Agricultural Marketing Directorate has also their specifications for
different food commodities. These are called Agmark specifications.
The Army Purchase Organization has their own specifications for differ¬
ent food commodities and they apply these specifications for their purchases.
Indian standards are laid down by the Bureau of Indian Standards
(BIS). These standards are arrived at by experts in the industry, research
and development organizations and by those in marketing and concerned
ministry. The standards are aimed at providing a good-quality product to
the purchase of the product for the price he pays. These standards are not
mandatory but are to be adopted on voluntary basis. The BIS registers the
industry if it intends to make use of their standards and allows them to
print BIS mark on the packing. The Bureau gets the product inspected
during manufacturing process to ensure that the concerned industry pro¬
duces the product as per the specifications. The BIS mark on the packing
indicates good quality of the product. The Indian standards are available for
a variety of industrial products including electronic goods, machinery, stor¬
age structures, pesticides and their formulations and food products.

FOOD LABELLING

Food labelling is an essential component in all food-processing industries.

The purpose is to tell the consumers, in a correct manner, about the content
of the foods inside the package or container. The consumers want to know
what a package contains to be sure that they are not paying for an unknown
quality and quantity of the food in the package. It leads to the necessity of
enumerating on the label the ingredients, net contents and other essential
points about the food in the package. It is also equally important that the
declarations and claims made on the label are true and reflect the product
packed (Sidappa and Tandon, 1959).
The standard has been issued in three parts and thus providing impor¬
tant information about the product to the consumer.

Parti
Covers general guidance on labelling.

Part II
Covers claims and lays down the conditions under which claims includ¬
ing nutritional, dietetics and medical claims may be made. It also lays down

64
 FOOD ADULTERATION, FOOD STANDARDS AND LABELLING

that marketing, insubstantiated, meaningless claims, or those which arouse

fear in consumers in or give rise to doubts about safety of similar foods are
prohibited.

Part III
Covers guidelines on labelling with respect to nutritional information.
The standard lays down that any nutrient added to food or any nutritional
claim for information should be declared on the label. The manner in which
the information is declared is also given on the label as also the amounts of
addition under which declaration is compulsory or optional for each nutrient.
Nutritional labelling has come in conjuction with food labelling in re¬
cent times to give more information to the consumer. It helps consumer to
buy the foods he exactly needs with specific nutrients. Nutritional labelling
will upgrade the nutritional quality of the food supply because the food
industry has increased responsibility to determine what nutrients are actu¬
ally contained in the food they are selling and to reveal the facts plainly. The
importance of nutritional labelling can be observed in baby foods, conven¬
ient foods, therapeutic foods, geriatric foods etc.
Labelling of marketed food products is necessary to increase the sales.
Apart from attractive design, name and colours, the label has to indicate
some details of the product for the benefit of customers. This is made ob¬
ligatory by Fruit Products Order in case of all processed fruit products mar¬
keted. As explained earlier there are Agmark Standards and Indian Standards
also which are of voluntary nature. The respective organization permits the
use of Agmark or BIS mark on the labels when the manufacturer prepares
the product according to the specifications laid down by the organizations.
When the consumer notices the FPO mark, ISI mark or Agmark, he is sure
that the product is of standard quality.
Typical examples of labels are given here.

FPO labelling
Orange squash. Net contents 700 ml, Ingredients: sugar, water, orange
juice, citric acid, orange oil, colour and preservatives. It contains permissible
colours, added flavours and permitted Class-II preservatives.
Manufactured : March 90
Batch No. : 15
Maximum retail price :
Local taxes extra :
FPO mark and number :
Manufacturer’s name :

ISI mark
Britannia Good day butter
Britannia Industries Limited
5/1 A Hungerford Street, Calcutta 700 017

65
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Contains wheat flour, sugar, edible fats, butter, milk and milk prod¬
ucts, leavening agents, salt, dough conditioner, permitted emulsifiers and
antioxidants.

Biscuits
Net weight : 100 g
Biscuit design registered
under No :
Max. retail price : Rs (inclusive of all taxes)
IS : 1011
Packed ; 8/90 (ISI)

FPO marking
Maggi
Tomato Ketchup : Rs

Manufactured by : Food Specialities Ltd.,M.S.A.

Connaught Circus, New Delhi \ 10 001
Net contents : 400 g
Maximum price Rs (inclusive of local taxes)
Mfd. : March ‘89
Batch :

Ingredients: Water, tomato paste, sugar, salt, emulsifying and stabilis

ing agents, acetic acid, spices, permitted class-II preservatives.

Agmark marking
Under Licence of Agmark marking:
A.S. Brand
AGMARK AGMARK Label: Govt of India
Husked No:
Gingelly (Til) Oil Sesame Oil
Ambatti Subbanna & Co. Graded
Samalkot (A.P.) (edible)
Ideal Cooking Medium
Net : 2 kg (when packed)
I.F. No.
Manufactured on
Maximum price : Rs (Local taxes extra)

The above examples show how labelling system on packed goods has
been developed as against no labels on all unpacked items like wheat, rice,
pulses etc. Even in these items also, some wholesale dealers and manufac¬
turers are making consumer packings such as basmati rice, wheat atta
(flour). Consumers especially in urban areas have become quality conscious

66
 FOOD ADULTERATION, FOOD STANDARDS AND LABELLING

and demand quality products. They do not mind paying slightly more money
for a particular item. Therefore the manufacturers with the help of standard
developing agencies, produce quality foods and also advertise through ap¬
propriate labelling.
Fixing safety standards for various non-toxic and toxic contaminants in
agricultural produce is not an easy proposition, especially in case of toxic
contaminants such as heavy metals, mycotoxins, pesticide residues, pro¬
hibited colours, they will be present in microgram levels or even in lower
levels. Various analytic methods so far developed to detect such minute
levels, almost invariably employ costly and sophisticated instruments like
gas liquid chromatography, ultra-violet and infra-red spectrophotometers,
atomic absorption spectrophotometer etc. Again careful selection of the
methods of analysis on the basis of extensive collaborative studies between
various laboratories within the country is a pre-requisite for obtaining reli¬
able data on which national safety standards can be based. False positive or
negative results will be common occurrences otherwise. Therefore qualified
and trained technicians will be necessary to work in the testing laborato¬
ries.
For implementing safety standards or quality standards, infrastructure
has to be established. This consists of field-level inspectors, public analysists
and establishment of regional level laboratories, and an apex or appelant
laboratory for reanalysis in case of appeals against the reports of regional
laboratories. Fool-proof procedures have to be developed from lifting of sample
for prosecution through courts and police. Central Committee for Food Stand¬
ards with members from scientific organization, manufacturers, trade and
government administrative departments have to be active and attend to
development and implementation of safety and quality standards keeping
in view the socio-economic conditions in the country, safety of consumers,
developments made in other countries and recommendations of interna¬
tional organizations.
Voluntarily quality standards will be adopted by the manufacturers of
agro food products, especially when there is competition among themselves
to boost their sales. It has been experienced that publicity with regard to
common adulterants in food, the relevance of registration mark of quality
such as AGMARK, FPO and BIS on the marketed products, have been found
fruitful and have given positive results. From such a publicity not only the
individual consumer gets aware of adulteration in food but also it is benefi¬
cial for the manufacturers and traders to know as to how they can avoid
adulteration due to natural causes or accidents, and how to maintain proper
food hygiene and make appropriate label declaration on a food container.
Consumer Councils, Consumer Forums and Commissions and provisions
made under the PFA Act are helping in implementation of both safety and
quality standards and in protection of consumers against unfair trade prac¬
tices in the country.

67
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

AGRO-CHEMICAL RESIDUES IN FOOD ITEMS

To meet the needs of growing population, we require massive food production

programme and this in turn is impossible without the use of pesticides. But
farmers, in their over-enthusiasm to save crops from pests and diseases,
tend to use more than the recommended doses of pesticides.
The use of pesticides has increased from 430 tonnes in 1954 to 90,000
tonnes in 1999 in India. It is likely to increase further with increasing agri¬
cultural production.
Excessive use of pesticides has led to high residues in foods and their
toxic metabolites in the environment.
Even small quantities of these residues consumed over long periods can
build up to high levels in the body fat.
Long-term effects of consuming pesticide residues varies from minor
health problems to serious health hazards, such as carcinogenecity, re¬
duced life-span and fertility, increased cholesterol, high infant mortlaity
rate, varied metabolic and genetic disorders.

Safe levels
In order to regulate contamination of food with pesticide residues to
safe levels, government has laid down principles for arriving at maximum
residue limits of pesticides in food commodities. This is the level at which no

Table 11. Tolerance limit of common pesticides

Pesticide Food Tolerance limit

(mg/kg)

Aldrin, dieldrin Fruits and vegetables 0.4

Carbaryl Okra, leafy vegetables, potato 10.4
Chlordane Vegetables 0.2
Fruits 0.1
Diazinon Vegetables 0.5
Dichlorvos Vegetables 0.15
Fruits 0.1
Dicofol Fruits and vegetables 5.0
Dimethoate Fruits and vegetables 2.0
Endosulfan Fruits and vegetables 2.0
Fenitrothion Fruits 0.5
Vegetables 0.3
Heptachlor Vegetables 0.05
Inorganic bromide Fruits 30.0
Lindane Fruits and vegetables 3.0
Parathion Fruits and vegetables 0.5
Parathion methyl Fruits and vegetables 0.2
1.0
Phosphamidon Fruits and vegetables 0.2
Pyrethrine Fruits and vegetables 1.0

Source: Srivastava, J. L. 1980

68
 FOOD ADULTERATION, FOOD STANDARDS AND LABELLING

harmful effect on the most susceptible species is ascertained. It is used to

arrive at the level of intake which is considered safe for humans even if they
consumed for their whole lives.
In India under the Prevention of Food Adulteration Act 1954, limits of
tolerance for pesticide residues in food and food commodities have been
prescribed for a limited number of pesticides (Table 11).

Safety periods
Every pesticide has some safety period or waiting period. Safety period
is the number of days to lapse before the pesticide reaches the tolerance
limit.

Dissipation
The food commodity concerned is safe for consumption only after the
lapse of the waiting period; the residues get dissipated by this time. Pesticides
begin to get slowly dissipated after being sprayed. And the environment ■
including soil, water, air, other plants, birds and humans get contaminated
in the process (Fig.7).

AIR
Fall out through Evaporation
rain and drift' Fall out
Vapours Seed treatment
•Spraying' Foodgrains
Vegetable, Fruits
Manufacture
Formulation
Spraying

Dairy
Spraying pest
products
Pest control
Spoilage
Washing

Micro¬ Aquatic animals

organism
Urine and feces

Fig. 7. Pesticide contamination

If the fruits and vegetables are harvested before completion of the wait¬
ing period, it is likely to have higher level of residues.

Effects of processing
Pesticide residues get dissipated over a period of time. However, partial
decontamination is possible through processing.
The extent of removal depends on the nature of the chemical, type of
food, length of contact with food, and environmental conditions.

69
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Peeling and trimming vegetables and fruits before eating reduces the
residues in tomato, grape and mango.
In cauliflower and tomato, storage at room temperature enhances dissi¬
pation compared with storing in refrigerator or deep freeze.
No residues are found in cauliflower when harvested 9 days after spray.
Washing reduces 50-75% residues in cauliflower and cooking reduces al¬
most completely. Washing, soaking in 2% salt solution, cooking in slightly
acid medium like lime juice or tamarind extract removes more than 75%
residue. Soaking of grapes in 2% salt water for 10 min. followed by washing
removes most of the residues. In green leafy vegetables it is difficult to re¬
move the residues with one washing. Two washes are better or result in
complete removal (Table 12).
Table 12. Removal of insecticides by common processing procedure in vegetables

Vegetable/insecticide Washing with 2% salt Washing and

water and cooking for 15 min. steam cooking

Beans
Malathion 60 69
Monocrotophos 42 47
Carbaryl 58 69
Chillies
Monocrotophos 28 30
Quinalphos 22 29
Tomatoes
Carbaryl 67 75
Monocrotophos 31 32
Quinalphos 29 30

Source: Pesticide contamination, Bulletin, Andhra Pradesh Agricultural University, 1987.

Biological effects
Pesticide residues cause acute and long-term toxic effects in humans,
animals, fish and birds.
Even when properly used it can cause ill-effects because of persistence
and tendency of some compounds to concentrate in organisms as they move
up the foodchain (Geervani, 1994).
DDT accumulates in the fat and causes more toxicity in malnourished
population. Pesticides affect the point of contact such as skin and eyes
during spraying operations. People constantly exposed to such sprays of
insecticides have to be careful about health hazards due to direct contact
and inhalation. Sometimes, people exposed to pesticide sprays may not show
any effects immediately. But due to sensitization of body, allergic reaction
can occur and, in such cases, each additional exposure no matter how small,
will cause serious health problems. Immediate effects may be dizziness,
burning eyes and skin rash.
Continuous exposure for longer periods can cause liver or kidney dam-

70
 FOOD ADULTERATION, FOOD STANDARDS AND LABELLING

age or damage to nervous system; it can also cause mutations resulting in

birth defects.
In experimental animals it is seen to cause cancer.
The types of health hazards depends on the nature and property of
pesticide, the amount deposited in the body and the period of exposure.
Sometimes pesticides are contaminated with more toxic compounds
which can cause cancer and can lead to risk of life.
In spite of ban on use of DDT for agricultural production in 1989, it is
being used sometimes out of ignorance and sometimes due to indifference.
Relatively high levels of DDT and its metabolites have been reported in the
body fat of Indian population. While WHO has indicated that maximum safe
limit for DDT to be 0.01 mg/kg body weight/day, newborns consuming
breast milk from mothers exposed to pesticide sprays are consuming 100
mg DDT/day.
Two most common pesticides used for vegetable crops are monocrotophos
and cypermethrin. Monocrotophos toxicity leads reduction in body weight
of experimental rats, reduction in birth weight and higher neonatal deaths
in litters born to rats.
There are enough scientific evidences that, prolonged ingestion of
cypermethrin and monocrotophos can lead to reduction in brain weight,
reduced enzyme activity and other neurotoxic effects.

POINTS FOR ACTION

There is a need of random checking of market samples, to prevent harmful

effects of pesticide residues.
We should have programmes through mass media to educate farmers,
labourers and public on the hazards due to misuse of pesticides. We also
need enforcement of regulation governing the use of pesticides.
We should creat facilities for analysis of food samples at district and
state level for monitoring. All agencies connected with agriculture and food
commodities directly or indirectly should take it, as this is their primary
responsibility to help in safeguarding the health of consumers and public
by giving necessary information on the correct usage of pesticides and on
harmful effects of misuses of pesticides.
It is not enough we produce more food by using pesticides, but we should
see to it that food produced is safe for human consumption.

REFERENCES

APAU. 1987. Pesticides Contamination Bulletin. Andhra Pradesh Agricultural University,

Hyderabad.
APAU. 1989. Pesticides Contamination Bulletin. Andhra Pradesh Agricultural University,
Hyderabad.

71
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Geervani, P. 1994. Practical hints for coping with pesticide residues in food items. Health
Action (January), pp. 17-19.
Purnanandam, T. and Shashi, K.V. 1978. Role of Indian Standards in the quality control of
processed foods. Proceedings of the Seminar on Quality Control of Processed Foods, Asso¬
ciation of Food Scientists and Technologists, India.
Sharma, R.N. 1995. Quest for quality in food sector—Role of standards. Indian Food Industry
14(6): 52-60.
Sidappa, G.S. and Tandon, G.L. 1959. Preservation of Fruits and Vegetables. Indian Council of
Agricultural Research, New Delhi.
Sohrab. 1995. ISO 9000 and Food Industry. Indian Food Industry 14(2): 34-38.
Srivastava, J.L. 1980. Pesticide residues in foodgrains and pest resistance to pesticides. Bul¬
letin of Grain Technology 18(1): 65-74.
Suhasini, V. R. 1994. Findings Adulterants in food items, some do at home tests. Health
Action 7: 9-10.

LEARNER’S EXERCISE

1. Write about PFA act and its rules.

2. Explain simple tests to detect food adulteration in day-to-day life.
3. Give some tips to consumer while selecting a product.
4. Enumerate prevailing food laws, acts and implementing agencies for food standards.
5. What are the various types of food standards?
6. Enumerate the following Agmark, FAO, FAQ, BIS.
7. Write about:
(a) Consumer protection act
(b) Quality control legislations
(c) Agrochemical residues in food-processing industry
(d) Importance of food labelling
(e) Pesticide contamination and health hazards.

72
 Microbes in
foods

F ermentation may be defined as the incomplete oxidation of complex

organic compounds particularly carbohydrates with the help of enzymes
produced by micro-organisms. Natural fermentations have played a vital
role in the preservation of foods from early times. The foods produced by
fermentation are cheese, curd, butter, all alcoholic beverages, pickles, sau¬
erkraut, vinegar, bread, idli, soya sauce, coffee, tea and cocoa. It can be
carried on only by anaerobic or faculatative, heterotropic micro-organisms.
In this method of respiration, the cell absorbs food, which is usually a simple
sugar. A number of bacteria also cause fermentation of carbohydrates, a
few decompose cellulose and others decompose polysaccharides like
starch, dextrin and insulin.
A large number of species breakdown disaccharides like lactose (milk
sugar), maltose (malt sugar) and sucrose (cane sugar). Industrial microbiol¬
ogy deals with all forms of microbiology which have an economic aspect.
The ability of micro-organisms to convert inexpensive raw materials or
substrates, to economically valuable organic compounds obviously is of con¬
siderable concern to the industrial microbiologist. Also of great interest is
the economic value of the microbial cells themselves, and of the intracellular
and extracellular enzymes elaborated by the organisms. The activities of
these enzymes are important to the success of an industrial fermentation
process, because they are associated with the micro-organisms ability to
attack, degrade and utilize components of the medium, and to accumulate
fermentation products. Enzymes from microbes can be economic products,
e.g. microbially produced invertases, amylases, and proteases. On the other
hand sometimes, microbial enzymes also mediate the deterioration.
Fermented products may be components of the microbial cells, the cells
themselves, intracellular or extracellular enzymes, or chemicals which are
produced or altered by the cells. Various commercially important products
of microbial activity are given here.
• Beverages: Wine, beer, and distilled products
• Foods: Cheeses, fermented milks, pickles, sauerkraut, soya sauce,
yeast, bread, vinegar, mushrooms and acidulants such as citric acid
• Flavouring agents: monosodium glutamate and nucleotides
• Flavouring organic acids: Lactic, acetic, citric, gluconic, butyric,
fumaric, itaconic, kojic, etc.
• Glycerol

73
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

• Amino acids: L-glutamic acid and L-lysine

• Steroids
• Wide range of compounds used as chemical intermediates for further
chemical synthesis of economically valuable products.
• Baker’s yeast
• Food and feed yeast
• Legume inoculant
• Bacterial insecticides: for example, Bacillus thuringiensis
• Vitamin and other growth stimulants: B12, riboflavin, vitamin A and
gibberellins
• Enzymes: amylases, proteases, pectinases, invertase etc.
• Fats
In food preservation by fermentation in contrast, multiplication of micro¬
organisms and their metabolic activities are encouraged. However, the micro¬
organisms that are encouraged to grow and multiply are the selected groups,
whose metabolic products help food preservation.
Natural fermentation has played a vital role in the preservation of foods
from early times. Fruit juices exposed to air undergoes natural fermentation
and acquired an alcoholic flavour. This change is used as means of preser¬
vation of perishable foods. This change in the taste and texture to the fer¬
mented foods is desirable.
The preservative effect of fermentation is caused by chemicals excreted
by the micro-organisms. The principal chemicals involved are acids (espe¬
cially lactic acid) and alcohol. These inhibit growth of common pathogenic
organisms in foods. For example, the toxin-producing Clostridium botulinum
cannot grow at pH below 4.6. Especially fruit products are preserved in this
way.

FERMENTED BEVERAGES

Fermented beverages have been known to. mankind from times immemo¬
rial. Grape wine is the most important among these wines made from fruits
and are named after the particular fruit employed. Thus apple cider from
apples, percy from pears and orange wine from oranges are available. Starch
and sugar also are fermented to get special types of liquors (Giridhari Lai
etal, 1967).

Preparation of grape wine

Grapes intended for wine making are sorted to remove mouldy bunches
and then they are crushed. In white grapes, the crushed mass is pressed
directly in basket-type presses. Generally the yield of juice is 60-70%.
Grape wines are of dry and sweet types. In the dry wine, there is prac¬
tically very little or no sugar. In the sweet wine either fermentation is arrested
to retain some of the original sugar or extra sugar or fresh grape juice is

74
 MICROBES IN FOODS

added, to the fermented juice. The alcohol content of these wines ranges *
from 7 to 20%.
To ferment, the juice which is popularly known as 'must’ in fermenta¬
tion industry, is a culture of pure wine yeast like Saccharomyces ellipsoideus
is added as a starter. Sulphurdioxide is added to the ‘must’® 50-70 ppm to
check the action of wild yeast and bacteria which are undesirable in alco¬
holic fermentation. The temperature should be maintained between 27°C
and 29°C. Fermentation virtually ceases at about 38°C.
When fermentation is complete, the clear wine is syphoned, filled com¬
pletely and sealed air-tight to exclude all air. In course of time the wine
matures. During this maturing or ageing process, which takes 6-12 months,
the wine losses its raw and harsh flavour and mellows down considerably
acquiring a smooth flavour and aroma. Barrels of oak wood are generally
preferred for maturing, as they impart a fine bouquet to the wine.
During the maturation process, there is natural clarification of the wine.
Filter aids, white of egg etc., can also be employed for clarification.
The volatile acidity of wine, which is mainly due to acetic acid, should
be low. It is desirable to pasteurize the wine to destroy spoilage organisms
and coagulate the colloidal materials which cause cloudiness in the wine.
Wines are generally pasteurized for 1-2 min. at 82-88°C and are kept in
bottles. The bottles are closed with bark corks of good quality. Alcohol con¬
tent of wines ranges 6-9% by weight or 8-13% by volume.
There are various kinds of wines, some countries specialize in the manu¬
facture of typical wines, which have made the country famous for wines.
They are Champagne, Port, Muscat, Toray, Sherry, cider, perry etc. The
organisms responsible for wine spoilage are Acetobactor, Lactobcillus and
Leuconostoc.

Malt beverages
Beer and ale, usually malted beverages contain malt (prepared from
barley); hops (dried flowers of the hop plant), yeasts, water and malt ad¬
juncts (starch or sugar). Starch can be obtained from corn and its products,
rice, wheat, barley, sorghum grain, soybean, cassava, potato etc., and sweet
adjuncts are sugar and syrup. Germinated grains are ground with water at
38-53°C, steam cooked starchy malted adjuncts in water, saccharification
(production of sugar from the starch) takes place and temperature increases
to 75°C, which inactivates the enzymes. Insoluble matter settles down (filter).
Hops are added to the clear liquid (wort). The wort is boiled with hops for 2^2
hr (to inactivate enzymes, coagulation of protein, caramalization of sugars).
Filter (hop solids and proteins precipitate) and the wort is fermented with
Saccharomyces camisbergensis (pitching).
Beer; The process of beer is outlined briefly as an example of the brewing
process.
Malting: In the preparation of malt, barley grains are soaked or steeped

75
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

at 10-15°C, germinated at 16-25°C for 5 to 7 days and dried and powdered.

The malted powder is source of amylases and proteinases.
Mashing: The purpose of mashing is to make soluble as much as possible
of the valuable proteins of the malt and malt adjuncts especially to cause
hydrolysis of starches and other polysaccharides and of proteins and products
of their hydrolysis.
During fermentation the yeast converts sugar to alcohol and C02, glycerol
and acetic acid, protein and fat derivatives produce higher alcohols and
acids and organic acids and alcohols to produce aromatic esters.
Ageing or maturing: The young or ‘green’ beer is stored in vats at about
0°C for several weeks to several months. During ageing, precipitation of
undesirable protein, yeast, resins etc. takes place. The beer becomes clear
and mellowed or matured. Esters produces taste and aroma.
Finishing: After ageing the beer is carbonated (C02 content of about
0.45 to 0.52%), cooled, clarified or filtered. The finished product is packed
in bottles, cans or barrels. Alcohol content is about 3.8% by weight.
The defects and diseases seen in beer production are turbidity (due to
unstable protein, tannins, starches and raisins), off-flavours and poor physi¬
cal characteristics.
The bacteria causing beer diseases are mostly from the general
Pediacoccus, Lactobacillus, Flavobacterium and Acetobactor.

VINEGAR

Vinegar is the oldest known fermentation product derived from French

Vinaigre’ means sour wine. It contains about 5% of acetic acid in water,
varying amounts of fixed fruit acids, colouring matter, salts, and a few other
fermentation products which impart a characteristic flavour and aroma to
the product. Vinegar is labelled according to the material used in its manufac¬
ture. For example, vinegar made from malt is called malt vinegar and the
one made from apple juice is known as cider vinegar and so on.

Quality standards
Vinegar is a liquid derived from various materials, containing sugars
and starch, by alcoholic and subsequent acetic fermentation.
1. It should contain at least 4% acetic acid/100 ml and a corresponding
quantity of the mineral salts of the material from which it is made.
2. It should not contain arsenic in amounts exceeding 0.0143 mg/100
ml, nor any mineral acid, lead, copper or colouring matter except caramel.

Grain strength
The percentage of acetic acid present in the vinegar is represented in
terms of grain strength. The percentage of a vinegar is ten times the per-

76
 MICROBES IN FOODS

centage of acetic acid present in it. Vinegar is made from various fruits and
also from sugar.
• Vinegar made from apple juice by fermentation is called apple cider
vinegar or simply cider vinegar.
• Vinegar made from grapes by acetic acid fermentation is called wine
vinegar or grape vinegar.
• Fruit juices and sugar solutions of low concentration ferment of their
own accord owing to wild yeasts normally present in fruits.

Preparation of vinegars
Depending on the type of vinegar, the juice is extracted from the fruits
or sugar and clarified before fermentation. To get a vinegar of good quality,
it is therefore essential to destroy all the naturally occurring yeasts and
other micro-organisms, by pasteurization and then to inoculate the sterile
juice thus obtained with pure yeast.
Alcoholic fermentations occurs in two stages, i.e. the first is the prelimi¬
nary or vigorous fermentation stage and the second is the slow fermentation
stage. During the first 3-6 days most of the sugar is converted into alcohol
and carbondioxide. This fermentation is rapid.
The secondary fermentation is much slower and usually takes 2 or 3
weeks. During this fermentation, contamination with vinegar or lactic acid
bacteria may take place. Under favourable conditions fermentation is com¬
plete in 72-96 hr. During fermentation, gas bubbles are constantly produced
and when fermentation is complete, their evolution ceases.
Ageing: After completing the fermentation, to improve its flavour, vin¬
egar is kept in plain oak barrels for about six months. During this period, its
harsh flavour changes to a more pleasant aroma and bouquet. Acetic acid
may react with alcohol to form ethyl acetate which has a fruit flavour.
Clarification: Before bottling, vinegar must be made sparkling clear. During
ageing most of the suspended material settles down leaving a clean major
portion of the liquid clear. This clean liquid can be syphoned out for further
clarification. This can be accomplished either by using finnings such as
Spanish clay, bentonite, insinglass, casein, gelatin, or by filtering through
pulp filters or aluminium plate and frame presses. If finnings are used the
vinegar has to be stored for about a month to render it clear.
Pasteurization: The vinegar, after ageing and clarification, is pasteurized
to check any spoilage. It is heated in an open vessel to about 66°C and
cooled at room temperature. It can also be flash pasteurized by passing it
through aluminium pipes surrounded by hot water or steam at 66°C. Bottled
vinegar is pasteurized by immersing the bottle in hot water till the vinegar
inside attains a temperature of 60°C.
Colouring: Caramel colour, the only permitted colour in the case of vinegar,
is employed for colouring vinegar. At present malt and fruit vinegar are
made in India in a limited way only.

77
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Types of vinegar
Six types of vinegar are given here.
Fruit vinegar: Grape (grape vinegar), orange, jamun, pineapple and
apple (cider or apple cider vinegar)
Potato vinegar: Starch is extracted from potato and hydrolysed by the
diastase enzyme before fermentation.
Malt vinegar: Barley is commonly used for its preparation. The starch is
saccharified by diastase before fermentation.
Molasses vinegar: Molasses are diluted to 16% total soluble solids, neu¬
tralized with citric acid and then fermented.
Honey vinegar: It is prepared from low grade honey.
Spirit vinegar: Produced by acute fermentation of dilute allyl alcohol. It is
also known as grain distilled or white vinegar.

Steps involved in vinegar production

• Conversion of the sugar in fruits into alcohol by yeast (alcoholic fer¬
mentation).
• Conversion of alcohol into vinegar by acetic acid bacteria (acetification).
Anaerobic fermentation: Saccharomyces ellipsoideus, S. mater, S.
cerevisiae are the organisms involved in the anaerobic fermentation.
Yeast (25-27°C)
C6H1206-> 2 C2H2OH + 2C02

Anaerobic condition
Glucose or fructose fermentable sugar <-> Ethyl alcohol + carbondioxide

Aerobic fermentation: Acetobacter species is involved in this condition.

Acetic acid bacteria

C2H5OH + 02-> CHgCOOH + H20
Aerobic condition

Ethyl alcohol + Oxygen-> Acetic acid + water

Outline scheme of vinegar production

Fruit, grain, root crop (starch)

Enzymes
Starch-> glucose + maltose

Fermentable mono- and disaccharides

(alcoholic fermentation)

1
Yeast
Glucose or fructose -> Ethyl alcohol + CO,

Ethyl alcohol (Acetification)

Aceto bacterium
Ethyl alcohol + 02 - -> Acetic acid + H20

78
 MICROBES IN FOODS

For acetic fermentation the alcohol content of the fermented mash is adjusted
to 7-8% by diluting with water. Mother vinegar containing acetic acid bacteria
is added (1:10 parts of mash).

Problems of vinegar products

Following are the problems of vinegar products.
Wine flower: Unfermented juice when exposed to air a thin film of yeast
is formed. It causes cloudiness and destroys alcohol.
(a) Filling the barrels.
(b) 20-25% of unpasteurised vinegar added.
(c) Spreading liquid paraffin on the surface.
Lactic acid bacteria: Cloudiness, 20-25% of unpasteurized vinegar
Insects and worms: Vinegar mites, vinegar cells—sterilization at 60°C.
The uses of vinegar in preservation are:
1. Acetic acid in the form of vinegar (4% acetic acid) has been used to
preserve pickled vegetables from antiquity.
2. Acetates of sodium, potassium and calcium are used in bread and
other baked foods to prevent ropiness and the growth of moulds, but they
do not interfere with yeasts.
3. The acid is also used in foods such as mayonnaise, pickles, effective
moulds, and its effectiveness increases with a decrease in pH, which would
favour the presence of the undissociated acid.
4. Sodium diacetate has been used in cheese spreads and malt syrups.
5. As treatment for wrappers used on butter.

CHEESE

No one knows who made the first cheese. The ancient Greeks revered cheese
so highly that they believed it to be a God gift. According to an ancient
legend, it was discovered when an Arab merchant carried some milk in a
pouch mude from a sheep stomach across the desert. The bouncing of the
camel, the heat and the chemical action of the pouch caused the milk to
separate into curd and whey.The whey satisfied the Arab’s thirst and the
curd was cheese. Cheese is a food manufactured from milk. Its early history
of development is not known but according to ancient records, cheese has
been used as a food for over 4,000 years. It was made during Biblical times
and it is believed that the knowledge of cheese making was brought origi¬
nally from Asia to Europe and was introduced into many parts of Europe
when the Roman Empire flourished. During the Middle Ages, important
contributions to cheese manufactures were made by monks in the monas¬
teries and mention of cheese is made in the monastery records.
Until about the middle of the 19th century, cheese was a farm industry
wherein cheese was made from the surplus milk produced on the farm. The
first cheese factory in the United States was built by Jesse Williams in 1851.

79
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Cheese is defined as the curd of milk (coagulated by rennet) separated

from the whey and pressed into a solid mass. Most of it is made from cow’s
milk, however smaller quantities are made from the milk of goats, ewes,
camels, rein deer and buffalo. Cheese is normally made by coagulation of
the milk by rennet and lactic acid. The curd is then broken and most of the
whey is removed. The partly dried curd is then ripened and sold as cheese.
It is difficult to classify cheeses into meaningful categories. In the broadest
classification, cheese can be grouped as natural cheese or as processed
cheese. The cheese made directly from milk is classified as natural cheese
and a limited number are also made from whey and combinations of whey
and milk. Processed cheese is made by blending and heating one or more
varieties of natural cheese. Processed cheese is further subdivided into pas¬
teurized cheese, cheese food, and cheese spread. In these products certain
other ingredients may be added. The composition of natural and processed
cheeses and most cheese-based products is specified, in the Definitions and
Standards of Identity under the Federal Food, Drug and Cosmetic Act of the
U.S. Department of Health, Education and Welfare.
Natural cheese is made directly from milk with or without ageing and
ripening by bacteria or moulds. More than 400 different types of natural
cheese is produced.
There are many known varieties of cheese. Most of these are named
after the town, community or region where they are made and, though known
by different names, many have very similar characteristics. On the other
hand, several different cheeses have the same name. These can be catego¬
rized according to hardness and method of manufacture (Shakuntala and
Shadaksharaswamy, 1987) as follows:
1. Low moisture (30%) very hard, ripened by bacteria; examples sapsago,
romeno, parmesan.
2. Moderate low moisture (38%) hard, ripened, by bacteria; examples
(no holes) chedder, goude, edam, provolone (with holes) swiss.
3. Medium moisture (45%), semisoft, examples (ripened by bacteria and
surface micro-organisms) hard, trappist, limburger: (ripened by interior blue
mould) roque fort, blue cheese.
4. High moisture (50-80%) soft, examples (ripened) camembert (unrip¬
ened) cottage, cream, neufchotel, ricotta, mysest.
Processed cheese is produced from natural cheese blended for uniformity
of flavour, texture and cooking quality. Examples of processed cheese are
American cheese, and processed Gruyere. Because of the addition of pre¬
servatives processed cheese is more stable than natural cheese. Processed
cheese spreads contain a higher moisture content to produce a more
spreadable consistency at room temperature. Both spreads and solid proc¬
essed cheese may include other additives such as milk solids, wine flavourings
and spices.

80
 MICROBES IN FOODS

Manufacture
The basic processes involved in the manufacture of most cheese are
quite similar. Milk, either raw, heated, hydrogenperoxide treated (where
permitted), or pasteurized is placed in a suitable vessel or vat holding up to
about 19,000 litres of milk. The temperature of the milk is adjusted gener¬
ally in range of 30-35°C, and suitable starter culture or cultures are added.
These cultures generally consist of lactic acid-producing streptococci or
lactobacilli. Additional culture are used to contribute specific characteris¬
tics in Blue cheese and Swiss cheese.
Cheese colour may be added to the milk to impart additional colour to
the cheese or to maintain colour uniformity throughout the year. Annnatto,
an extract from annatto seed, is added @ from 30-90 g/450 kg of milk,
depending on the demand of the market and the season of the year. In some
cheese where it is desirable to have a white product, it is permissible to
remove the natural colour contributed by the milk by a bleaching process.
Bleaching can be effected by the use of benzyl peroxide or by masking the
natural colour by the addition of substances such as chlorophyll or a blue
colour.
When the proper amount of acidity has been developed in the milk by
the starters, rennet is added. This time period of culturing is commonly
referred to as ripening and may range from zero to several hours, but is
usually from 15 to 90 min. Sufficient rennet extract to coagulate the milk in
the desired time is diluted approximately 20 times its volume in cold water
and added to the milk. After the rennet has been added and thoroughly
distributed, the milk is left in a quiescent state until it coagulates. After
20-30 min, the curd is normally ready to be cut. The coagulated milk is cut
into cubes of 3-5 cm. The curd knives used to cut the coagulum consist of
metal frames across which are stretched parallel stainless steel wires that
are spaced to give the desired sized cubes of curd. One of the position knives
has the cutting wires in a horizontal position and the other in a vertical
position. In some of the newer mechanized installations, cutting of the curd
is accomplished mechanically by knives attached to the stirring mechanisms
of the vat.
The end result by either method is the same and facilitates the removal
of whey from the curd. After the curd has been cut, free whey appears
between the cubes of curd and a slight film or skin forms on the outer
surface of the cubes. At this stage of curd making, conditions are designed
to control the expulsion of whey and to develop a uniform firmness in the
cubes. The rate and degree of whey expulsion is controlled by the rate of
acid development, by the temperature to which the curd and whey are heated
or cooked, and the time of exposure.
About 5-10 min. after the curd is cut, slow agitation or stirring is started.
The speed of agitation is gradually increased, so that the curd particles do
not meet together. Agitation, however, should not be so vigorous that the

81
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

curd particles are shattered. Depending on the type of cheese being made,
the curd is subjected to heating or cooking. The heating is generally started
within 15 min. after the curd is cut by applying steam in the jacket of the
vat. The temperature to which the curd is heated depends on the type of
cheese being made and on the types of cultures used.
As a general rule, the high moisture, soft-type cheese receives a rela¬
tively mild heat treatment, whereas some other types of cheese such as
Swiss cheese may be heated to temperature approaching 54°C. Cheddar
cheese is heated at about 38-41°C, and in some instances as high as 43°C.
After the desired temperature has been reached, it is maintained until the
curd is removed from the whey.
Up to this stage of curd making, the basic procedures of manufacture
are quite similar for most types of cheese. There are variations in the degree
and manner in which the various steps are accomplished; all of which pre¬
pare the curd for subsequent steps in the manufacture of the particular
type of cheese being made.

Cheddar cheese
In the manufacture of cheddar cheese the general basic steps of cheese
making are followed until heating the curd or cooking is completed. The
curd is cooked to a temperature of about 36-41°C and held at the tempera¬
ture until the required amount of acid has been developed and the curd has
acquired the desired degree of firmness. Salt is added to the milled curd to
give a salt content in the finished cheese of about 1.5-2.0%. Cured chedder
cheese has a mild acid taste and aroma and no real cheese flavour. The
agents responsible for the changes that occur in the cheese during ripening
include the enzymes and the micro-organisms originating in the milk, starter
and rennets. The chemical and bacteriological changes that take place and
relationship to curing are not very well understood. The rate of ripening of
cheese is influenced by several factors, among which the most important
are temperature, pH, salt content, water content and season of the year as
it affects the composition of the milk.

Other chedder type cheeses

Besides cheddar cheese, the family of cheeses usually included in the
chedder family include stirred or granular curd, colby, washed curd, and
monetary jack. All of these are sometimes referred to as American cheeses.

Swiss cheese
Next to cheddar, Swiss cheese is the most popular single variety of cheese
in the United States. In Switzerland, Swiss cheese is called emmentaler
which is also an alternate name in the United States. This type of cheese
was first made in the Canton of Bern in the Emmental valley from which its
native name of Emmentaler originated. The most distinguishing character¬
istic of this cheese is the eye formation or holes that develop throughout the

82
 MICROBES IN FOODS

cheese as it ripens. In its manufacture, three different bacterial cultures are

usually used as starters, viz. Streptococcus thermophilus, Lactobacillus
bulgaricus or L.lactis and Propionobacterium shermardl. The thermophilus and
bulgaricus cultures are primarily the lactic acid.
Blue cheese
It is characterized by the distribution of a blue-green mould throughout
the cheese which results in a sharp, piquant flavour. Blue cheese is made
from cow milk which may be pasteurized, or homogenized and may be
bleached with benzoyl peroxide. A lactic starter is used to ripen the milk
and the milk is coagulated with rennet similar to the procedure used for
cheddar except that spores of the mould Penicillium roquefort are added
either to the milk or to the curd before hoping.
Paramesan cheese
Parmesan is a member of the family of ‘hard grating’ type cheeses which
were originally developed in Italy in the vicinity of Parma and is closely
related to a group of cheeses differing in size, shape, composition, and to
some extent, in the method of manufacture. These cheeses are character¬
ized by the hard brittle body which make them suitable for grating.
In the United States, Parmesan is made from a partially skimmed milk
by mostly the same basic procedures used for Swiss cheese including the
use of Streptococcus thermophilus and Lactobacillus bulgaricus or L. lactis as
starters. The curd is normally cooked to 46-51°C and when the curd is
properly firmed, it is placed in cloth-lined metal hoops and pressed. After
pressing, the cheese is salted either in brine or by dry salting. The period of
salting will vary depending on the size of the cheese, but normally ranges
10-20 days. The cheese is cured on shelves for a minimum of 10 months
during which time the cheese may be frequently cleaned and rubbed with
oil. During the curing at temperature 12-15°C, there is a gradual loss of
moisture so that when it is fully cured its moisture content is less than 32%
and the characteristic hard brittle body has developed.
Other cheese commonly included in this group are Reggiano, Veneto,
Parmigiano, Lodigiano, Lombardy, Emiliano, Venezza and Bogozzo or
Bresciano (Scott, 1981).
The Romano type cheeses are also closely related to the Parmesan group
but have more sharp piquant flavour. In the United States it must contain
not less than 38% fat in the solids.

Surface-ripened cheeses
As the name implies, are ripened by the growth of bacterial cultures or
mould cultures on the surface of the cheese. The enzymes produced by the
growth of these organisms penetrate into the cheese and produce the typi¬
cal characteristic flavour and texture of these cheeses. The two basic sub¬
families of this large family of cheeses are determined by the type of organisms
used for ripening.

83
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

The best known of the mould ripened varieties are Camembert and
Brie, both of which originated in France but have become popular all over
the world. Among the bacterial ripened cheeses are Brick, Meunster,
Limburger, Bel Paese of Italy, and Port du Salut of France. Brick and Mun¬
ster can no longer be considered true surface-ripened cheeses because as
presently made and handled have little or no surface ripening.
The surface-ripened cheeses is generally made from pasteurized milk
by the method similar to cheddar except that the process is modified to
retain more moisture in the curd which is dipped from the whey into hoops
and is not pressed. The cheese is usually brine salted but it may be dry
salted. After salting, the cheese is cured under suitable conditions of tem¬
perature and humidity.
Lactic acid bacteria perform an essential role (Desikachar et al, 1960;
Kiw and Chun, 1966; Ramakrishna Rao, 1977; Sanchez, 1977) in the pres¬
ervation and production of wholesome foods ranging from fermented fresh
vegetables such as cabbage (sauerkraut or korean kimchi) and cucumbers
(pickles) to fermented cereal yoguri (nigerianagi or kenyanuji), to sour dough
bread and breadlike products without the use of wheat or rye flours (Indian
idli/Philippine puto), to fermented milks (yoghurts or cheeses), to fermented
milk or wheat mixtures (Egyptian krish, Greek trahanas) to protein-rich
vegetable protein meat substitutes (Indonesian tempe), to amino or peptide
meat flavoured sources and pastes produced by fermentation of cereal, leg¬
umes (Japanese miso or Chinese soyo sauce), to fermented cereal fish or
shrimp mixtures (Philippines balao or balao; Philippine berong dalog), to
fermented meats (European salami, etc.)

Spoilage of the finished cheese

In general, the perishability of cured cheeses increases with their mois¬
ture content. Therefore soft cheese, like Limburger and Brie, are most per¬
ishable; and hard cheeses like cheddar and Swiss most stable. Most feared
among the spoilage organisms are the moulds that tend to grow on the
cheese surfaces and into cracks or trier holes. Even cheese that depends
partly on a specific mould for ripening may be damaged by other moulds.
Most natural cheeses have rinds that serve as some protection to the
anaerobic interior but usually are not dry enough to prevent mould growth.
The acidity of cheese is no deterrent to growth and the storage temperature
is not too low for such growth. Most moulds grow in coloured colonies on
surface or in crevices, without much penetration into the cheese, but some
kinds produce actual rots. Not only are discolorations evident but also off-
flavours are produced locally. Among the moulds that grow on cheese sur¬
faces (Frazier, 1978) are the following:
1. Oospora (Geotrichum) spp.: Oospora (Geotrichum) lactis, called the daily
mould, grows on soft cheeses and during ripening sometimes suppresses
other moulds as well as surface-ripening bacteria. The curd gradually

84
 MICROBES IN FOODS

becomes liquified under the felt. Oospora rubrum and 0. Crustacea cause
cheese cancer of Swiss and similar cheeses. Bumps of growth become filled
with a white, chalky mass.
2. Cladosporium spp.: The mycelium and spores of these moulds are
dark or smoky and give dark colours to the cheese. Most common is
C.herbarium, characterized by dark-green to black colours. Other species
cause green, brown or black discolorations.
3. Penicillium spp.: Penicilliumpuberulum and other green-spored spe¬
cies grow in cracks, crevices, and trier holes of cheddar and related cheeses
to give a green colour because of their spores. They may act on annatto to
cause mottling and discoloration. Penicillium casei causes yellowish-brown
spots on the rind, and P.aurantio-virens discolours Comembert cheese.
4. Monilia spp.: Monilia nigra produces penetrating black spots on the
rind of hard cheeses. Species of many other genera may discolour cheeses
and give off-flavours, e.g. the genera Scopulariopsis, Aspergillus, Mucor and
Altemaria.

REFERENCES

Desikachar, H.S.R., Radha Krishna Murthy, R., Rama Rao, G., Kadkal, S.B., Srinivasan, H.
and Subrahmanyan, C. 1960. Studies on Idli fermentation. I. Some accompanying changes
in butter. Journal of Scientific and Industrial Research 19C.
Frazier, W.C. and Westmold, D.C. 1978. Food Microbiology, edn 3. Tata McGraw-Hill Publish¬
ing Co. Ltd, New Delhi.
Girdhari Lai, Siddappa, G.S. and Tandon, G.L. 1967. Preservation of Fruits and Vegetables.
Indian Council of Agricultural Research, New Delhi.
Kiw, H.S. and Chun, J.K. 1966. Studies on dynamic changes of bacteria during the fermenta¬
tion. Journal of Home Science 6: 12-18.
Ramakrishna Rao,G.S. 1977. Isolation, identification and characterisa-tion of a micro-organ¬
isms (Leuconostock mensuleroides) in fermented soy-idli better capable of hydrolysing
soyabean A-haemogglutinins. Bewda Journal of Nutrition 4: 21.
Sanchez, P.C. 1977 Shortened fermentation process for the Philippines rice cake (Puto).
Philhppine Agriculturist 61: 134-40.
Scott, R. 1981. Cheese Making Practice. Applied Science Publications Ltd, London.
Shakunthala, M.N. and Shadaksharaswamy M. 1987. Foods: Facts and Principles. New Age
International (Pvt) Ltd, New Delhi.

LEARNER’S EXERCISE

1. Write about fermented beverages in detail.

2. What are the beneficial effects of microbes in food processing?
3. Explain the various steps involved in preparing malt beverages.
4. What is vinegar? Explain steps involved in preparation of vinegar.
5. Enumerate in detail about the processing and types of cheese.
6. Write about harmful effects of microbes in human health.
7. Write about preparation of synthetic vinegar and its uses.
8. Explain about fermentation process and its advantages.
9. What are the factors that affect the growth and development of micro-organizms in foods?

85
 food
spoilage

S ince food is a sensitive commodity and directly affects human health

and safety, it needs special care in handling right from raw material
through processing, packing and transport to the consumption point. Spoil¬
age in terms of food relates to decay and decomposition of undesirable na¬
ture. Food spoilage is directly related to poor sanitary practices and improper
food handling. When foods spoil, they undergo chemical and physical changes
that may render the food inedible and hazardous. The two main causes of
food spoilage are the growth of micro-organisms, including bacteria, yeasts,
and moulds, and the action of enzymes that occurs normally in the food.
Additional causes include non-enzymatic reactions in food, such as oxida¬
tion, mechanical damage, like browning and damage from rodents and in¬
sects. All foods deteriorate, some more rapidly than others (Ayens et al,
1979).
The major types of spoilage of foods and beverages are microbiological,
biochemical, physical and chemical.

MICROBIOLOGICAL SPOILAGE

There are thousands of known species of micro-organisms, not all of these

are harmful. Many are valuable and useful in the preservation of food, the
production of alcohol, or the development of special flavours. Those used in
food production are specially cultured and employed under controlled con¬
ditions. Microbial activity is considered to be a primary cause of food and
beverage spoilage. Micro-organisms are found everywhere—-in the soil, air,
and water, and on fruits and vegetables. The main factors that initiate the
growth of micro-organisms are suitable temperature, moisture, and a
substrate to live on, such as foods and beverages. There are three common
forms of micro-organisms, viz. (i) bacteria (n) moulds, and (rii) yeast.
In order to grow, all micro-organisms need food, a favourable moisture
content, and a favourable temperature. Because, in food preservation, it is
impossible to eliminate food as a factor in microbial growth, attention must
be given to the control of other conditions that aid growth.

Moulds
Moulds are able to utilize different kinds of substances, from very
simple to complex, for food. In general, they are aerobic, requiring oxygen

86
 FOOD SPOILAGE

for growth. They can also grow over a wide range of pH, from quite acid to
fairly alkaline (pH 2.0-8.5). They grow most rapidly at temperatures of
20-35°C and in a moist still atmosphere. However, they may grow with very
little moisture. Low temperatures retard their growth but moulds may still
grow at the temperature that prevail in the ordinary refrigerator (10—15°C).
Boiling temperatures somewhat below boiling (71-82°C) are adequate even
for spore destruction, if maintained for a sufficient time. The time is variable
according to conditions. If no spores are present, temperatures below boiling
are adequate for mould destruction. Some moulds will not grow in bright
sunlight but others grow in either darkness or light (Oseen and Bennon,
1970).
In general, moulds require less moisture than most yeasts and bacteria
and because they are also adoptable to many conditions of acidity and tem¬
perature. They are commonly involved in the spoilage of food. They will grow
on sweet foods, such as jellies or jams. They commonly occur on meats
(even cured meats), on cheese, milk and other protein foods. They grow on
fresh fruits, vegetables, and on cereal products.
A few moulds are pathogenic, causing diseases in plants such as potato
blight, and skin infections in man such as athelete’s foot and ringworm.
Ergot, a fungus that attacks rye, can produce a serious illness (known as
ergotism) in people who eat bread made from the infected grain. One of the
most spectacular developments in medicine in this century was the discovery
of penicillin and other antibodies produced by moulds.
Most moulds are probably not harmful. However, aflotoxin has been
produced by certain moulds, such as Aspergillus flavus which grow on
groundnut, wheat and other cereal grains, and cause illness and death of
animals (Frazier and West hoff, 1978). This is not a problem with men in
our country but further investigation of the use of mouldy cereals in certain
parts of the world might be of importance.
Moulds are larger than bacteria and are more complex in structure.
They are members of the plant family and composed of many cells, usually
cylindrical or tubular shaped. They grow in a network of hair like fibres
called mycelia and produce fruiting bodies that yield spores. These organisms
can penetrate the smallest opening, are tenacious, and become anchored to
a substance by their hair-like fibres. Moulds are probably the most common
type of spoilage organisms that can be identified by the naked eye. They are
recognized by most food service personnel. Examples are bread mould and
the mould that forms on the surface of meats and cheese products. An
outgrowth of mould contamination that is generally readily identifiable is
the odour referred to as mildeway.
Some moulds play valuable roles in food production. Certain varieties of
cheese, like Roquefort and Camembert, are ripened by moulds. They are
used for the commercial production of certain enzymes, such as amylase for
bread-making, production of citric acid. They are also used in making certain

87
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

oriental foods, such as soya sauce. The most important moulds are Penicillium
spp. (blue moulds), Aspergillus spp. (black moulds), Mucor spp. (gray moulds),
and Byssochlamys fulva.

Yeasts
Yeast cells are larger than either moulds or bacteria, measuring about
20 m in length. Yeasts are unicellular plants, spherical or ellipsoidal in
shape, and play an important role in the food industry. They produce enzymes
that have a favourable effect on certain chemical reactions, such as leavening
of bread and the production of alcohol and glycerol. Yeasts can induce un¬
desirable reactions in such items as citrus juices and fruit-flavoured drinks.
The result of uncontrolled fermentation is generally identifiable by a sour
taste.
Yeasts are usually aerobic. They may play useful or harmful roles in
foods. Yeast fermentations, chemical changes in which enzymes produced
by the yeast cells convert sugar into alcohol and carbondioxide, are important
in the production of such foods as bread, vinegar, beer and wine. Yeasts are
also grown for food and for the production of some enzymes. Yeasts are
undesirable when they grow and ferment fruit juices, syrups, honey, molas¬
ses, and so on. Moist, sugar containing foods, especially those that are slightly
acidic like fruit juices are particularly susceptible to spoilage by yeasts.
Fermenting foods are full of gas bubbles and if the action continues, alcohol
may be converted into acetic acid. An accumulation of alcohol may finally
check yeast growth. Yeasts grow most rapidly at temperatures of 20-38°C.
As in the case of moulds, temperatures somewhat below boiling may be
adequate for destruction, if the time of heating is extended yeast growth is
inhibited by low temperatures and may be checked entirely in a concen¬
trated sugar solution (65% or greater). Boiling temperature destroys yeast
cells and spores.
The yeasts which spoil certain foods, e.g. fruit juices, jams and meat,
are normally referred as wild yeasts to distinguish them from those used
commercially in the production of alcoholic drinks and bread.
The economic importance of yeast is its ability to break down carbohy¬
drate foods into alcohol and carbondioxide. This process, known as alcoholic
fermentation, is anaerobic, i.e. takes place in the absence of oxygen. Yeast
contains a collection of enzymes known as zymase which is responsible for
the fermentation of sugars, such as glucose, into ethanol (ethyl alcohol) and
carbon.

Pseudo yeast
These are like true yeast but do not form spores. All the members of this
group are particularly unsuitable for fermentation purposes, as they produce
off-flavours and cloudiness.

88
 FOOD SPOILAGE

Viruses
These are the smallest of all micro-organisms, varying in size from 10 to
300 nm (1 nm = 10'9 m). Most viruses are not visible under the light micro¬
scope but can be observed and photographed with the aid of an electron
microscope. Viruses are acellular, i.e. they do not have a cellular structure.
They are made up of a central core of nucleic acid surrounded by a protein
coat. They cannot feed, grow or multiply in isolation; they must always live
as parasites in larger living cells. A virus particle attaches itself to a cell and
the core of the virus penetrates and directs the life of the cell, so that many
more virus particles are formed.

Bacteria
Bacteria are microscopic unicellular organisms of varying shape and
size. Most common shapes are spherical, rod, and spiral. A number of bacteria
produce spores which are resistant to heat and chemicals. Commercial steri¬
lization temperatures normally will deactivate these highly resistant spores.
However, bacteria are measured in units called microns (m). Most common
bacteria range from 1 to 10 p or more in length, and about 0.5 p in diameter.
Bacteria are of many types and are widely distributed in air, soil, water
and in foods. Some types produce substances of desirable flavour and are
cultivated for their beneficial action. The lactic acid of butter milk, sreekhant,
fermented pickles, cheese, and butter (when made from sour cream) is an
example of a desirable flavour substance formed by bacterial action. Some
products of bacterial decomposition cause spoilage of foods or cause them
to be highly toxic. Under favourable conditions bacteria multiply rapidly.
These favourable conditions are optimum moisture and temperatures from
20 to 55°C. Some types of bacteria have an optional temperature for growth
that is above 45°C and are called thermophilic. Those having low optimal
temperatures, such as refrigerator temperatures or below, are called
psychrophilic. Psychrophilic bacteria may cause particular problems in the
cold storage and freezing of foods, whereas thermophilic ones may create
problems in the canning industry. Bacteria with an optimal growth tem¬
perature of 20-45°C are called mesophilic. If bacteria require air or oxygen
they are called aerobic, if they do not require oxygen and grow better in its
absence they are called anaerobic. Facultative bacteria are capable of grow¬
ing with or without free oxygen. Each bacterium also has its own optimal pH
or degree of acidity for growth, but most bacteria grow best at a pH near
neutrality. Heat in the presence of acid is highly destructive to bacteria.
Therefore, in acid foods a boiling temperature maintained for a sufficient
time is adequate for the destruction of bacteria. Non-acid foods or foods of
low acid content (4.5) are the most difficult to preserve.
Certain bacteria, like those of the genera Bacillus and Clostridium, form
endospores or spores. These spores are more resistant to heat and other
destructive agencies than the vegetative cells. Bacteria in the vegetative state

89
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

may be readily destroyed in moist foods by being at boiling temperature for

longer time. Spores, however, particularly in low acid foods require tem¬
peratures higher than boiling for their destruction in reasonable time periods.
Pressure cookers are used to achieve higher temperatures.
The important groups of bacteria are:
Bacillus Rod shaped
Coccus Spherical
Coccobacillus Oval
Aerobes Require atmospheric oxygen for growth,
e.g. Acetobacteraceti
Vibrio Short, curved rods
Spirillum Long, coiled threads
Facultative anaerobes Can grow with or without atmospheric oxy¬
gen
Obligate anaerobes Do not grow in atmospheric oxygen
Mesophiles Require a temperature below 38°C for
growth
Obligate thermophiles Grow between 38 and 82°C
Facultative thermophiles Grow over the whole range of tempera¬
tures, covered by mesophiles and obligate
thermophiles and below.
Psychrotrophy Grow fairly well at refrigeration tempera¬
tures and some can even grow slowly at
temperatures below freezing.

ENZYMATIC SPOILAGE (BIOCHEMICAL SPOILAGE)

Biochemical spoilage, probably, the second greatest cause of food deteriora¬

tion, is caused by natural food enzymes. These are complex catalysts that
initiate many complicated reactions. If enzymatic reactions are uncontrolled
the off-odours, and off-colours may develop in foods and beverages. Many
foods contain natural enzymes, which under certain conditions produce
significant changes, such as enzymatic browning in apples. When the fruit
is peeled and exposed to air, apples turn brown due to enzymes activated by
oxygen. Natural tendering or ageing of meat is a desirable result of en¬
zymes. However, conditions favouring these reactions can sometimes cause
deterioration due to the undesirable growth of micro-organisms.
Micro-organisms that proliferate in various foods and beverages pro¬
duce enzymes that induce significant changes, e.g. production of alcohol by
enzymes derived from yeast. Enzyme formation can be controlled in the
same manner as micro-organisms. Heat, cold, drying, the addition of cer¬
tain inhibiting chemicals, and radiation are the principal means used to
control and inactivate natural food enzymes.

90
 FOOD SPOILAGE

Enzymes are organic catalysts produced by living cells. A catalyst is a

substance that changes the rate of a reaction without itself being used up in
the reaction. Enzymes may catalyse different chemical reactions in plants
and animal tissues. For example, they are responsible for chemical changes
occurring in ripening of fruits and maturing of vegetables. Enzymes are
proteins and may be responsible for certain undesirable chemical changes
in preserved foods. Boiling temperature is adequate to destroy enzymes, as
in the blanching of vegetables before freezing but sufficient time must be
allowed for adequate penetration of the heat throughout the substances
being heated.
Many reactions in plant and animal tissues are activated by enzymes.
The changes in foods during storage can be produced both by enzymes
present in the food or by enzymes from micro-organisms that contaminate
the food. A good example of the former is the ripening of banana due to the
enzymes present which hasten the ripening process. After some time the
fruit becomes too soft and unfit to eat. If there is a bruised spot on the fruit,
yeast can grow and produce enzymes which spoil the fruit.
Enzymes convert starch into sugar, proteins into amino acids, and pec¬
tin into pectic acids and this change the constituents of food. Some fruits
and vegetables turn brown when damaged or when their cut surfaces are
exposed to air due to the presence of enzymes phenolase, peroxidase and
polyphenol oxidase. Their actions can be easily controlled by regulating the
temperature and excluding moisture and air. Enzymes can act between 0°
and 60°C. The optimum temperature of action is usually 37°C, the rate
varying directly with temperature. All enzymes are inactivated at 80°C.

SPOILAGE BY INSECTS, PARASITES

AND RODENTS

Worms, bugs, weevils, fruit flies and moths may damage food and reduce its
nutrient content and render it unfit for human consumption.
Insects are particularly destructive to fruits and vegetables. The loss of
food due to insects varied 5-50%, depending on the care taken in the field
and during storage. Insect infestations in grains, dry fruits, and spices, are
generally controlled by fumigation with methyl bromide, ethylene oxide or
propylene oxide. Apart from the direct loss through consumption of the
food, insects cause greater damage by the bruises and cuts they make in
foods, thus exposing them to microbial attack resulting in total decay.
A common parasitic infection of foods is Entamoeba histolytica. Rats
contribute substantially to destruction of food in countries where they are
not controlled. Besides, they consume large quantities of food, contaminate
it with their urine and droppings which harbour disease-producing bacte¬
ria. Rats spread human diseases such as typhus, plague, typhoid etc.

91
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

MECHANICAL SPOILAGE (PHYSICAL SPOILAGE)

Physical spoilage can be brought out by temperature changes, moisture

and dryness. Excessive heat destroys emulsions, dehydrates food, and de¬
stroys vitamins. Extreme cold can also cause deterioration. A common ex¬
ample is the freezing of milk which breaks the emulsion, causing fat to
seperate. Some sauces exhibit a similar tendency. Excessive moisture in
powdered beverage concentrates, such as instant tea or hot chocolate, can
support the growth of mould or bacteria. Such moisture levels need not
extend throughout the entire product to allow growth. Surface moisture will
cause lumping, caking, stickness and crystallization in a product. These
conditions are prevalent in vending machines and counter served iced tea
or hot chocolate dispensers. Entrapped moisture in protective film pack¬
ages can damage the contents, creating conditions suitable to support the
growth of microorganisms.
It is the major factor responsible for spoilage when the fruit and vegetable
surface is mechanically damaged; it gives scope for the microorganisms to
enter and cause secondary infection. There are different types of mechanical
injury.

Cut injury
Occurs when the product is pressed against the sharp edges of packing.

Compact injury
Due to overloading the container especially in case of soft fruits
like berries.

Vibrational injury
Occurs during transit if the containers are underloaded resulting in
striking of the contents among themselves or with the container.

Impact injury
Results in damage to bottom layer and is very difficult to control.

CHEMICAL SPOILAGE

Chemical spoilage may be caused by the interaction of certain ingredients

contained in a food or beverage with oxygen (air), by light, or by time (ex¬
tended storage). Temperature changes can accelerate reactions producing
undesirable chemical changes. In addition, the reaction of incompatible sub¬
stances in a food or beverage can lead to chemical spoilage. Examples of
this are the effects of certain metals on the brewing of coffee and in deep fat
frying, and the effect of iron, copper or other impurities, such as high alka¬
linity in water used for carbonated beverages.

92
 FOOD SPOILAGE

CHANGES IN FOOD CONSTITUENTS DUE TO SPOILAGE

The characteristics of a food influence the type of micro-organisms that can
grow in it and thus determine the changes in its appearance, flavour and
other qualities.
Proteins are degraded by proteolyte organisms. Many bacterial species,
specially spore forms, gram-negative bacilli such as pseudomonas and a
few cocci can degrade protein. Moreover, spoilage by moulds is also com¬
mon. Fats are digested by relatively few micro-organisms, mainly moulds
and a few gram-negative bacteria. Fats become rancid due to hydrolytic
decomposition to mal-odourous fatty acids.
Carbohydrates are affected by carbohydrate-fermenting micro-organ¬
isms, particularly yeasts and moulds. Bacterial species of the genera
Streptococcus, Leuconostoc and Micrococcus are saccharolytic and can also
attack carbohydrates. The degradation reactions are described below.
Protein + proteolytic micro-organism —> amino acids + amines + ammonia + hydrogen sulphide
Fat + lipolytic micro-organisms-> fatty acids + glycerol
Carbohydrate + fermentation micro-organisms-> acids + alcohols + gases

Factors affecting spoilage

Moisture: Moisture is required for chemical reactions and microbial growth.
Foods with a high percentage of water deteriorate fast. Variations in surface
moisture due to changes in relative humidity can lead to lumping and cak¬
ing, surface defects, crystallization and stickness in foods. Condensation of
even small amounts of moisture can result in multiplication of bacteria and
moulds.
Micro-organisms require at least 13% free water in foods for their growth.
Moulds require the least free water and bacteria the most. Foods having
high sugar or salt concentration do not support the growth of bacteria and
are generally inhibited by a salt concentration of 5-15% whereas many
moulds and some yeast can tolerate more than 15%. A sugar concentration
of 65- 70% is required to inhibit moulds but 50% inhibits bacteria and most
yeast. Foods with high sugar or salt content are, therefore, most likely to be
spoiled by moulds.
The pH of nearly all foods is below 7.0. Foods are classified as acid or
non-acid, depending on whether the pH is below or above 4.5. Most fruits
are acid foods, while nearly all vegetables, fish, meats and milk products
are non-acid. The low pH of acid foods prevents the growth of most bacterial
species. Such foods are spoiled mainly by yeast and moulds. Non-acid foods
are particularly subject to bacterial spoilage, but also support growth of
moulds under favourable conditions.
Temperature, aerial oxygen, light and duration of storage are the im¬
portant factors that influence the type of microbial growth and spoilage of
food during storage.
Temperature: Heat and cold, though play a role in food preservation, con-

93
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

tribute to deterioration of food if not controlled. The rate of chemical reac¬

tion doubles itself for every 10°C rise in temperature. Excessive heat brings
about protein denaturation, destruction of vitamins, breaking of emulsions
and desiccation of food by removing moisture. Several fruits and vegetables
deteriorate on keeping even at the temperature of refrigeration (4°C). The
deterioration includes off-colour development and surface biting. Banana,
tomato, lemon and squash should be stored at about 10°C for retaining
their quality.
Low temperature retards spoilage but even a sub-freezing temperature
of about 7°C does not prevent multiplication of all micro-organisms. Refrig¬
erated foods are therefore subject to spoilage by moulds and by some yeasts
and bacteria. Foods stored at 180°C remain free from microbial growth and
may even show a gradual decrease in the population of micro-organisms.
Foods and food products stored at room temperature or in warm locations
are easily spoiled by mesophilic and thermophilic organisms.
Oxygen: Atmospheric oxygen may bring about undesirable changes in
food such as destruction of food colour, flavour, vitamin A and C. Oxygen is
necessary for the growth of moulds and therefore it must be excluded from
food in the course of processing, by deaeration, vacuum packing, or flush¬
ing containers with nitrogen or carbondioxide and in some cases by the use
of oxygen-absorbing chemicals.
Light: Light destroys vitamin B2, A and C and also many food colours.
Not all wavelengths of natural or artificial light absorbed by food constituents
are equally destructive. Foods may be protected from light by impervious
packing or keeping them in containers that screen out specific wavelengths.
Duration: All the factors including deterioration of foods are time de¬
pendent. The longer the storage time, the greater the deterioration. Deterio¬
ration with time takes place with most foods except for cheese, wine and
other fermented foods which improve up to a point with agency. For enjoying
the best quality food it should be consumed before deterioration sets in.

REFERENCES

Ayens, J.C., Mundt, J.O. and Sandine, W.E. 1979. Microbiology of Foods. Freeman, San Fran¬
cisco, California.
Frezier, W.C. and West Hoff, D.C. 1978. Food Microbiology, edn 3, pp. 11-68. Me Graw-Hill
Publishing Co. Ltd, New York, New Delhi.
Oseen, H, and Bennon, M. 1970. Introductory Foods, edn. 5. Collier Macmillan Ltd, London.

LEARNER’S EXERCISE

1. What are the sources of contamination of fish?

2. What are the different method of preserving fish?
3. Write about types of spoilage that occur in pickles.
4. What are the ingredients that preserve pickles and explain their action?
5. What is spoilage and what are the causes for spoilage? Write in brief on the methods of
preventing spoilage of perishables.

94
Plant food products and
processing techniques
 Cereals and H
millets I

I n India, the Green Revolution of the sixties and seventies changed the
agricultural situation (Rao, 1995). The cereals that received a boost in
production from a situation of importing foodgrains to a position to export
rice and wheat (FAO, 1995).
The common cereals and millets consumed in India are rice, wheat,
maize, sorghum, finger millet (ragi) and pearl millet. The grains are rich
sources of starches or carbohydrates and form the main source of energy in
Indian diets. In view of their large intake, these grains are also an important
sources of several other nutrients in Indian diets, such as proteins, cal¬
cium, iron and B-group vitamins. Cereals do not contain vitamin A or vita¬
min C (Ramakrishnan and Venkat Rao, 1995).
Cereals are the foods consumed in large quantity and at greater fre¬
quency by a vast majority of population in the world. They comprise the
major segment of agricultural production of any country. In about 75% of
the countries of the world, cereals and millets form the staple food of diets.
In most developing countries, cereals and millets form the staple foods.
As their cost of cultivation and production is low, cost: benefit ratio is high
both in terms of yield and also nutrients. They can be stored easily and for
long periods at a low cost, as their moisture level is low. They can be con¬
sumed in bulk, they provide blandness to the diet, hence can be incorpo¬
rated in infant or invalid diets. Cereals and millets have a high satiety value,
prolonged emptying time of the stomach and even if consumed in large
quantities, do not have deleterious effects on health provided they are not
consumed at the cost of other foods.
The anatomical structure of all cereal grains is basically similar. Grains
of wheat, rye, maize and sorghum consist of fruit coat (pericarp) and seed.
These are called naked caryopsis. Grains of oat, barley and rice (covered or
coated caryopsis) have additionally, outside the fruit coat, the fused glumes
(palea and lemna) which constitute the husk. Main part of the grain, is
kernel (caryopsis) which includes the pericarp (fruit coat) and epidermis,
seed, endosperm and germ.
Under the husk the seed which includes the seed coat (testa) and a
pigmented strand. Immediately below this is the nuclear hyaline layer. Next
is the endosperm which comprises the aleurone layer and the starchy
endosperm. From the pericarp down to the starchy endosperm is called the
bran. The innermost part of the cereal grain is the germ or embryo.

97
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Cereals vary in size, maize being the largest and pearl millet the lowest.
They are usually spherical, lenticular or kidney shaped or even angular or
spindle shaped. The starchy endosperm of cereals is the largest portion of
the grain, and contributes to 76-90% of the grain weight. About 10% of
weight is contributed by the pericarp, testa and aleurone put together and
germ occupies 4-5% of the structure of the grain (except in maize in which
it takes up about 12% of the weight due to 10-13% scutellum present in it).

RICE

It is the most extensively grown in India and it forms the staple article of
diet of a majority of people in the country. Carbohydrates in the form of
starch, which provide energy to the body, constitute the bulk of the rice
grains. Rice provides about 350 calories/100 g dry weight. The protein con¬
tent of rice is only around 7%, which is not an appreciable amount. Since it
is consumed in large quantities, the total amount of protein that is clearly
ingested through rice is significant. Though the protein content of rice is
low, as compared to wheat, the quantity of rice proteins is superior to wheat
proteins. Rice protein however is deficient in lysine and threonine, as com¬
pared with a protein of high-quality like egg protein. However, when rice is
eaten with pulses, as is the common practice in India, its protein quality
improves due to the mutual supplementary effect between cereal and pulse
proteins, as the latter contain adequate quantities of these two amino acids.
Rice is a covered caryopsis, slightly smaller than wheat, is flattened later¬
ally, has a small point at the end of the distal from the germ. There is no
ventral furrow. The proportion of husk in rice grain averages 21%. Rice
grains are classified according to kernel length, weight, shape and described
as round medium or long and defined by the ratio of length to breadth. The
structure of rice grain is given in Fig. 8 (Magnus Pyke, 1981).
 CEREALS AND MILLETS

Rice is a poor source of fat and minerals, especially calcium and iron.
Therefore, rice-eaters must depend on other sources such as green leafy
vegetables for mineral supplementation. Rice is also a poor source of caro¬
tene or provitamin A, but is an important source of B-vitamins. Since most
of these vitamins are present in outer layers, polishing (removal of bran) to
produce the white rice for sale, reduces B-vitamin content of different de¬
grees depending on the extent of polishing. Highly polished rice has there¬
fore very low level of B-vitamin. It is better to consume rice which is not
polished too much. Parboiling, which involves seeling in water and steam¬
ing of paddy, results in movement of vitamins present in the outer layers
into the endosperm of the grain. Hence milled and polished parboiled rice
retains most of the vitamins. Consumption of parboiled rice, is therefore, to
be preferred to consumption of raw rice.
Rice is generally washed first and then cooked in excess of water. The
gruel present in cooked rice is then drained off. Since B-vitamins easily
dissolve in water, these procedures result in significant losses of the vitamins.

Processing
The rice kernel is composed of four primary components, viz. hull or
husk, seed coat or bran, embryo or germ and endosperm. The primary ob¬
jective of milling rice is to remove the indigestible hull and additional por¬
tions of bran to yield whole unbroken endosperm. Rice milling operations
are relatively uncomplicated, abrassive and separatory procedures which
produce a variety of products dependent on the degree of bran removal or
the extent of endosperm breakage.
Milling is a series of mechanical operations which remove the hull, em¬
bryo and outer layers of the rice kernel (Fig.9a, 9b; and Fig. 10).

Rough rice Paddy

Cleaning
T
Parboiling
T
Dehulling —> Hulls
~T~
Brown rice
T
Whitening —>Rice polish
-±-
White rice
~T~

T
Milled Polished

Fig. 9a. Rice processing

99
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Cleaner
Centrifugal shelter

Motor HP Husk blower (aspirator)

Paddy seperator

Huller

Motor

Fig. 9b. Mini rice mill (Source. Rao, 1997)

Fig. 10. Basic operations and products of rice milling

100
 CEREALS AND MILLETS

The husk, pericarp and other outer layers of aleurone are removed.
Subsequently, inner aleurone layers etc. are removed. This is called polishing
of rice. Dehuskers, hullers and pearling machines are used in milling.

Huller operations
Under runner disk huller: This consists of two horizontal cast iron disks,
partly coated with an abrasive layer. The top disc is fixed in the frame housing
and the bottom disc rotates. The rotating disc is vertically adjustable so the
clearance between the abrasive coating of the disc can be adjusted. A vertically
adjustable, cylindrical sleeve regulates the capacity and equal distribution
of paddy over the entire surface of the rotating disc. By centrifugal force,
paddy is forced between the two discs and under pressure and friction,
most of the grain is dehusked. Adjustment of clearance between, discs is
critical and requires continuous rechecking to avoid excessive breakage or
insufficient huller efficiency.
Rubber roller disc huller: In principle, the huller consists of two rubber
rolls. One is in a fixed position, the other is adjustable to obtain the desired
clearance between the two rolls. The rolls are driven mechanically in opposite
directions. The adjustable roller running about 25% slower than the fixed
one. Both rolls have the same diameter varying between 150 and 250 mm,
depending on the plank capacity. They have the same width, 60-150 mm.
When paddy is fed between the rolls; the grains are caught under pressure
by the rubber due to the difference in speed, and the husk is stripped off.
Efficiency of rubber rolls is unfavourable in tropical countries due to high
temperature, humidity, which lead to wear and tear.
Husk separation: Discharge of rice huller contains a mixture of brown
rice, paddy husk, bran, dust, brokens and immature paddy grains. Nor¬
mally, bran and dust are separated through an oscillating sieve with fine
perforations and discharged as a waste product. However, they may be mixed
with bran and removed by bran aspiration cyclone system, separation of
brokens and immature grain before husk aspiration is essential because
both these commercial by-products would be lost as waste through the husk
aspiration system.
Whitening and polishing: Whitening is the removal of silver skin and bran
layer followed by polishing. Three kinds of whitening machines, viz. vertical
abrasive whitening cone, horizontal abrasive whitening cone, horizontal jel
pealer, are used.
Glazing: It is a coating with talcum powder and glucose after polishing to
give a transparent look to rice.

Parboiling
This is a traditional and ancient process practised in India and 15-20
tonnes of paddy is being parboiled. The process involves pre-cooking of rice
with the husk intact by application of a hydrothermal treatment to paddy.

101
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

The paddy thus treated is dried before milling. This results in gelatinization
of the endosperm starch of rice followed by its partial retrogradation, caus¬
ing significant changes in its original, physical, physico-chemical, eating
and cooking properties. Soaking, steaming and drying are the three meth¬
ods used in parboiling.
During parboiling process, a reversible swelling and fusion of the starch
granules occur that changes the starch from a crystalline form to an amor¬
phous one.
The various stages of parboling are depicted in Fig. 11.

Fig. 11. Various stages of parboiled or converted rice

The grain is soaked for a required time, thus moisture is absorbed by

paddy, it swells and volume increases. Big, concrete cement tanks are used
for soaking. The soaked paddy is exposed to steam and starch granules get
gelatinized. This is done in metal kettles. Drying is done to bring down the
moisture content and harden the grain. Sun-drying or shade-drying is em¬
ployed. Sun-drying causes greater breakage. In order to avoid bad smell
and colour, improved parboiling processes are being employed at the CFTRI,
Mysore, and the Paddy Processing Research Centre (PPRC), Thanjavur,
Karnataka.

CFTRI hot soaking process

This was developed to avoid bad smell. The paddy is soaked in hot water
(65°-70°C). Germ action does not occur in hot water, thus the smell is avoided.
Soaking time is reduced to 3-4 hr.

Chromate soaking process

This is developed by the PPRC, Thanjavur. Chromate @ 50 g/100 kg is
added to the soaking water which stops germ action and deletes smell.

102
 CEREALS AND MILLETS

The CFTRI also developed the pressure parboiling method. Soaking time
is only 30-60 minutes and steam is passed through the grain to raise the
pressure slowly from an initial 0.28-70 kg/cm2 to 1.412.11 kg/cm2 and this
is maintained for 20-30 min. In this method, the processing time is reduced
and the machine turnover is high. As the moisture content of the grain is
lower, drying time and cost are reduced.
A high temperature short-time process was also developed at the PPRC,
Thanjavur. Steeped paddy is parboiled and dried concurrently by applying
high temperature for a short time. Paddy steeped by a short-time processes
is fed into a mechanical and sand roaster. Hot sand continuously moves
forward and backward in a roaster. A built-in thermometer indicates the
temperature of sand. Traverse time in the roaster is only 40 sec., yet par¬
boiling and roasting both occur with about 10% moisture removed. The
paddy gets completely and uniformly parboiled and its subsequent cooking
time is less.

Advantages of parboiling
(i) It is harder than raw rice and resists breakage during milling. Thus,
milling losses are minimum
(ii) There is better head rice yield
(iii) It is nutritionally better with a higher content of B-complex vita¬
mins, removal of nutrients with bran is less
(iv) Cooking quality is improved
(v) Milled parboiled rice stores better than milled raw rice
(vi) It is a better material for oil extraction as bran from parboiled rice
contains more oil
(vii) Occurrence of free fatty acids is minimum in the oil
(viii) Parboiled rice loses less solid matter
(ix) The grains are separate and chewy.

Disadvantages of parboiling
(i) It has a bad smell due to prolonged soaking
(ii) It has a dark colour due to heat treatment
(iii) It requires prolonged cooking time and more fuel
(iv) Since the oil content is high the polisher may get choked
(v) The heat treatment may destroy anti-oxidants. Hence rancidity may
develop
(vi) Due to the high moisture content, mycotoxins may be formed
(vii) Drying cost is added to the total processing cost, extra capital in¬
vestment.

Non-waxy rice
Non-waxy rice (containing amylose in addition to amylopectin) has a
translucent endosperm, whereas waxy (0-2% amylose) rice has an opaque
endosperm because of presence of pores between and within starch granules.

103
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Major processed rice products

Processed rice products may be derived from rough rice, brown rice,
milled rice, cooked rice, broken rice, diy-milled flour, wet-milled flour or
rice starch (Fig. 12).

Cooked rice

Angkak, Cakes
(mochi),
Canned rice,
Congee, Mirin
and miso
Vinegar, Wines
(sake)

Puffed and
Beaten/flaked extrusion
rice fermented cooked rice
cakes
(idli dosa)
Puffed rice Antidiarrhoeal
preparation
Baby foods
Breakfast cereal
Snack foods

Cakes, various Food stabilizer

noodles, Flat Noodles
and extruded, Tablets
Rice paper/
wrapper

Fig. 12. Major processed rice products (Source: Juliano, 1993)

Pre-cooked and quick-cooking rice: Pre-cooked rice is used for rice-based

convenience food products in which non-rice ingredients are packed sepa¬
rately and mixed only during heating. Quick-cooking rice is that raw rice is
precooked and dried during which produce a porous structure after cooking.
Noodles: Flat and extruded round noodles and rice paper are tradition¬
ally prepared from wet milled flour that has been ground using either a
stone or a metal mill.
Rice cakes, fermented rice cakes and puddings: Wet-milled non-waxy or waxy
rice flour may be kneeded with water and converted to sweetened rice cake
by adding sugar and other ingredients before steaming. Idli (rice dumplings)
and dosa (rice pancake) are prepared in India from a mixture of parboiled
rice and blackgram (Phaseolus mungo) about 3:1 by weight, typically as
breakfast foods (Hesseltine, 1979; Steinkraus, 1983).

104
 CEREALS AND MILLETS

Instant rice: Whole grain rice may be pretreated under controlled cooking,
cooling and drying conditions to produce a quick-cooking instant product.
Typically, instant rices require less than five min. preparation time, as com¬
pared to 20-25 min. for regular or parboiled rice products. A variety of
processing schedules, including use of soaking, heating, cooking, vacuum
or steam pressure, and controlled dehydration, are used to render milled
rice suitable for rapid preparation. Use of these techniques enables hydra¬
tion and gelatinization of starch and yields an open, porous kernel surface
with minimum kernel damage. This pre-cooked product readily rehydrates
and softens to a palatable grain in boiling water.
Ready-to-eat cereals: Ready-to-eat breakfast cereals are prepared from
milled rice as flakes or puffs. Rice is frequently pre-cooked under steam
pressure, conditioned to uniform kernel moisture and passed through high
pressure smooth flaking rolls and toasted. Vacuum puffing of cooked grains
or flaked rice is common. Instant hot baby cereal is produced by drum
drying a slurry of rice flour. Thin sheets of cooked dehydrated cereal are
removed by surface scraping rotating steam heated drums. The sheets are
ground to yield thin flakes which readily hydrate and form a characteristic,
soft, pasty porridge.
Flaked rice: In the traditional process paddy is first soaked in warm water
overnight (30% moisture content). The water is drained out and the paddy
is roasted with vigorous stirring in batches of 1-2 kg with sand in iron pans
over direct fire in a furnace for about a minute. The sand is removed by
seiving, then the paddy is flattened either by pounding in a mortar and
pestle or as is common, by an edge-runner. This removes husk and a part of
the bran, as they have been rendered very brittle, while the kernel is flattened.
Studies have shown that prolonged flaking in the edge-runner causes heavy
breakage resulting in yields as low as 63%. Installation of two idle rollers in
the same edge-runner machine reduced the flaking time to about 60% re¬
sulting breakage and raised the yield to about 66%. This increased
the capacity by 40%, whereas increase in power requirement was 30-40%
only.
As a further improvement, the milling and flaking steps were separated
and the process made continuous. In this process, paddy is soaked in hot
water overnight and the soaked paddy is roasted in sand, passed succes¬
sively through the dehusker-aspirator, polisher and roller flaker and finally
dried. Yield of flakes was raised to about 70% with hardly any breakage.
Also, the flakes obtained were free of husk-bran specs and sand particles.
Other advantages of this process are recovery of pure stabilized bran and
also pure husk.
Puffed rice: This popular ready-to-eat snack product is obtained by puffing
milled parboiled rice. In the traditional process, rice is gently heated on the
furnace without sand to reduce the moisture content slightly. It is then
mixed with salt solution and again roasted on furnace in small batches with

105
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

sand on a strong fire for a few seconds to produce the expanded rice. Rice
expands about 8 times. The product retains the grain shape, is highly po¬
rous and crisp. Studies have shown that dry-heat parboiled rice gives better
puffing than steam-parboiled rice. Pressure parboiled rice gives still better
volume expansion (10-12 times). The conditions for best puffing were found
to be moisture content of rice at the time of puffing (after mixing salt) 10.5-
11%; salt 3-4 ml (saturated salt solution to 100 g of rice), sand 10 times,
temperature of puffing 250°C and time of puffing 10-11 sec. Puffing is also
done by more sophisticated methods such as gun puffing or over puffing
(Juliano and Sakurai, 1985).
Popped rice: This product is obtained by direct puffing of paddy. Recent
studies in this institute have shown that predrying paddy to 9% moisture
followed by raising the moisture to 14%, resting and puffing gave a much
better volume expansion (further by about 20%) than when the moisture is
directly adjusted to 14% and puffed.
Thus, several types of processing systems have been developed and are
in use. Mini rice mills and mills for minor cereals need to be evaluated for
capacity, energy, investment and versatility. This would enable design and
development of improved versions consistent with needs of developing coun¬
tries.
Flaked, popped and puffed cereals hold promise as basis for snack food
products. All these involve high temperature short-time (HTST) treatment
for which development of energy-efficient systems is required. A system has
to be developed to separate husked and unhusked pulses. There is a need
to develop test-milling equipment for evaluation of minor cereals and pulses.

Utilization of rice bran

It ontains 15% oil (average) and is a very valuable source of oil.
Rice bran oil: The using of rice bran oil is similar to that of other oils.The
steps involved in preparation of this oil are (Sekhon, 1989):

1. Dewaxing To remove wax

2. Degumming To remove phospholipids
3. Neutralization or deacidification - To remove the fatty acids
4. Bleaching To remove colour
5. Deodourization To remove smell
6. Winterization To remove saturated glycerides

Rice bran oil is rich in unsaturated fatty acids particularly oleic and
lenoleic acids. Crude oil with high acid values are mostly used as raw mate¬
rial for industrial manufacturing products, whereas those of low acid values
are used for human consumption as cooking and frying oil.
Rice bran: Because of its high fat and protein content rice bran is fed as
a concentrate to poultry, cattle and pigs. It has better nutritional values for
sheep and swine than for cattle and chicken. It is also used as a culture

106
 CEREALS AND MILLETS

medium for production of mushorooms. About 10% of delated rice bran is

used as fertilizer in Japan (Prabhakar, 1988).
Rice polishing: Rice polishing is used in breakfast cereals as a source of
dietary fibre, protein and vitamins. Rice is generally washed first and then
cooked in excess of water. The excess water present in cooked rice is then
drained off which contains water-soluble B vitamins. From the nutrition
point of view rice should not be washed too much, cooked in just enough of
water to prevent B vitamin losses. The nutritional quality of processed prod¬
ucts prepared from paddy such as flaked rice, puffed rice is almost similar
to that of rice (Luh, 1980).
The waxy rice flour has superior quality for use as a thickening agenc
for white sauces, gravies, puddings and in oriental snack foods. The flour
prepared from parboiled rice is essentially a pre-cooked flour. Rice flour has
steady demand for breakfast foods like idli, dosa, baby foods, meat products,
dusting powders, bread mixes and for formulations of pancakes and waffers.

WHEAT
The wheats of commercial importance belong to: (i) Triticumaestivum (com¬
mon hard wheat); (n) Tritium durum (durun wheat); (in) Triticum compactum
(soft white wheat). In wheat and rye, the lemma and palea are loose and
become free from the grain at threshing, forming the chaff. Wheat and rye
are thus naked caryopsis.
The wheat grain consists of germ or embryo (which is rich in protein
and oil), endosperm (which is rich in starch and is a fair source of proteins)
and various outer coverings such as pericarp, testa or seed coat, hyaline
layer and aleurone cell layer (Fig. 13). The relative per cent by weight of

107
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

different constituents of wheat grain is given in Table 13 (Magnus Pyke,

1981).
Table 13. Total constituents (%) of wheat present in the main morphological parts

Part Weight Constituent

(g/IOOg grain) Starch Protein Fibre Fat Ash

Pericarp, testa, aleurone 15 0 20 70 30 67

Endosperm 82 100 72 8 50 23
Embryo, scutellum 3 0 8 3 20 10

The distribution of water-soluble B vitamins in the grain is responsible

for considerable differences in vitamin content between the whole grains
and the milled or processed products.

Wheat milling
The degree of milling of wheat is known as the extraction rate. Whole
meal flour, which contains all the bran, germ, scutellum and endosperm of
the wheat grain has an extract rate of 100%.
Wheat flour forms the basis for much of the world’s food supply. World¬
wide, wheat is the most abundant food crop, based on area planted and is
essentially equal to rice in the amount harvested. The reason for the almost
universal appeal of wheat as a food is the unique taste and the light-leav¬
ened texture of the products produced. The light texture is not found in
other cereals. Products made from wheat include bread, cakes, cookies,
biscuits, pretzells, doughnuts, muffins, pasta, gruels, breakfast cereals, semo¬
lina etc. Each of the above could be subdivided into many forms.
Wheat needs to be pulverized or ground into fine powder (flour) before
preparing different products. The quality of wheat flour determines the suit¬
ability for a particular end-use. Therefore, milling plays an important role in
the utilization of wheat for various products. Different operations are in¬
cluded in the milling process (Fig. 14).
Wheat selection and blending: Sound, dry and sproutless wheat gives maxi¬
mum flour yield. Wheat grains with uniform and desirable quality should be
selected for milling. Flours of desired characteristics can be obtained by
blending different varieties of wheats in definite proportions.
Cleaning: Cleaning is done by different methods.
Wheat washing: Wheat is conveyed through a trough containing water
to the base of a centrifugal machine vigorously agitated and sun-dried. This
operation is effective in removing dirt from crease of kernels.
Screens: In screen separation, impurities are separated on the basis of
difference in size and shape. Screens are perforated metals with a selected
size and shape of apertures mounted on frames. The screens move horizon¬
tally by gyrating or reciprocating.
Milling separators: These separators work on the principle of particle

108
 CEREALS AND MILLETS

Wheat Break-rolls and scalping sieves

\r '

Purifiers
Coarse Fine
semolina semolina Mlddlin9s
Grading sieves

Reduction rolls,
Dressing sieves,

Fine wheat feed

Coarse wheat feed
Flour

Fig. 14. Simplified flow-diagram of the processes of flour milling (Source: Altrogg, 1957)

separation by width with aspiration. These separate fine impurities such as

dust, stones, sands, etc.
Magnetic separators: Metal pieces of iron or steel are separated on the
basis of their electromagnetic properties.
Aspirations: Light materials such as chaff, straw, small seeds can be
separated from wheat grain by ascending air current because of their differ¬
ences in terminal velocity.
Specific gravity separators: The machine consists of a triangular shaped
table which is adjustably inclined to the horizontal, both from back to front
and from side to side and is capable of reciprocating from side to side. Re¬
ciprocation rate is adjustable. A current of air is directed up through the
table. Heavy particles tend to remain close to the surface of table and
move towards the higher side of the machine and vice versa.
Dry scourens: This process removes hair and dirt adherent to the grain
by friction. Wheat is fed to machine having a perforated metal cylinder. It is
impelled against rapidly revolving beaters, which also propel the grain to¬
wards the exit from the machine. Superficial dirt and beeswing are removed
by aspiration and are blown away by air currents.
Tempering: This is a process where water is added to the grain to raise
the water content to 15-19% in hard wheat and to 14.5-17% in soft wheat.
Tempering improves the physical state of grain for milling. Wheat is allowed

109
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

to LIFE in tempering bins for periods from 18 to 72 hr with little or no

temperature control. Water enters the bran and diffuses inward.
Conditioning: This involves use of heat for quick diffusion of water into
endosperm and bran. It improves milling properties with saving of time.
Three methods of conditioning include:
Warm conditioning: Wheat is conditioned for 60-90 min. at 46°C and allowed
for 24 hr before milling.
Hot conditioning: The procedure is similar to the warm conditioning except
that the temperature raises to 60°C or higher.
Steam conditioning: Transfer of heat is more rapid from steam than from hot
air. It requires less power and gives higher yield of flour.
Altrogg (1957) reported optimum temperature for wheat during steam
conditioning as follows:

Section of steam Hard and dry Soft and dry Soft wheat
conditioning wheat (°C) wheat (°C) (°C)

End of steaming 38-42 55-65 40-45

Heating 40 40 60
Cooling 40-25 40-25 60-25

Milling operations
In almost all modern flour mills, wheat is milled by rollers and the
various steps are described below:
Breaking: Wheat grains are passed through break rolls. Grains are
cracked. Four or five sets of rolls are employed, each taking stock from
preceding one. After each break, a mixture of bran, free endosperm and
bran containing endosperm goes into the next break roll and the process is
repeated until most of the endosperm is separated from the bran. The surface
of break roll has saw-toothed flutes which run spirally around the roll. The
number of flutes increases from first to tenth roll. The rolls are set horizontally
or diagonally. Horizontal rolls permit more uniform feeding of grain to the
rolls and thus allow faster roll speed and higher production.
Sifting: After each set of break rolls is a sifting or scalping machine.
Scalping system is a combination of sieving operations (plan sifters) and air
aspirations (purifiers). Plan sifter has flat sieves piled in tiers with increase
in fineness from top to bottom. The sifter rotates in a plane parallel with the
floor. The large pieces of bran with adhering endosperm are first removed,
then transferred to the next break roll. On finer sieves, bran and endosperm
are scalped off. The resulting flour and endosperm chunks (middlings) which
still contain bran particles, are transferred to purifier.
Purifying: Purifier consists of a long-oscillating sieve inclined downward,
through which air current is passed in the direction of floor to ceiling. Flour
gets stratified into bran and middlings of different sizes. The middlings are
taken to appropriate reduction rolls. The overtails including bran and bran +

110
 CEREALS AND MILLETS

endosperm are taken back to the break roll or to mill feed stock. The number
of purifiers may be up to 12 for a system with 4 break rolls.
Reduction: These reduce the endosperm middlings to flour size and fa¬
cilitate removal of the remaining particles. The coarse rolls produce middlings
of uniform size which are later transferred to fine rolls to produce flour.
Scratching: In addition to break and reduction system, a scratch system ;
is sometimes used as a standby to maintain proper release of endosperm j
from bran. The system consists of fluted rolls similar to lower break rolls
which scratch off the adhering husk or bran from endosperm.
Entoleter: The stock from earlier reduction roll is treated on specially
devised Entoleter machine which acts like a detacher and increases the
yield of flour (Shuey et al, 1977). The machine consists of a disc with con¬
centric rings rotating at high speed. If any living matter (e.g. insects, fungi)
is present, it gets killed because of the centrifugal force. The machine avoids
the use of chemicals to control the organisms.
Air classification: In this process, finished flour from roller mill is further
reduced in special grinders moving at high speed.
Following grinding, the product is separated in air classifiers into their
constituent fractions varying in protein content. Blending of these fractions
can give flours suitable for a particular end-use. Air classification is rela¬
tively inexpensive and has certain advantages, e.g. manufacture of more
uniform flours from different wheats; increase of protein content in break
flours and decrease of protein in cake and cookie flours; controlled particle
size and chemical composition; and production of special flours for special
uses.
Conveying system: Development of pneumatic conveying was an impor¬
tant advance for the milling industry (Shellenberger, 1965). Vacuum is ap¬
plied using pumps or fans. Besides transportation, an intake through roller
mills keeps rolls and flour cool during grinding.
This milling process is applied for hard wheats. Soft wheats are milled
generally by the same method with minor alterations such as processing
variable, grinding technique and stream selection (Nelson and Loving, 1963).
Ymamazaki and Andrews (1981) illustrated soft wheat milling with 6 vari¬
able break rolls and variable reduction pass system suited to accomodate
different types of soft wheat.
In durum wheat milling, the objective is to produce maximum yield of
highly purified semolina. The production of semolina is the same as that of
flour but milling systems differ materially in design. In semolina manufac¬
ture, impurities must be removed by cleaning and purification systems. The
rolls in reduction system are sizing rolls with wide gaps. These produce
coarse middlings to a uniform particle size. The sifting system in a durum
mill relies heavily on purifiers. The yield of semolina of durum wheat varie¬
ties is about 55% (Rahim et a/., 1976).
Durum is considered a premier raw material for macaroni. The heavier,

111
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

stiffer and gluey texture of durum dough suits macaroni very well. Less
water requirement is an advantage as macaroni is a dry product. Durum
wheats also yield more semolina than other wheats. Due to endosperm char¬
acteristics semolina from durum is stiff, stable and flour under pressure
and does not exhibit degree of elasticity as found in strong bread wheats.

Gluten
Among cereal flours, only wheat flour mill form a visco-elastic dough
when mixed with water. The visco-elasticity is due to the gluten, a protein
present in wheat. The gluten proteins are water soluble and thus, will swell
and interact. The large molecular size and low charge density of gulten
protein allows extraction with both hydrogen and hydrophobic bonds. Wheat
flour doughs are also unique in their ability to retain gas, due to slow rate of
gas diffusion within the dough. Another unique property of wheat flour
doughs is their ability to set in the oven during baking and thereby produce
a rigid loaf of bread. The ability to retain gas results in production of light,
leavened products attributed to gluten protein.
Chapaties are prepared from high extraction wheat flour or atta. Water-
absorption capacity of flour is one of the important characters which deter¬
mines the softness and pliability of chapaties. Usually water absorption of
68% is desirable. Sedimentation test is based on the fact that gluten protein
of flour absorbs water and swells considerably when treated with lactic acid
under certain conditions. Flours with sedimentation value of 30-37 ml are
suitable for chapati-making. Dough from weak flour is sticky and difficult to
roll and flatten into chapaties. Chapaties prepared from such flour have stiff
texture and poor-keeping quality. Dough from medium strong flour is strong,
stretchable, elastic, non-sticky and is most suitable for cfrapafz-making.
Chapaties should be made from flours having at least 2.5% sugar. Flours
with more than 150 mg maltose/10 g flour are desirable. Wheat containing
10-13% protein is suitable for cfrapaft-making. High protein content makes
chapaties tough and leathering, whereas very low protein intake results in
crumbly type chapati with poor texture and keeping quality.
For bread-making, the flour must absorb large quantities of water to
make a dough of desirable consistency and on baking it must give a large,
well-risen loaf of satisfactory volume, good crumb texture, texture and col¬
our of crust, aroma, taste and good-keeping quality. All these depend on the
gas production and retention, capacity of dough, when it is subjected to
fermentation. For adequate gas production, the flour should have sufficient
diastatic enzymes which degrade starch to sugar, which inturn, forms
substrate for the activity of yeast during primary fermentation. The dough
should have sufficient strength, elasticity and extensibility. Varieties suit¬
able for bread-making in mechanized baking should have high stability,
elasticity and baking strength.

112
 CEREALS AND MILLETS

Flour treatments
Certain materials are added to flour to improve its baking characteris¬
tics. Such additives as maturing agents, bleaching agents, self-rising ingre¬
dients and others are blended into the flour of the mill (Desrosier, 1977).

Factors affecting gluten formation and development

Variety of wheat: As mentioned earlier, hard wheats are better suited for
making bread as they have more gluten than soft wheats. Thus choice of
variety will depend on the characteristics desired in the final prepared prod¬
uct.
Amount of water added to make the dough/batter: Generally, gluten should be
well hydrated to develop completely. If the liquid content is insufficient, a
hard dough is formed and the gluten development may be poor. However
addition of excess water may produce a runny batter which may be difficult
to manipulate.
Kneading time and keeping time: Generally, greater the kneading or ma¬
nipulation of the dough or batter, greater is the gluten development. How¬
ever, over-manipulation may break the gluten net-work. In cake and muffin
batters and in the preparation of biscuits, manipulation is minimal, as com¬
plete gluten development is undesirable, whereas chapati and bread doughs
are manipulated well. Keeping time ensures complete hydration of the glu¬
ten in the dough. If keeping time of the dough is extended beyond a certain
optimal value it does not have any effect on the texture of the final product.
Thus chapati and bread doughs are allowed to rest after being kneaded.
Presence of fat/oil: Fat or oil added to the dough in large quantities hin¬
ders development of gluten. A small amount of oil is added to the dough.
Refined oil, butter or vanaspati are used in cakes and biscuits.
Fineness of milling: Wheat flour that has been milled finely has a greater
gluten development capacity than coarsely milled flour. Coarsely milled grains
have less surface area than finely milled flour, and thus are hydrated to a
lesser extent.
Bread wheat is one of the most important wheats of the temperate zones.

Triticale
Triticale is the first man-made cereal while the hybrid of wheat (Triticum)
and rye (Secale) was first observed in Germany in 1880. It was sterile and
no seeds were produced. In 1930 triticale was first studied extensively in
the former USSR but remained a scientific curiosity. In the same year it was
discovered that colchicine would double the chromosome number and triticale
plants treated in this way become fertile. Nevertheless, the first durum wheat
and rye hybrids, although being fertile, contained no endosperm and would
not grow. This was overcome by growing the germ in tissue culture. Thus
combining the two techniques of colchicine treatment and tissue culture,
fertile seeds were eventually obtained and in this way the first man-made
cereal was produced.

113
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Wheat popcorn
Popcorn has been a favourite traditional snack food in the United States.
Expansion volume is the most critical quality factor for popcorn. The texture
(tenderness and crispness) is positively correlated with popping volume.
Most commercial popcorn has a 30-40 fold expansion. Popping occurs at
about 177°C which is equivalent to a steam pressure of 2.5 tonnes/cm2
inside the kernel. The water in the kernel is superheated and at the moment
of popping gets converted to steam, which provides the driving force for
expanding the IP80 thermoplastic endosperm after the kernel ruptures
(Muller and Tobin, 1980).
The important wheat product extensively used in India in the prepara¬
tion of a variety of breakfast foods is semolina used for preparation of upma.
This is also the largest consumed wheat product in other countries under
the name farina. The cooking time of farina has been reduced by the addi¬
tion of disodium phosphate and an ‘instant’ farina is in the market. This
farina is ready to eat after a minimum boiling time. Farinas flavoured with
malt and cocoa are also marketed.
Other commonly used breakfast wheat products include flaked, puffed,
shredded and granular products, generally made from wheat, maize or rice.
The basic cereal may be enriched with sugar, syrup, honey or malt extract.
All types are prepared by processing which causes dextrinization rather
than gelatinization of starch. Wheat flake processing is shown in Fig. 15.

Fig. 15. Wheat-flake processing

Flaked and puffed cereal products can be sugar-coated. Sucrose syrup

containing other sugars (e.g. honey) is used for the purpose. The cereal

114
 CEREALS AND MILLETS

particles are placed in a bowl, and as it rotates, molten sugar syrup is slowly
dripped on the mass. By proper technique, a product with a hard transpar¬
ent coating that does not become sticky even under humid conditions can
be obtained.
The keeping qualities of breakfast cereals depend to a large extent on
their fat content. Thus, products with low-fat cereals or cereal fractions
keep well. The keeping quality also depends on degree of unsaturated fatty
acids in the fat. If they are present, permitted antioxidants may be used in
the preparation of the cereals. The nutritive values ofthe breakfast cereals
can be enhanced by the addition of appropriate nutrients in process of prepa¬
ration of the cereal.

Products
Shredded products: Mostly, wheat is used to prepare this product. Wheat
is cooked in water to gelatinize starch. The conditioned grain is fed into
shedders and material emerging as long-parallel shreds are received on a
slowly travelling band, a thick mat is built up by the superimposition of
several layers. The mat is then cut into desired shapes and baked at 260°C
for 20 min.
Granular products: These are prepared from wheat. A dough is made of
yeasted whole meal, wheat flour and malted barley flour. The dough is fer¬
mented for about 5 hr and the bread is baked. The bread is then broken up,
dried and ground to desired fineness.
Biscuits, cookies and confectionary products: These are low density baked
products and require soft wheats. In biscuits and cookie making, the wheat
should not contain more than 13.5% moisture, and protein content of the
flour should range between 7 and 8% (Hoseney and Roger, 1988). About 9-
10% protein in the flour can be used for cracker and sponge — baked prod¬
ucts. Ash content should be between 0.38 and 0.42%. Additions in biscuits
making include sweetening agents, shortening, emulsifiers, milk, salt and
aerating agents having agents like baking powder and eggs. Fruits and nuts
are used for taste and flavour. Jam and jellies are also used for this pur¬
pose. Synthetic colours and flavours are used to increase palatability.
Gold fingers: In addition to extensive use for baked products, wheat and
its products can be used to prepare a variety of snack products like gold
fingers and vermicelli etc.
Gold fingers are similar to extruded pasta products like vermicelli. It is
processed at high temperature, high pressure for short time, under control¬
led conditions of moisture (Uma Reddy and Jayashree, 1990). The raw ma¬
terial mostly maida is conveyed through a barrel with necessary pressure
and consequently heat generated. The material undergoes structural modi¬
fications and emerges as a texturized material. They are crisped crunchy
and like potato chips and are popular among children.
Hand-made vermicelli: Hand-made vermicelli is made with maida into very

115
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

fine threads and is very popular as the vermicelli. Delicious payasam (/cheer)
is made. It is a very fast process and does not require any costly machinery
or equipment.
Papad: Papad is very popular item and gaining market evenues in cities.
They are used as meal accomponiments especially on festive occasions. It
can be used as a leisure-time household activity and does not require spe¬
cial equipment. Papad is becoming home-level enterprise which is managed
exclusively by women.

SORGHUM

Sorghum (Sorghum bicolor) is of African origin. A large variety of wild and

cultivated sorghums are grown in the tropics and subtropics of the world.
Cultivated sorghums are grown chiefly for their grain which is an important
staple food in many countries of Africa and Asia, and is the principal source
of beverages in some countries. In India, sorghum constitutes an important
article of food, after rice and wheat. The whole grain or broken grain may be
cooked like rice or the whole grain ground to flour and used to make chapaties.
In other parts of Asia also it is used this way. In Africa, sorghum is used as
food in various forms as porridge, gruel and parched, popped or malted
grain. From a blend of wheat flour and sorghum flour, baked products like
muffins, bread and cakes can be produced. In advanced countries the grain
is used chiefly as an animal feed. Sorghum plants are widely used as fod¬
der, either green or as hay and silage. The sugar content of some sorghum
stem is high (sweet sorghum) and these are used for producing syrup. Sor¬
ghum grain is used as a source of starch in the fermented industry for
producing industrial alcohol and solvents.
Structure and composition: The structure of the grain of sorghum is similar
to that of other cereals, consisting of an embryo, a relatively large scutellum
and endosperm, enclosed in a seed-coat (testa) and a fruit-coat (pericarp).
The testa and pericarp are fused together. In the outer layer of the pericarp
and in some cases beneath the pericarp, there is a layer of pigment (Fig. 16).

Fig. 16. Structure of sorghum grain

/
116
 CEREALS AND MILLETS

The sorghum grain is small and rounded, varying in colour from off-
white to varying shades of red, yellow or brown. The grain size varies, the
weight ranging from 7.0 to 61 g/1,000 grains, with most sorghums weigh¬
ing 20-30 g/1,000 grains.
The chemical composition of grain sorghum is similar to that of maize.
Generally, sorghum has more protein than maize, a lower fat content and
about the same amount and proportions of carbohydrate components. The
proximate analysis of Indian sorghum grain indicates moisture, 11.9; pro¬
tein, 10.4; fat, 1.9; fibre, 1.6; carbohydrates, 72.6 and minerals, 1.6%. Min¬
erals present in the grain are calcium, magnesium, potassium and iron
(Shakunthala and Shadaksharaswamy, 1987).
In comparison with maize, sorghum grain contains approximately the
same quantities of riboflavin and pyridoxine but more pantothenic acid,
nicotinic acid and biotin. Nicotinic acid occurs in the grain in available form.
In general, the vitamins occur in much higher concentrations in the germ
than in the endosperm or the bran. The riboflavin contents of the germ and
bran are the same.
Starch is the major carbohydrate of the grain. The other carbohydrates
present are simple sugars, cellulose and hemicelluloses. The amylose con¬
tent of starch varies from 21 to 28%. Starch from waxy varieties contains
little amylose. Both waxy and regular starches contain free sugars up to
1.2%. Sucrose being the major constituent (0.85%) followed by glucose
(0.09%), fructose (0.09%), maltose and stachyose. Sorghum grain contains
no detectable amount of glucoside, but on germination, a cyanogenetic
glucoside dhurrin is formed and the concentration of the glucoside in a 3-
day-old seedling is 3.5% Dhurrin releases hydrogen cyanide on hydrolysis
leading to the poisoning of animals consuming such sorghum.
The protein content of the grain varies according to varieties and grow¬
ing conditions.The percentage of different protein fractions to the total pro¬
tein of sorghum grown in India is albumin 5: globulin 6.3: prolamine 46.4
and glutelin 30.4. Prolamin and glutelin are principally present in the
endosperm. Amino acid analysis of various protein fractions show that there
is better distribution of all essential amino acids in globulins than in
prolamins. Sorghum protein is superior to wheat protein in biological value
and digestibility. However, as an exclusive source of protein, B-vitamins
and minerals in the diet, sorghum is inferior to wheat. A vegetarian diet
based on some varieties of sorghum is somewhat better than a rice-based
diet (Shakunthala and Shadaksharaswamy, 1987). Sorghum lipid consists
mostly of triglycerides, phospholipids constitute about 5% of total lipids of
sorghum. Nearly half of the phospholipid is lecithin. Sorghum also contain
some, wax. The triglycerides are rich in the unsaturated fatty acids, oleic
and lirioleic, their percentage being 33 and 47 respectively (Shakunthala
and Shadaksharaswamy, 1987).
A few red-and-brown phenolic pigments occur in the pericarp and seed

117
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

top of several varieties of grain sorghum. These pigments are tannins ac¬
counting for 0.2-2.0% of the grain and are responsible for the low payabil¬
ity and digestibility of sorghum food products and for the off-colour of starch
obtained by the wet-milling of the grain. White or yellowish grains contain
very little tannins. Some varieties of sorghum grains contain anthocyanins.
Grains with yellow endosperm are rich in carotenoid pigments (up to 10
parts per million) but the white grains contain only traces (1.5 parts per
million).

Flaking of sorghum
Moistened sorghum grains are pearled in a polishing machine. The
pearled sorghum is malted, steamed under pressure and then flaked in a
roller flaker. The flakes thus prepared make an excellent snack food.

MILLETS

The name millet is applied to numerous small-seeded grasses which origi¬

nated in Asia or Africa. The major millet crops of India are pearl millet
(Pennisetum glaucum) or bajra and finger millet (Eleusine coracana) or ragi.
A number of other minor millets are grown, viz. the common millet or proso
millet (Panicum miliaceum), foxtail millet (Setaria italica) and kodo millet
(Paspalum scorbiculatum). These millets, along with maize and sorghum,
are considered as coarse grains and constitute the food of the economically
weaker sections of dryland regions in India.
Millets are hardy plants capable of growing where most other grain
cereals fail. They are mostly grown in areas with low rainfall, poor irrigation
facilities and low fertility. These are well suited for dry farming. In develop¬
ing countries, with the current rate of increase in population and with less
than adequate irrigation facilities, millets can adequately meet the demand
for additional food supply.

Pearl millet
It is widely cultivated and consumed by the local population in many
countries of Asia and Africa. It is usually powdered in a flour mill and con¬
sumed in the form of porridge, dumpling or unleavened bread. Dehusked
pearl millet can be cooked in the same way as rice and consumed.
The coarse grains contain 8-10% husk. The average chemical composition
of bajra grain is: moisture, 12.4; protein, 11.6; fat, 5.0; carbohydrates, 67.1;
fibre, 1.2 and mineral matter, 2.7% (Shakunthala and Shadaksharaswamy,
1987). The mineral matter is rich in calcium, phosphorus and iron. More than
50% of the phosphorus is as phytin which is a major factor for the poor digest¬
ibility of grain. The protein content varies from 8.8 to 16.1%. The protein con¬
tains a high proportion of prolamine, followed by the globulin and albumins.

118
 CEREALS AND MILLETS

Among the amino acids, tryptophan content is high and lysine content average
to low. The carbohydrates consist mostly of starch with smaller amounts of
sugar (1.2%), pentosans and hemicelluloses. The starch is composed of 32.1 %
amylose and 67.9% amylopectin. The grains are rich in thiamine, riboflavin
and niacin (Shankunthala and Shadastharaswamy, 1987).
About 85% of pearl millet produced in the country is used as food. It
constitutes the staple diet of nearly 10% of the Indian population. It is con¬
sumed after dehusking and cooked in the same way as rice. More com¬
monly, it is ground into flour and made into chapaties. It is also made into
thin porridge. The grain is sometimes eaten after it is parched, the product
being similar to popcorn. The grain is suitable for the preparation of malt.
An intoxicating drink is obtained from its malted seeds.
The grains, ground or softened by soaking in water, find use to a limited
extent as animal feed. The green plant serves as excellent fodder and is
cultivated in developed countries only for animal feeding. The starw is also
used as fodder but is of inferior quality.
The processing of pearl millet and other millets for industrial purposes
has not yet been developed. Pearling of pearl millet to about 8% polish leaves
results most of the germs intact and the nutritive value is not seriously
affected. Pearling improves appearance of the grain, and traditional dishes
prepared by using the flour from pearled grain will have a better look and
taste. The dry milling of the grain has not yet been developed. Wet milling
has been investigated, but because of the smallness of the grains it is more
difficult to degerminate it than maize and sorghum, although the potential
yield of oil from millet exceeds those from the other cereals. Separation of
protein from starch is also more difficult with this millet than with sorghum
or maize.

Finger millet
It is cultivated in some regions in India, Sri Lanka and Africa and con¬
sumed as a staple food. Several hybrid varieties have been developed which
give high yields and are disease resistant and nutritious. The grains of fin¬
ger millet are very small in size varying in diameter from 1 to 2 mm. They
vary in colour from deep brown to shades ranging from red to almost black.
There is also a race of ragi which gives white seeds.
Chemical composition: The protein content of the grain varies 6-9%, de¬
pending on the variety. Finger millet is a rich source of calcium in which
other common cereals are deficient. It is a good source of iron and phospho¬
rus. The grain is a good source of thiamine and a fair source of niacin and
riboflavin.
Proteins consist of a mixture of globulins, prolamin and glutelin. About
30% of the nitrogen present in the grain (mostly in the husk) is not ex¬
tracted even by dilute sodium hydroxide. The protein is a fair to good source
of all essential amino acids, the limiting amino acids, being lysine and
threonine.
119
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Proso millet
The grain (covered kernel) of common millet are small (1,000-kernel
weight varies from 4 to 10 g) and is of an oval or spherical shape. In oval¬
shaped grains length is 2.0-2.6 mm, width 1.5-2.1 mm, and thickness 1.3-
1.7 mm. In spherical grains length : width ratio is close to 1.0, while in oval
grains the ratio is 1.25 or higher. The surface of lemma and palea is smooth
and glossy. The kernel may be white, creamy yellow, brown, gray or black.
The hull percentage of common millet varies within the range of 14-23%
generally from 15 to 17.
The fruit- and seed-coats of common millet are thin and consist of out¬
stretched, colourless, almost empty cells. The aleurone layer is represented
by a single row of cells whose cross section is rectangular; the chemical
composition is typical for this layer. The endosperm consists of large thin-
walled cells of polygonal shape filled with starch and proteins and contain¬
ing pigments.
The average percentages of various parts of common millet grain (% of
the grain’s weight) are: hulls 16, fruit- and seed-coats 3, aleurone layer
about 6,endosperm 65-70, embryo 3-5. The protein content varies from 9
to 16. The amino acid composition of millet proteins is incomplete, as they
contain inadequate amounts of tiyptophan and lysine. Common millet grain
contains a rather higher amount of fat, which readily becomes rancid due to
its high acidity. The hulls contain especially large amounts of silicon and
potassium salts.

Uses of millets
Finger millet is the principal foodgrain of the rural population in India,
especially in the southern region. It is usually converted into flour and a
variety of preparations like mudde, chapati, dosa, porridge are prepared.
The grain is also malted and flour of the malted grain is used as a nourish¬
ing food for infants and elderly. Malting releases the amylases which
dextrinize the grain starch. An added advantage of malting finger millet is in
the production of an agreeable odour developed during the kilning of the
germinated grain. Malted finger millet or flour is called as ragi malt and is
used in the preparation of milk beverages. A fermented drink or beer is also
prepared from the grain in some parts of the country.
The nutritive value of ragi is better than that of rice and other cereals.
The husk forms 5.6% of the weight of the grain. The average composition is
as follows: moisture, 13.1; protein, 7.1; fat, 1.3; carbohydrates, 76.3 and
mineral matter, 2.2%. It is rich in calcium, phosphorus and iron; the cal¬
cium content is higher than in the common cereals and millets. Though its
phosphorus content is high, much of it (75%) is present in the form of phytin
phosphorus. It contains B vitamins, but is poor in B2. The major proteins of
ragi are prolamins and glutelins and they appear to be adequate in all the
essential amino acids.

120
 CEREALS AND MILLETS

Malting
Malting is a controlled germination process which activates the enzymes
of the resting grain, resulting in conversion of cereal starch to fermentable
sugars, partial hydrolysis of cereal proteins and other macromolecules. Barley
is the grain generally used in the production of malt which finds industrial
uses in brewing and distillery. A typical malt house flow sheet is given in
Fig. 17. In commerce, the term malt is applied to barley malt. Small quanti¬
ties of other cereals are used for malting and they are designated as wheat
malt, ragi malt, sorghum malt, etc.

Fig. 17. Typical malt house flowsheet (Source: Desrosier, 1977)

Both two-row and six-row hulled barleys are used in malting. In India,
mostly six-row barley is used to produce malt for brewing. Malts used in
brewing must have a low nitrogen content and this limits the use of nitrog¬
enous fertilizers in the cultivation of barley used for malting. The malt re¬
quired for the distilling industry is somewhat different from that used for
brewing; there should be a proper selection of barley used for malting pur¬
poses, depending on the use to which the malt is put.
The malting operation starts with the drying of the grain in a kiln, so
that the moisture content of the grain is between 10% and 14%. Control of
moisture content accelerates maturing of grain and sometimes improves
malting quality. After drying and cleaning the grain is stored for at least 3
weeks, before malting. This allows secondary ripening processes to occur,
so that the grain can attain full germinative power. For malting, the stored
grain is steeped in water. The time required for steeping depends on tem¬
perature and extent of aeration of the steep water. Generally, steeping con-

121
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

tinues for 50-70 hr, after which time the surplus water is drained off from
the grain which is then spread on the floor for 7-8 days, while germination
takes place. The grain malt is then kiln-dried to arrest enzymatic activity,
without destroying the enzyme. The dried and cleaned product is malt.
A high proportion of the malt produced is used in most countries in
brewing and manufacture of distilled liquors. A small portion is used for the
manufacture of industrial alcohol. In India, most of the malt produced is
used in brewing. Other uses of malt include textile desizing, pharmaceuti¬
cal preparations, breakfast cereals, malted milk concentrates, infant foods,
bakery products and candies.
Malt extract is prepared by mashing malt and concentrating the mash
liquors into syrup. It contains about 40-55% maltose, and small quantities
of dextrin, glucose and proteins. It has high nutritive properties and is pre¬
scribed as food during periods of convalescence and used in many pharma¬
ceutical preparations.

Traditional methods
Dry milling separates the grain into three components, germ, endosperm
and seed-coat. Milling techniques practised mostly depend on the end-use
of the products. Traditional milling is done by pounding in a mortar and
pestle to remove outer bran, with dry or slightly wet grain. After pounding,
the outer bran is removed by winnowing and the endosperm is pulverized in
the same pestle and mortar or gound in a small chakki. Pounding is a very
laborious and time-consuming process. Only 6 kg grain is produced to flour
by a person in about 4 hr. Quality of the products is often not very good,
because of high moisture content of meal and mixing of pulverized bran
with flour. Hence the usage of hand pounding is not advantageous to prac¬
tice in any food enterprise.
The dry-milling process starts with the cleaning of grains. The cleaned
grain is conditioned, by addition of water, to soften the endosperm, and
milled by the conventional roller mills, to separate the endosperm, germ
and bran from each other. The endosperm is recovered in the form of grits,
with the minimum production of flour. Yields of various fractions from the
dry milling process are grit, 76.7; bran, 1.2; germ, 11; and fibre, 10%. Bran
and germ are further processed, as in the case of maize,by dry milling for
the preparation of oils and feeds.
Another milling process for sorghum is pearling or decortication. In this
case cleaned grams are wetted by spraying water for 2-3 min. and immedi¬
ately milled in a rice holler, to remove a major part of the coarse fibre,
pigment and phytin, with minimum degree of cracking of the grain. A maxi¬
mum of 12% polishing can be carried out. This type of milling can give
products rich in protein (up to 27%), and which are also high in fat and give
a high yield of ash, but are low in fibre. These products are used in the
preparation of food products of high protein content.

122
 CEREALS AND MILLETS

Wet milling of sorghum is carried out by methods similar to that of wet

milling of maize. However, the milling of sorghum is more difficult than that
of maize because of the small size and spherical shape of the sorghum
kernel and the dense high-protein peripheral endosperm layer. Manufac¬
ture of starch is the main purpose of wet milling. However, some of the
pigments of the pericarp and subcoat of the grain leach out and stain the
starch. Thus, grains with dark-coloured outer layers are not satisfactory for
wet grinding.
Sorghum starch is indistinguishable from corn starch and can be used
interchangeably with corn starch in most industrial applications. Sorghum
oil obtained from germ fraction, after refining, is used for salads and gen¬
eral cooking. Kernel residues containing bran and gluten are processed as
cattle feed.

Improved methods
Improved milling methods include roller milling, pearling, impacting,
grinding and air classification. The roller millled products are reported to
have a higher production costs partly due to lower extraction rate. This may

Fig. 18. Mechanical dehulling of sorghum

123
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

not therefore be suitable for adoption to millets commercially. The pearling

technique has been applied successfully to sorghum and other millets.
With the intention of removing drudgery of millet processing and to
enable preparation of variety of foods, Acharya N.G. Ranga Agricultural Uni¬
versity with the help of Agro Industry has developed a dehuller suitable for
both millets and legumes. This dehuller runs on 3 h.p: motor and is easy to
handle. At a time 5-7 kg grain can be fed and it takes 5-8 min. for dehullng,
depending on the quality and variety of the gram (Vimala et al, 1990).
For pearl millet, extraction rates varied between 80 and 90% for similar
dehulling times. For elusine only 3 min. dehulling was required with extrac¬
tion rate of 90%. Mechanical dehulling improved physical appearance and
functional properties. Dehulling effectively removed the colour of all varieties
of sorghum. Steps involved in mechanical dehulling process are given in
Fig. 18. Mechanical dehulling reduces the drudgery. It converts millets into
convenient ready-to-cook grain and improves the quality of flour.
The process developed for sorghum flour and semolina is shown in Fig. 19.
Improvement in primary process itself has helped in getting fine sorghum
flour. Use of appropriate milling procedures and sieves help in getting semo¬
lina. Fine quality sorghum flour can be substituted in place of bengal gram

Fig. 19. Processing of sorghum semolina

 CEREALS AND MILLETS

flour and wheat flour or wheat semolina. In a similar manner, pearl millet,
ragi and maize flour and semolina can be obtained.

CONVENIENCE FOODS

Alternatives foods such as ready-to-cook mixes, infant and weaning foods,

dehydrated foods, breakfast foods, snack foods, baked products, flaked prod¬
ucts and popped products can be prepared with sorghum flour and semolina.

Instant food mixes

Ready-to-cook, idliand dosa mixes can also be developed, using sorghum
flour (Table 14).
Table 14. Composition of idli and dosa mixes

idli mix (% ingredients) Dosa mix (% ingredients)

Dehulled sorghum 61 Sorghum flour 30

(rava) (40 mesh) (60 mesh)
Blackgram dhal 30.5 Rice flour 30
flour (60 mesh)
Salt 3 Blackgram dhal 30
flour
Sodium bicarbonate 2 Salt 3.3
Citric acid 2.7 Citric acid 3.85
Sodium acetate 0.65 Calcium carbonate 1.95

Composite chapati or roti mixes can be developed using soybean flour

and sorghum flour in the proportion of 2:3. Sensory evaluation and con¬
sumer evaluation studies and consumer evaluation trials have shown high
acceptance for these roti mixes.

Table 15. Tested formulations of infant mixes

Infant mix Proportion

Sorghum soya mix

Sorghum rava: soybean flour: SMP 70:25:5

Sorghum soya mix

Sorghum flour: soybean flour: sugar 70:10:20

Sorghum pigeonpea mix

Sorghum flour: pigeonpea flour 80:20

Pearl millet pulse mix

Pearl millet flour: greengram flour 70:30

Pearl millet flour: blackgram flour 70:30

Pearl millet flour: Bengalgram flour 70:30

125
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Infant and weaning foods

Second category of food products as infant mixes using millets and leg¬
umes can also be developed. Some of the formulations which were tested
are given in Table 15.

Dehydrated foods
Usually papads are prepared with cereal and pulse combination. But
papads can also be prepared with dehulled sorghum flour. Processing, prepa¬
ration of sorghum, papads is shown in Fig.20.

Fig. 20. Preparation of sorghum papad

126
 CEREALS AND MILLETS

Breakfast foods
Fermented batter products are popular breakfast items in India. Among
these, items like dosa, idli, uthappam are very popular in Sourth India and
dhokla in North India. Rice and blackgram (Phaseolus mungo) dhal are the
major ingredients used for idli, dosa and uthappam. The proportion of rice
to dhal is usually 2:1 for idli, dosa and uthappam and 1:1 for dhokla.
Part of rice can be replaced/ substituted by sorghum semolina or flour
in the breakfast foods.

Snack foods
Deep fried foods are popular snacks in India in rural as well as urban
sector. They have good shelf-life.
Normally rice is the chief ingredient in the snacks. Dehulled sorghum
flour can be partly substituted in snacks (Vimala et al, 1990).

Baked food
Products like biscuits can also be prepared using dehulled sorghum
flour.
Dehulled sorghum and maize can be flaked. In this process sorghum
grains are pearled in a polishing machine. This pearled sorghum is wetted,
steamed under pressure and then flaked in a roller flaker.The flakes thus
prepared makes an excellent snack food.

MAIZE

Maize or corn (Zea mays) is utilized in more diversified ways than any other
cereal. With its high percentage of carbohydrate, lipid and protein, it is nutritous
for human consumption. A high percentage of maize grown in developing coun¬
tries is used for food and in India it is 80-90%. The ready-to-eat breakfast ceareal
cornflakes is a maize product. Maize is used in manufacture of feeds and for
manufacture of starch, dextrin syrup, industrial alcohol and alcoholic bever¬
ages. Corn also finds a number of other uses.

Varieties of maize
The principal maize varieties are flint corn, dent corn, sweet corn, pop¬
corn, flour corn and waxy corn. The classification is based on the nature
and distribution of starch in the endosperm.
Flint corn: Flint corn has very hard kernels. The texture is due to a rather
thick layer of hard starch and protein just under the bran layer. Flints
mature early. In India, mostly flint and semi-flint varieties are grown.
Dent corn: This has hard starch at the sides, while the major part of the
endosperm contains soft starch. At maturity a typical dent-like depression
appears at the crown. Dent comprises the largest maize corn in the United
States.

1271
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Sweet corn: The corn has a large proportion of carbohydrates of the ker¬
nel as dextrin and sugar in the unripe kernels which are tender. When
mature and dried, the kernels are hard and have a wrinkled surface. Prac¬
tically all canned corn is sweet. A small amount of sweet corn is dehydrated
or frozen.
Popcorn: A major part of the endosperm comprises hard starch on all
sides, with a very small core of soft starch.When the corn is popped the
endosperm expands with the formation of a fluffy white irregular mass. The
thick outer layers of the corn remain attached to the puffed endosperm in
an unexpanded form.
Flour corn: The grains are large and soft and the endosperm is very
friable.These characteristics permit easy grinding of the grain into flour.
Waxy corn: This contains a high proportion of amylopectin. It is of indus¬
trial importance.
' /

Structure and composition

The grain of maize is much larger than those of other cereals.The basal
part is narrow and the appex broad. The scutellum of maize is large and
form 10-13% of the grain. The embryo, scutellum and endosperm are within
the pericarp and testa, which are fused to form a hull which corresponds to
the bran of other cereals. The hulls of maize are lost in threshing (Fig. 21).

Maize grains may be white, yellow or reddish. Its kernel, like the kernel
of other cereals, consists of three main parts, viz. hull or bran coat with high
fibre content, embryo rich in oil and starchy endosperm. The average com¬
position of Indian maize is moisture, 14.9; protein, 11.1; fat, 3.6; fibre, 2.7;

128;
 CEREALS AND MILLETS

other carbohydrates, 66.2, and minerals, 1.5%. Using hybrids, maize of

different composition can be obtained. Those with high protein and lysine
content are not good for milling.
Starch is the predominant carbodydrate of maize (66-74% on dry ba¬
sis). The amylose content is about 27%. High amylose corn contains 55-
80% amylose. High amylose corn is only partially gelatinized when a water
suspension is boiled. In waxy varieties of maize, almost 100% of the starch
is amylopectin. Lower saccharides present in the grain in small quantities
are glucose, fructose, sucrose and raffinose. Cellulose and hemicellulose
are the principal constituents of maize hulls.
The major lipids of maize oil are triglycerides. Phospholipids and
glycolipids are present in small quantities. About 84% of the total fat of
kernel is found in germ and 15% in endosperm. The triglycerides have a
high proportion of oleic and linoleic acids.

Maize shelling
The operation of separating grains from maize cobs is performed by a
machine known as maize shejjer. Two types of maize shellers are in use, i.e.
hand-operated and power-operated. Hand-operated maize sheller, rotary
type (Fig. 22) consists of crank, a small feed inlet, a heavy cost iron fly
wheel, bevel wheel, shelling disc with lugs and spring controlled tong, all
mounted on a frame. The cobs are fed one by one, shelling takes place in
between the long, bevel wheel and shelling disc (Nageswara Rao, 1997).

Hi©]
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Milling
Maize is milled by a dry or wet process. In both processes the germ is
separated from the grain to extract and recover germ oil. The germ oil is a
i valuable product, but if allowed to remain a constituent ol maize meal would
lead to the development of rancidity. After degermination, the dry milling
employs roller mills and the process is somewhat similar to wheat milling.
- Wet milling involves a steeping stage and complete disintegration of the
endosperm to recover starch and protein.
In dry milling, the object is to recover the maximum amount of grits
with the minimum amount of flour, with the least possible contamination oi
germ. The grains are cleaned and conditioned by addition of cold or hot
water or steam , which results in loosening and toughening of the germ and
bran (Fig. 23).

Cleaning shelled corn

> f

Tempering

Impact cracking

Germ removal

> f

Grinding

> f

Sieving

Corn flour Corn meal Grits

Fig. 23. Corn processing

The endosperm is moistened to an ideal moisture content such that the

yield of grits is maximum. The conditioned grain is passed through a suit¬
able machine to separate the bran and germ. The stock after degermination
is dried to 15-15.5% moisture content and then sifted, to produce a number
of fractions. The large, medium and fine fractions (hominy) are then milled
in roller mills. This consists of a number of stages. All the finished grits,
meal (corn meal is a product somewhat smaller than grits, but still much
coarser than corn flour) and flour are sifted. The yield of products in dry

130
 CEREALS AND MILLETS

maize milling is generally grits, 40; coarse meal, 20; fine meal, 10; flour, 5;
germ, 14; and hominy feed 11%.
In India, maize is ground for wholemeal flour (atta) in power-driven or
hand-operated grinding stone or chakkis. The meal is sifted to remove fibre.
In large-scale milling, refined flour or maida and semolina or suji are pro¬
duced. Grits are used in the preparation of porridge to make corn flake, as
a brewing adjunct and to manufacture glucose by hydrolysis. Oil is extracted
from germ, while bran and germ meal are utilized as animal feed.
Maize is wet milled to obtain starch, oil, cattle feed and the products of
starch hydrolysis, viz. liquid and solid glucose and syrup. The first step in
wet milling is steeping. Clean maize is steeped for 48 hr in warm water
(50°C). Steeping in water softens the kernel and assists separation of the
hull, germ and fibre from each other. After steeping, the steep water is
drained off, and the maize is coarsely ground in degerminating mills to free
the germ from the gram. Then the ground material flows down separating
troughs in which hulls and grits settle, while the germ overflows. The germ
is then separated, dried and oil extracted by hydraulic pressing or by using
a solvent. The degerminated material in the separating troughs is then finely
ground in bhur or attrition mill. The hulls and fibre, which are not reduced
so much in size, can then be separated from the protein and starch by
sieving. The suspension of starch and protein from wet screening is ad¬
justed to a specific gravity of 1.04 by dewatering over string filters and the
starch is separated from the protein by continous centrifugation. Finally,
the starch is filtered and dried. The protein in the steep water is recovered
by vacuum evaporation and dried as gluten feed for animal feeding.
The by-products of wet milling of maize have many uses. The steep
water from wet milling contains free amino acids, proteins, carbohydrates,
minerals and growth adjuncts. It is concentrated to about 50% of solids and
is used as a nutrient for the micro-organisms producing penicillin and other
antibiotics. Maize oil, rich in essential fatty acids, finds use as a salad oil. Its
high smoke point makes it suitable for use as a cooking oil. The protein
concentrates, maize bran and oil-cakes are used as animal feeds.
Maize oil is being used increasingly for cooking purposes. Waxy maize is
commonly used for frozen foods because it exhibits less syneresis (release of
liquid from the gel) during a freezing—infreezing cycle. Maize (corn) flour is
often used for cooking. Its advantage over the flour of other cereals is its
moderate peak viscosity and greater stability in gelatinization. Hence it is
useful for institutional feeding where soup or gravy may be kept hot for long
hours.

Maize products
Several maize products of commercial value such as maize meal,
degerminated maize meal, puffed corn and corn flakes are produced.
Whole maize meal: It is prepared by powdering the whole maize kernel.

131
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Fig. 24. Flaking of maize

Degermed maize meal: It is powdered and sieved. The flour is devoid of

germ and hence has a low B-vitamin content.
Puffed com: It is commonly consumed as a snack.
Corn [maize] flakes: The preparation of maize flakes is given in Fig. 24
(Vimala et al, 1990).
Corn flakes are made from grits and hence have low contents of
B-vitamins. The proteins are under damage due to heat processing and
have very low protein efficiency ratio.
Corn starch and syrups: The wet-milling process is used for the prepara¬
tion of corn starch and syrups. Wet-milling process consists of steeping,
germ separation, grinding and centrifuging the slurry to get starch and syrup.
The protein nutritional value of rice is superior to all other cereals, as
rice has the least amount of unavailable carbohydrate among cereals (8.3%).

T32!
 CEREALS AND MILLETS

Crude fibre in rice is only 0.2%. Pearl millet has the highest amount of
unavailable carbohydrate (20.3%) and crude fibre is also present up to 1.2%.
Though fibre has a high therapeutic value, its presence in large amounts in
cereals affects protein digestibility and availability (Anjum and Warker, 1991).
Jain et al. (1989) also reported that protein digestibility and energy avail¬
ability from cereals decrease with increase in dietary fibre. The high amount
of fibre in wheat (especially whole) and oats is the reason for low biological
value of these cereals.

NUTRIENT COMPOSITION

Surveys were carried out by the National Nutrition Monitoring Bureau (NNMB)
of the National Institute of Nutrition, over the past decade in rural and
urban areas of 10 states of the country, to study the pattern of food and
nutrient consumption. The important proteins in cereals (George Borgstrom,
1968) are given in Table 16.
Table 16. Important proteins in cereals

Cereal Prolamines Glutelins Globulins

Wheat Gliadin Glutenin *

*
Rice Gliadin Oryzenin
*
Maize(corn) Zein Traces
★ ★
Barley Hordein
* ★
Millets Panccin
Rye Gliadin Glutenin Endestin
*
Oats Evenin Evenalin

‘Minor

It can be seen that while the diet of middle income groups in urban
areas is fairly satisfactory, that of rural and slum dwellers are inadequate in
many respects. The intake of protective foods like pulses, leafy and other
vegetables, milk, fruits, fats and oils are quite low in the diets of the rural
and urban poor. Gopalan etal. (1969) also observed that among the poor in
India, women of child-bearing age take less than 2,000 calories and 44 g
protein. This diet does not improve much during pregnancy and lactation
and is clearly inadequate.

ENZYME INHIBITORS

Foods of vegetable origin contain numerous enzymes inhibitors. Although

the presence of enzyme inhibitors is not limited to leguminous seeds only
they are found in alfalfa, guar, cereals (wheat and rice) and in potatoes
(Ferrando, 1981).

133 i
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Table 17. Main mycotoxicoses currently known in man

Species Foods infected Toxins Principal symmptoms

and lesions caused

Aspergillus flavus Groundnut, soybean, Aflatoxins, Hepatomas

haricot bean, cereal milk aflatoxin
grain and by-products

Aspergillus ochraceus Cereal grain, coffee ham Ochratoxins

Claviceps purpurea Cereal grain and Ergotine.ergotoxine, Ergotism (numbness

(rye ergot) by-products ergotamine, of the extremities,
ergocristine, etc. convulsions, gangrene,
etc.)

Fusarium graminearum Cereal grain and Toxins of a complex Nausea, vomiting,

and F. tricintum by-products nature including oestrogenic action in pigs
zearalenone

Fusarium javanicum Potato Oedema of the lung in

cattle

Fusarium Cereal grain and Fusariogenin Alimentary toxic aleukia

sporotrichoides var. by-products, stone fruit
tricinctum

Peniciliium citroviride Rice Citreoviridin, Irritation of the skin and

and P. citrinum Citrinin mucous membrane,
toxicity to liver and
kidneys

Peniciliium cyclopium Maize Cyclopiazonic acid

Peniciliium expansum Apples, cider Patulin Carcinogenic, mutagenic

Peniciliium islandicum Rice Icelandicin, Hepatotoxic, degenera¬

icelanditoxin, tion of the liver and
rubroskyrin, hepatomas
erythroskyrin

Rhizopus nigricans Coconut (tempeh) Dizziness, convulsions,

cyanosis (attributed to the
consumption of tempeh
in Java)

Stachybotrys atra Vegetable debris, straw Not isolated very toxic Dermatitis, catarrhal
angina, leukopenia, action
via the respiratory tract

Trichotechium roseum Maize Trichotecin and others

134
 CEREALS AND MILLETS

The biological significance of these anti-enzymes is uncertain. Some

authors suggest they are a defence mechanism and a way of protecting
certain compounds and their specific structures by inhibiting the degrada¬
tion of the nitrogenous parts, which are of a protein nature. This hypothesis
of a protective role seems to be justified when one considers the fact that the
most active enzyme—inhibitors are found in parts containing the reproduc¬
tive elements of the egg or seed. Their level usually diminishes during the
course of germination.

Mycotoxicosis
Statistical evidence shows that the geographical areas in Asia where
there is a high incidence of primary liver cancer in man are those where it is
usual to eat yellow rice.
Aflatoxins seem to be the most powerful liver carcinogens currently
known. They are mainly metabolized by Aspergillus flavus and they are
found especially on the seeds of plants that grown in tropical climates.The
optimum condition for growth of the mould, is a relative humidity of 80% at
between 30° and 35°C. Therefore groundnut, which is usually grown under
these conditions, is so often affected. It would, however, be a mistake to
think that only groundnut seed can be contaminated.
A systematic search for aflatoxins, carried out on various samples col¬
lected in markets in Thailand, shows that although groundnut is the seed
most frequently contaminated, and maize, millet, wheat, barley, soybean
and pepper can also be affected. In the markets of Hong Kong haricot beans
are the most contaminated; rice is rarely contaminated. Aflatoxin has been
found in material collected during the post-mortem examination of Thai
children who died of acute encephalopathy with degeneration of the viscera.
In Uganda, an investigation following the death of a 15-year-old boy who
showed centrolobular necrosis of the liver. Two young members of the same
family had similar but less severe symptoms. The family store of cassava
was found to contain 1.7 mg/kg aflatoxins. Since it was not current practice
in Uganda to carry out post-mortem anatomical or pathological studies, it is
possible that the effect of the presence of aflatoxins on the mortality of the
inhabitants of these regoins may be greater than has been thought. It should
also be noted that, 2 toxin-producing strains of Aspergillus ochraceus have
been isolated in ham in the United States (Ferrando, 1981). Table 17 shows
the main mycotoxicoses currently known in man.

REFERENCES

Anjum, F.N. and Warker, C.E. 1991. Review on the significance of starch and protein to wheat
kernel hardness. Journal of the Science of Food and Agriculture 561: 1-13
Altrogg, L. 1957. News zun Damp Lkonditioners - Urig Die ruhle, 94: 558 Anonomy, 1965,
From wheat to flour. Wheat flour Institute, Chicago, USA.

135
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Desrosier, N.W. 1977. Elements of Food Technology, 176pp. AVI Publishing Co. Inc. West Port,
Connecticut.
FAO, Rome. Quarterly Bulletin of Statistics. 8: 3/4 [fide Shellenberger, J.A. 1965. Fifty years of
milling advances. Cereal Science Today 10: 260-62.
Ferrando, R. 1981. Traditional and Non Traditional Foods. FAO of the United Nations, Rome.
George Borgstrom. 1968. Principles of Food Science, Food Microbiology and Biochemistry, vol.2.
The Macmillan Co., New York; Collies-Macmillan Ltd, London.
Gopalan C., Balasubramaniam, S.C., Ramasastri, B.V. and Visweswara Rao, K. 1969 Diet
Status of India. National Institute of Nutrition, Hyderabad, Andhra Pradesh.
Hesseltine, C.W. 1979. Some important fermented foods of mid Asia, the middle East, and
Africa. Journal of American Oil Chemists Society 56: 367-74.
Hoseney, C.R. and Rogers, D.E. 1988 The formation and properties of wheat flour doughs.
Critical Reviews in Foods and Nutrition.
Jain, R., Mann, S.K. and Flora, C.K. 1989. Effect of fibre on protein quality and energy avail¬
ability. Journal of Food Science and Technology 266: 364-65.
Juliano, B.O. 1993. Rice in Human Nutrition. FAO Food and Nutrition Series No.26. Food and
Agriculture Organization, Rome.
Juliano, B.O. and Sakurai, J. 1985. Miscellaneous rice products, (in) Rice Chemistry and
Technology. Juliano, B.O. (Ed.), American Association of Cereal Chemists, St. Paul. MN,
USA.
Luh, B.S.1980. Rice Production and Utilization. AVI Publishing Co., West Port, Connecticut,
the USA.
Magnus Pyke. 1981. Food Science and Technology, pp.45, 62, 72. Edn 4. John Murray, London.
Muller, H.G. and Tobin, G 1980. Nutrition and Food Processing. AVI Publshing Co.
Nageswara Rao, P. 1997. Processing equipment for grains, (in) Proceedings of Short Course On
Recent Developments in Grain Processing, held at Hyderabad during 14-23 August, pp. 237.
Nelson, C.A. and Loving, H.J. 1963. Mill stream analysis. Cereal Science Today 8: 301.
Rao, D.G. 1997. Machinaiy and engineering applications in grain processing, (in) Proceedings
of Short Course on Recent Developments in Grain Processing, held at Hyderabad during
14-23 August.
Rahim, A., Prabhavathi, C., Haridas Rao, P. and Shurpolekar, S.R. 1976. Suitability of durum
wheats for semolina milling and vermicelli preparation. Journal of Food Science and Tech¬
nology 13: 249.
Ramakrishnan, S., and Venkat Rao, S. 1995. Nutritional Biochemistry. T.R.Publications.
Rao, M.V. 1995. Proceedings of the Seminar on Food Security Situational Analysis and Strate¬
gies for Future.
Sekhon, K.S. 1989 By-products of rice milling. Paper presented at Seminar on New Directions
for Irrigated Rice Farming, held at Agricultural College, Bapatla, Andhra Pradesh, during
28-30 January.
Shakunthala, M.N. and Shadaksharaswamy, M. 1987. Foods, Facts and Principles, 244 pp.
Wiley Eastern Limited, Bangalore, Karnataka.
Shellenberger, J.A. 1965 Fifty Years of Milling Advances. Cereal Science Today 10:260.
Shuey, W.C., Moneval, R.D. and D.Ck, J.W. 1977. Eighty per cent extraction flour by tail and
regrinding and redressing. Cereal Chemistry 54: 42.
Steinkraus, K.H. 1983. Handbook of Indigenous Fermented Foods. 671pp. Marcel Dekker,
Inc., New York.
Uma Reddy, M. and Jayasree, K. 1990. Technologies relevant to rice based products; Tech¬
nologies relevent to wheat based products: (in) Proceedings of Summer Institute on Appro¬
priate Food Processing. Technologies for Rural Development, held during 15 June to 4
July 1990 at Hyderabad, Andhra Pradesh.
Vimala, V., Kaur, Kanwaljit and Hymavathi, T.V. 1990. Processing of millets and scope in
diversification. Proceedings of Summer Institute on Appropriate Food Processing Technolo¬
gies for Rural Development, held during 15 June-5 July 1990, Hyderabad, Andhra Pradesh.
Yemazaki, W.T. and Andrews, L.C. 1981 Experimental milling of soft wheat cultivars and
breeding lines. Cereal Foods World 26: 580.

136
 CEREALS AND MILLETS

LEARNER’S EXERCISE

1. Name the cereals and millets found in common use. Explain their importance in our diet.
2. Explain food fortification and food enrichment with examples.
3. Explain the structure of a cereal grain with a diagram.
4. How can the nutritional quality of a cereal product be improved? Explain with examples.
5. What is parboiling and explain the processing.

137
12 Legumes

L egumes are second to cereals as an important source of human food.

Legumes are considered as meat of the vegetable world and are close to
animal flesh in protein food value. They are of world wide distribution and
every area has its local ‘pea’ or 'bean’. The fruit is a pod containing 2-10
seeds. As regards composition, there are basically 2 groups of legumes (Muller
and Tobin, 1980). First there is high-protein high-oil group. This comprises
soybean, groundnut, lupin and winged bean. These legumes are mainly
used for processing. Protein content is as high as 35% and oil content varies
from 15-45%. The second group comprises the moderate-protein low-oil
types. The representatives of this group are most important as human food.
Examples are the cowpea, gram, pea and lentil as well as the Phaseolus
group.

NUTRIENT COMPOSITION

Approximately 100 species of legumes are considered to be edible from among

the over 13,000 legume species found in the world. For 39 species of edible
legumes information is available on area and method of cultivation, chemi¬
cal composition and utilization.
The nutrient composition of edible legumes depends on the species. In
general, their protein content is high and is commonly more than twice that
of cereal grains, usually constituting about 20% of the dry weight of seeds.
The protein content of some legumes like soybean is as high as 40%. The
nutritional value of legumes is not just confined to their usefulness as a
source'of vegetable protein. They are rich in carbohydrate and some species
like groundnut and soybean are rich in oil. Legumes are also sources of
other nutritionally important materials such as vitamins and minerals.

Proteins
Legume proteins are chiefly globulins but albumins are also present in
a few species. Their nutritional importance depends not only on the quan¬
tity of protein but also on its quality which in turn depends on the amino
acid composition. Legume proteins are deficient in sulphur containing
aminoacids, particularly in methionine, and in tryptophan. All the pulses
contain sufficient amount of leucine and phenylalanine. Lysine and threonine
contents are low only in groundnuts (ICMR, 1984; FAO, 1973).

138
 LEGUMES

Carbohydrates
Legumes contain 55-60% of total carbohydrates including starch, solu¬
ble sugars, fibre and unavailable carbohydrates. Starch accounts for the
major proportion of carbohydrates in legumes. The unavailable sugars in
pulses include substantial levels of oligosaccharides of the raffinose family
of sugars (raffinose, stachyose and verbiscose), which are notoriously known
for the flatulence production in man and animals. These sugars escape
digestion, when they are ingested, due to lack of a-galactosidase activity in
the mammalian mucosa. Consequently, the oligosaccharides are not ab¬
sorbed into the blood and are digested by the microflora of the lower intes¬
tinal tract resulting in the production of large amounts of C02 and H2 and a
small amount of methane (ICMR, 1984; and FAO, 1973).

Lipids
Lipids form about 1.5% of dry matter in pulses except in groundnut,
soybean and winged bean. Most of the pulse lipids contain high amounts of
polyunsaturated acids. These undergo oxidative rancidity during storage,
resulting in a number of undesirable changes, such as loss of protein solu¬
bility, off-flavour development, and loss of nutritive quality.

Minerals
Legumes are important sources of calcium, magnesium, zinc, iron, po¬
tassium and phosphorus. A major portion (80%) of phosphorus in many
legumes is present as phytate phosphorus.

Vitamins
Legumes contain small amounts of carotene, the provitamin A. Many
legumes contain 50-300 iu of vitamin A. The thiamine content of legumes is
approximately equal to 0.4-0.5 mg/100 g. Legumes are also fairly rich in
niacin—about 2.0 mg/100 g. They are poor in riboflavin and dry legumes
are almost devoid of ascorbic acid (Shakuntala and Sadakesharaswamy,
1987).
Chemical composition of pulses per lOOg edible portion is given in
Table 18.

PROCESSING OF PULSES

Preparation of dhal from pulses is an important aspect in pulse processing.

Dhal milling is widely practised in Asia, Africa and South America.

Decortication
Dry whole grain legumes have a fibrous seed coat (husk or skin) which
often is indigestible and may not be palatable. In such cases the skin has to
be removed. A number of methods are available for decortication. A simple
method is to soak the seeds for a short time in water; the husk takes up

139
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

o
c CT) o o
E E
CO o o o
cd

z ^_
o CO CD O CO 1— LO CD 1
00
CD £ CM CM 'r~ T— CM c\i c\i
iz

c
>
C-—

0.18
CD LO O o CO C- o
3 CM CM 1— CM CM
r—
O E O O O o O CD
JD
cr

0.54
O CM 1— C\J h- CM CD
CO O’ LO LO O' O" CO
o O o O o o

CD

30
CO
CO
CO
C\J
t- O O'
CD

CM

6.7
cd r-~ CO O' CO
O CD LO CM h- CO CO

CO
CD
_C0
3 CM
T—
LO
T~
CO co

-
CL CD CO CM
CO CO O' CO CO CO
O
c
o
CO
o
O' r^~

137
CL CM O'
E O
CM
LO h- o
co CM co
CM
o
CD
o
o
15
o >
'E 2* cD O' ■>— LO
341
o r^- co
CD CD O CO O' CM O' CO CM o-
_C C ^ CO CO CO CO CO CO co
O LU
CO

a> 6. <*>
®
■9CD -o
61.4

CD CO LO T— h- CM CO
JD
CD 2 a> O CD O' o cd cd
CO LO LO CO LO LO LO
I— o ^
o
4.2

CD CD CO O' T“ CO CO
.g
CO O CO 1 •o LO CM
Ll
3.8

O CM CM CM LO CM CO
CO CO CO CO cd cd CM
1.7

CO O; O CO co LO CO
LO 1 O T~ o o

,_ o _
CD o o CM
22.1

r- O' ■O’ •O' O' CM oo

T- CM CM CM CM CM CM

o
11.0

CD O' O' co
co
9.6

(Phaseolus vulgaris)

CO
CD cd o cd CD>
■+-—
CO 3 cd
CD to
( " 1 TO T~ CO 1 CO
c -Q 3
E 3 3 CD "Cl i-_
>
O O
E -Q 2
Kidney bean

E Ji 3 15 TO
2 .2 p
l_
CD
775
CD -2 E CO E
5 JZ CO
CD c c co CD 23 CD CO ~u CO
b> co o CD 3 CD o
CD -C
O
CD CD
k_ O 3
c L-
CD ^ O) CD CD v'j CD -C
CD CO CL (—■ JO o cz CO CD o CD
*— CO £
_CO g>8 o CD
CD
$ CD
TO CD CD
<d
CO
o CD
3 O s
CD b -C TO
£ s cE Q
CL CD O LL O X

140
 LEGUMES

03
o c
c o
■4—'
O)
E £
CM O CT3
eg
"O
i> 03

c
o CD
03 £
CO
CM
LO
1 CO
03
C\i
CM
CO
O
c
g
c to
>
N
_ro a
O) O 03 03 03 03 co
CM O T— T— CO 03
o E
.g CD C3 C3 o o 6
be 03
O
03
3
g
c
LO LO h- LO
■O'
CD CO 03
'E ”sf ■M" 'O' h- <
03 E X3
o CD
C
co
TD
CD O
C o
03
03 O 03 CM co c
O c- 03 CO CO CM o
CO CM "vf
O

c
c
CD LO CD LO co
o 00 E
E ■M- 03 LO LO 30
I
03 C
=3 03
i_
O 03
sz CD CO O CO ■O' o E
TO
Cl 03 CO 03 o 03
03 E CM CM CM CO CO 03
03
o -J
CO
1^
CD
E
2 O
CD 03 CM LO CO O
o
E O h- <
CO
CO CM r^- CM U_
O g”
T3
_c
>
03 03 CO o LO LO CM ■o'
T- 03
03 O 'cr CO CO CO _Q
CZ 3^ co CO CO CO •M" CD
LU CD
"O
, C/3 I
6 £ o LO LO CO 03 DC
_Q CO
03 03 CO co CD
CO "D LO LO LO LO CM O

03
TO
L_ 1^- LO LO LO r>- GO
_Q O)
o 'J- CO "O
T— o
.o
_co c
g
CO
LO CM LO eg XD
CD 03 JC
C CM CO CM CO '}■
o
03
_ro
CD
LO >
CO 03
o
03 03
>
E
03
33
C
03
CO CO CM ^ CT3 ■M"
03 CO CM CM
■O'
LO 03 CX3
O C\J CM CM 03
cl co c is
33 5 c
ti CO
O -9 o CD
CD 3^ C3
TO
TO ' 03 CD
CD
d
00 o O "O' __ .O) s co C
-o to 03 CM o ^ CO CO CO
o c JTO
_D o cB 03 03
Q_
O c D*
i
o c O
o 1. E
£= .03 -Q CD
O vZ TO .CO 'D cu >
o CO
CO i> TO- TO s
c c
o o 03
c 03
J2 CO o E TO d c P CO
o6 co CD CO
cz > >. TO ^
03
Z3
o o CL 33 CO
CD
Q
00 CO 03
c C c ■k ¥
¥ +
o 03 03 _ w
03
E o .CO CD
o
_Q TO D 03
co
_03
cz
C
CD
£ jS CO 03
CD
03 co'
>. E
=3 o CD o
Q_
03
b_
O
CO cc
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

more water than the seeds and may be easily separated by rubbing while
still moist. In the alternative, the soaked grains may be dried and the husk
removed by pounding and winnowing. Roasting also renders separate husk
easily. Roasted legumes like those of Bengal gram and pea are widely used
in India.

Milling
Milling of pulses is achieved by 2 stages—loosening of husk and its
removal followed by splitting into dhal. Loosening of the husk is achieved by
intermittent sun-drying after application of oil and water. Dehusking and
splitting is done in chakkis or power driven machines. There is much loss
due to powdering and/or breakage in this process (Raghavendra Rao et al,
1989). This process, dependent on climatic conditions, is laborious, and
does not give more than 70% of dehusked grains although higher yields are
possible.
The methods used for dehusking the legumes are: wet process, and dry
process. In the former skin conditioning is done with water, whereas in
latter skin conditioning is done with oil. Improved dhal milling process, is
also used for dehusking.
Wet process: The wet process has been specially used for dehusking
pigeonpea, as the skin of pigeonpea is difficult to remove. The process con¬
sists of (a) soaking the grain in water overnight, (b) smearing the soaked
grain with red earth mixed with water and keeping the grain moist as a
heap by sprinkling water for 16-24 hr, (c) drying the grain under the sun,
and (d) dehusking the grain using granite or wooden hullers.
Dry process (conditioning with water): This process is suitable to legumes
such as chickpea, lentil, lathyrus, pea and dried pea. The grains are cleaned
sprayed with water 5-10% by weight of the grain and kept in a closed vessel
for the water to be fully absorbed by the skin. The material is then dried
under the sun. The dried legume is passed through a roller mill. About 70-
80% of grains are dehusked and split simultaneously.
Dry process (conditioning with oil): This method is applicable to pigeon-pea
or blackgram and greengram, as the skin in these legumes strongly adheres
to the endosperm. The grains are passed through the roller mill for pitting
the skin. Vegetable oil (about 1-2%) is applied to the skin. In greengram,
grains are coated with oil straight away without preliminary pitting. The
grains are dried under the sun and then conditioned by spraying water
(about 4-5%). The conditioned grains are again dried under the sun and
dehusked using roller mill or Engelberg type of rice huller.
Improved dhal milling process: This process has been developed by the Cen¬
tral Food Technological Research Institute (CFTRI), Mysore. The process
begins with conditioning with water in a special conditioning equipment to
loosen the husk, and dehusking by means of specially designed dehulling
equipment. The yield of dehusked split legume (dhal) is 80-85% by the

142
 LEGUMES

improved process compared with 60-70% by the conventional process

(Swaminathan, 1987).
Improved technology and machinery have, therefore, been developed to
eliminate these defects of traditional processing and facilitate the milling
operations throughout the year, independent of climatic conditions. In this,
the size-graded pulse is conditioned by heating in a current of hot air in a
vertical counter-current through flow drier and tempering in specially de¬
signed bins for slow aeration and loss of moisture. The heating and temper¬
ing are done to bring the grains to the critical moisture level to loosen the
husk. The conditioned grain is then dehusked in an abrassion type pearling
machine. Dehusked pulse is split, to obtain dhals in an impact mill after
moist conditioning. The yield of dhal is 7-10% more than in traditional method
and time required for processing is less than a day.
This process, originally developed for pigeonpea or redgram (Cajartus
cajan) pulse, has been suitably adapted to other pulses such as Bengal
gram, blackgram, greengram, lentil, pea, khesari, horsegram, kidney bean,
cowpea, soybean, winged bean and lupins. By this new method, yield of
dhal is 81-85% compared to the traditional ones with 65-76% yields.
Recently, pulse dehusking machine has been developed at the CFTRI
for small scale processing requirements. Hand operated vertical cone pol¬
isher was found to handle 10 kg pulse/hr. Conditioned tur and Bengal gram
gave 72% and 80% yield respectively. This machine is now available in pow¬
der driven mode. Hand operated version of under runner disc type machine
is reported to handle about 20 kg pulse/hr.

Dhal
Making Dhal (split legumes without husk) from legumes is a speciality
of the Indian subcontinent. Methods of improving palatability and suitabil¬
ity for versatile use and reducing the cooking time of pulses have been
worked out. Even the commercial methods in vogue followed a similar pro¬
cedure. A dry conditioning technique for drying of the pulse to a low critical
moisture level for thorough loosening of the skin has been developed at the
CFTRI. Details of drying and milling procedures appropriate to all legumes
have been worked out. Even difficult-to-mill legumes such as horse gram,
fieldbean, gurbean etc. can be processed by these procedures. Milling meth¬
odology and machinery for each pulse have also been standardized. These
procedures although efficient and hygienic have not found wide commercial
application because of economic and investment considerations. A combi¬
nation of modern dry conditioning procedure coupled with existing or slightly
modified milling machinery may be advantageous in the popularization of
new technology.
Another feature in the Indian subcontinent is the low level of use of ,
soybean as an edible pulse. Although nearly 1 million tonnes are produced,
only a small fraction is used for edible purposes. After extraction of the oil,

143
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

the meal is almost all exported for feed purposes. In view of the existing
pulse shortage, all available soybean should be used for edible purposes as
an extender or supplement to the indigenous pulses. Although soybean dhal
cannot be easily cooked to a soft textured dhal, processed soya flour had
great potential for making all the popular sweet and savoury snacks nor¬
mally made from Bengal gram flour. Soya dhal could be used for making
fermented products like idli and dosa.
Puffed legumes are cheap and popular food for the common man. The
flavour and light texture of the product make for its popularity. Puffing is
effected by manual or mechanical roasting of conditioned legume in hot
sand. The puffing expansion during roasting is maximum in Bengal gram
which is most popular for puffing. Pea and greengram are also used to a
small extent for puffing. Why some pulses puff better than others needs
investigation. It is possible that, apart from other things, hydration of the
cotyledon to some extent may be necessary to cause high volume of steam
causing volume expansion during puffing. The hydration property of the
skin which affects wetting of the cotyledon may also be a factor. These as¬
pects need to be looked into for getting better-quality puffed products.
Sprouted legumes are also occasionally used traditional legume foods.
Sprouting causes partial breakdown of starch and proteins and contributes
to better digestibility. The special flavour associated with sprouted legumes
is an added advantage. Popularization of the sprouting practice and using
more of sprouted legume is called for. It could also be sold as a ready-to-use
marketable product. Sprouting causes hydrolysis of the oligosaccharides
also responsible for causing flatulence of legumes. Conditions of sprouting
of various legumes need to be standardised.

Convenience foods
Apart from staple dishes, many other dishes and adjuncts which are
used as snacks or for increasing the taste appeal of the main staple food.
The traditional methods of making these dishes involve either too much
time, skill or drudgery which seem to be not compatible with the busy world
of today. Hence the need for time and labour saving convenience foods for
the modern man who feels he can afford to pay for the cost of providing such
convenience. Convenience foods of ready-to-eat type have been developed
using legumes.
Papad: Legume-based wafer or papad is yet another important commodity.
Papad made from dhal flour dough, is a widely consumed product in India.
The traditional method of making is by rolling the dough with a rolling pin.
A leg-operated papad press produces 500 papads/hr, in comparison, a con¬
ventional screw press produces only 150 papads/ hr and manual operation
about 120 hour (all per 2 persons). A table model hand-operated papad
press for making papad or chapati at house-hold level is developed. About
120 papads or 200 chapatis can be made per hour using this machine.

144
 LEGUMES

Cereal-pulse mixes: The customary commercial brand of weaning foods

based on roller drying or extrusion cooking of cereal-pulse mixes are natu¬
rally too costly for people in the middle-and low-income groups of the popu¬
lation. Work has recently been carried out on a new category of weaning
foods which would be substantially cheap, which could be made on a small
or large scale in the household or small factory using locally available mate¬
rials and based on popular household technologies like malting, puffing,
chapati making, vermicelli extrusion, flaking etc. Depending on local re¬
quirements, any of these simple processing can be adopted to make wean¬
ing foods for household or small scale commercial use. Their nutritive value,
taste appeal and freedom from side effects have been demonstrated by feed¬
ing studies on young children. The addition of malt to the weaning foods
can decrease paste viscosity and increase caloric density and make for greater
intake of nutrients per feed of the child.

Quick cooking pulses

Many pulses are required to be cooked soft for consumption. The cook¬
ing time needed for softening is long (15-45 min). Reduction of cooking time
can be effected in a pressure cooker in many cases. Instant or quick cooking
pulses is a necessity for modern urban consumers and for special defence
needs for whom time saving is important. Precooked rice, dhal or suji dried
under special conditions to induce a porous texture making for short hydra¬
tion time are becoming necessary. Appropriate technology for dhal devel¬
oped in the laboratory may shortly become commercial propositions.
Pulverizing grains of grain mixes and reshaping into original form would
also substantially reduce cooking time.

Puffing
Pea and Bengal gram are commonly puffed. Moist conditioning before
roasting helps in good puffing. Continuous gram roasters are in commercial
use for puffing. The roasted grains get dehusked, puffed and split as they
are subjected to mild impact between a knurled roller and a hot plate. Ex¬
pansion during puffing varies with variety and process conditions and range
from 1.2 to 2 times.
Manually operated puffing machine developed by Suryanath and
Srivastava (1982) was modified for uniform heat transfer and smooth dis¬
charge of sand and puffed grain. It’s capacity is to produce about 50-60 kg
puffed grain per day (Jain and Bal, 1989). Puffing machine (Fig. 25) consists
of a mild steel cylindrical container with concave bottom to facilitate positive
discharge.

Antinutritional factors
The factors that limit the full utilization of food legumes include prolonged
cooking time, deficiency of sulphur, amino acids, low protein digestibility

145
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

and the presence of various antinutritional factors like protease inhibitors,

haemagglutinins, phytates, flatus factors, tannins, etc.
Protease inhibitors: Substances which have the ability to inhibit the
proteolytic activity of certain enzymes are found throughout the plant king¬
dom, particularly among the legumes. The inhibitors suppress the release
of amino acids and thus do not make for the normal growth of animals fed
with such legumes. Trypsin inhibitors are found in a large number of leg¬
umes including soybean, peanut, navy bean, lima bean, etc. (Liener, 1973).

Phytohaemagglutinins
Another substance which appears to be universally distributed among
the legumes is a protein which has the unique property of being able to
agglutinate red blood cells, the so-called phytohaemagglutinins.

Goitrogens
Among the legumes, however, only the soybeans and peanut produce
goitrogenic effects in animals. The goitrogenic principle identified in ground¬
nut is a phenolic glycoside which resides in the skin. It was suggested that
the phenolic metabolites formed from this glycoside are preferentially
iodinated and thereby deprive the thyroid of available iodine. Thus, the
goitrogenic effect of groundnut is effectively counteracted by iodine supple¬
mentation.

146
 LEGUMES

Cyanogens: Legumes predominate in terms of their cyanide-producing

potential. Cases of human intoxication (cyanide poisoning) from the con¬
sumption of certain varieties of lima bean are not uncommon today in some
of the tropical countries. Cyanide in the form of HCN (hydrogen cyanide) is
released from a glycoside through the action of an enzyme p-glycosidase
present in the plant tissue (Liener, 1969).
Anti-vitamin factors: The inclusion of unheated soybean-meal or the protein
isolated therefrom, in the diet of chicks may cause rickets unless higher
than normal levels of vitamin D3 are added to the diet. Raw kidney beans
perhaps contain an antagonist of vitamin E as evident from liver necrosis in
rats and muscular dystrophy and low levels of plasma tocopherols in chicks.
Soyflour was said to contain antivitamin B]2 factor.
Metal binding constituents: Isolated soybean protein decreases the avail¬
ability of certain trace minerals such as zinc, manganese, copper and iron.
Pea also contain a factor which interferes with the availability of zinc for
chicks.
Lathyrogens: Lathyrism is a disease. Consumption of certain species of
pea belonging to the genus Lathyrus causes lathyrism. The lathyrogen of
the sweet pea was isolated and identified as B-(N a-glutamyl) amino
propionitrile. A compound, which may very well be the causative principle
of human neurolathyrism was identified as B-N-oxalyl ct-p diaminopropio-
nic acid. Its injection in young chicks, rats and monkeys produced severe
neurotoxic symptoms.
Favism: Favism is a disease characterized by haemolytic anemia which
affects certain individuals following the ingestion of fresh raw or cooked
broad beans. The red blood cells of individuals who are prone to favism
show a number of biochemical abnormalities, the most significant of which
are diminished levels of reduced glutathione and glucose-6-phosphate
dehydrogenase activity (Liener, 1980).

Methods of elimination of antinutritional factors

Soaking, heating and fermentation can reduce or eliminate most of the
toxic factors of the pulses. Correct application of heat in cooking legumes
can eliminate most toxic factors without impairment of nutritional value.
Cooking also contributes to legume digestibility. Heat causes denaturation
of the proteins responsible for trypsin inhibition, haemagglutination and
the enzyme responsible for the hydrolysis of cyanogenic glycosides. The mode
of application of heat is important. Autoclaving and soaking followed by
heating are effective. Another way of eliminating toxic factors is fermenta¬
tion, which yields products more digestible and of higher nutritive value
than the raw pulses (Shakunthala and Shadaksharaswamy, 1987).

Processing
Processing of pulses is important in improving their nutritive value. The

147
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

processing methods used are soaking, germination, decortication, cooking

and fermentation.

Soaking
Soaking in water is the first step in most methods of preparing pulses
for consumption. As indicated above, soaking reduces the oligosaccharides
of the raffinose family. Soaking also reduces the amount of phytic acid in
pulses.

Germination
Germination improves the nutritive value of food pulses. The ascorbic
acid content of pulses increases manifold 48 hr after germination- Germi¬
nated and sprouted pulses are being used to prevent and cure scurvy since
the 18th century. The riboflavin, niacin, choline and biotin contents of all
pulses increase during germination.

Fermentation
The processing of food pulses by fermentation increases their digestibil¬
ity, palatability and nutritive value. Soybean is a very valuable pulse whose
proteins approach the quality of animal protein. However, it cannot be di¬
rectly used as food because of the toxic substances present in the pulse.
The toxic substances can be eliminated by fermentation. In South-East Asia
various fermented products of soybean are produced and consumed on a
large scale. It appears to be possible to prepare products from Bengal gram
similar to those of fermented soybean products. The common example of
fermentated product is idli (blend of fermented blackgram and rice). This
fermentation process improves the availability of essential amino acids and,
thus, the nutritional quality of protein of the blend. In general, the nutritive
value of the legume-based fermented foods is to be higher than their raw
counterparts.

Flaking
Soybean flaking machine (Fig. 26) consists of 3 rollers with 1 hp electric
motor. The differential speed is maintained by a set of gears. The processed
soya dhal at 25-30% moisture content on wet basis is prepared and stretched
in between rollers to get flakes (Krishna Kumari, 1997).
Soy flakes will be another popular dietary item which falls within the
existing food habits. A single process was developed for making soya flakes
at rural level (Krishna Kumari, 1990) is given in Fig. 27.
Similarly, fruits cereal flakes and vegetable cereal flakes also can be
prepared. Cereal vegetable and cereal fruit flakes also can be prepared in
the similar manner.

148
 LEGUMES

Fig.27. Flaking of soybean

149
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

INDUSTRIAL BY-PRODUCTS

Protein concentrates
Products containing a minimum of 70% protein are termed protein con¬
centrates. These are prepared from defatted soybean flakes or flours by
removing water-soluble sugars, ash and other minor constituents including
compounds giving raw soybean, and bitter flavours (Desrosier, 1977). Con¬
centrates consist of the major proteins plus the polysaccharides. They are
made by the methods that insolubilize the proteins, while the low-molecular
compounds are removed. One process consists of extraction with aqueous
alcohol whereas second involves extraction with dilute acid at pH 4.5
(isoelectric point and region of insolubility of major proteins). The acid-leached
concentrate is neutralized before drying. In a third process the proteins are
insolubilized by heat denaturing. The low-molecule weight constituents are
then washed out with water. Three types of concentrates are similar in
chemical composition but differ mainly in water solubility of protein. The
acid-leached products are extensively denatured and insoluble.

Isolates
They are prepared by removing all water-insoluble polysaccharides, as
well as water-soluble sugars and other minor constituents from soya flakes
or flour. Defatted flakes or flours of high protein solubility are extracted
with dilute alkali (pH 7.9) at 50°-55°C. After the insoluble residue (water
insoluble polysaccharides plus residual protein) is separated by screening,
filtering and centrifuging, the extract is adjusted to pH 4.5 with food grade
acid, where the major proteins are brought to their isoelectric point, they
precipitate.
This protein curd is filtered or centrifuged (Dessosier, 1977) from the
solubles (soya whey) and washed. The curd may be spray dried to yield the
isoelectric form of the protein, but more commonly, it is neutralized and
spray dried to give the proteinate form, which is water-dispensible, sodium
proteinates are the major types sold although potassium and calcium
proteinates are also manufactured.
Composition and properties of commercial protein isolates are gener¬
ally typified by their low pH, low ash and insolubility in water. Although
protein contents of commercial isolates may be similar, their physical prop¬
erties, including solubility and molecular weight distribution, can be appre¬
ciably different when similar types are compared because processing varies
between manufacturers.

REFERENCES

Desrosier, N.W. 1977. Elements of Food Technology. AVI Publishing Co., Inc., Westport, Con¬
necticut.

150
 LEGUMES

FAO. 1973. Legumes in Human Nutrition, Food and Agriculture Organization of the United
Nations, Rome.
FAO. 1995. Quality bulletin of Statistics. Vol.8 3/4.
Gopalan, C., Romesastry, B.V. and Balasubramanian, S.C. 1984 Nutritive Value of Indian
Food Stuffs, pp. 26-56. Indian Council of Medical Research; National Institute of Nutri¬
tion, Hyderabad, India.
Jain, R.K. and Bal, S. 1989. Grain Puffing Machine. Bulletin, PostHarvest Technology Centre,
Indian Institute of Technology, IGiaragpur, West Bengal.
Krishna Kumari, K. 1997. Simple technologies for making soya products, (in) Proceedings of
Short Course on Recent Developments in Grain Storage. ANGRAU, Hyderabad.
Krishna Kumari, K. 1990. Processing of soybean — technological implications. Proceedings of
Summer Institute on Appropriate Food Processing Technologies for Rural Development, held
at Hyderabad, 15th June to 4th July.
Liener, I.Er 1969. Toxic Constituents of Plant Food Stuffs, edn 2., 283 pp. Academic Press, New
York.
Liener, I.E. 1966. World Protein Resources, Advances in Chemistiy, Series 57, American Chemi¬
cal Society Publication, Washington.
Liener, I.E. 1980. Protein Nutritional Quality of Foods and Feeds, New Protein Foods, AVI Pub¬
lication Co., Inc., West Port, Connecticut.
Muller, H.G. and Tobin, G. 1980. Nutrition and Food Processing, pp. 146-148; 151-153, AVI
Publishing Co., Inc., Westport, Connecticut.
Raghavendra Rao, M.R., Chandrasekhara, N. and Ranganath, K.A. 1989. Trends in Food
Science and Technology, (in) Proceedings of the Second International Food Convention
(IFCON-88), held during 18-23 February 1988 at Mysore.
Shakunthala, M, N. and Shadaksharaswamy, M. 1987. Foods : Facts and Principles. New Age
International Pvt. Ltd, New Delhi.
Suryanath and Shrivastava, S.H. 1982. Hand operated Puffing machine. A boon to rural
artisans in India. Paper No. PEF 129. Presented in the 20th Annual Convention of ISA,
held at Pantnagar, Uttar Pradesh.
Swaminathan, M. 1987. Food Science, Chemistry and Experimental Foods. The Bangalore Print¬
ing and Publishing Co. Ltd., Bangalore, Karnataka.

LEARNER’S EXERCISE

1. Explain the nutritional contributions of pulses in the diet.

2. How are legumes processed and used in diet?
3. What are the antinutritional factors found in legumes and how to eliminate the same?
4. Explain the effect of antinutritional factors on the health.

151
13. Nuts and
oilseeds

N uts and oilseeds are in general rich sources of proteins, with the excep¬
tion of coconut and of fat. Oilseeds are the major sources of edible oil.
Edible oilseed meals obtained from oilseeds are rich in proteins and have
been used for the preparation of infant foods and protein foods for feeding
infants and preschool children in developing countries. The major oilseeds
produced in the country include groundnut, rapeseed and mustard,
castorseed, sesame, nigerseed, linseed, safflower, sunflower and soybean.
However, groundnut, rapeseed/mustard and soybean account for a major
chunk of the output. The 16 states, Andhra Pradesh, Assam, Bihar, Gujarat,
Haryana, Himachal Pradesh, Jammu and Kashmir, Karnataka, Kerala,
Madhya Pradesh, Maharashtra, Orissa, Punjab, Rajasthan, Tamil Nadu,
Uttar Pradesh and West Bengal account for 99.2% of the area and 99.4% of
the output of oilseeds in the country.
The country has about 1.332 million ghanis, 25,000 oil mills equipped
with small expellers and crushers, over 600 solvent extraction plants, 300
vegetable oil refineries and 175 hydrogenation plants. The crushing/expel¬
ling of seeds and production of mustard oil, groundnut oil and sesame oil is
reserved for the small-scale sector. The large-scale sector, however, is al¬
lowed to pack and market these oils under their own brand names. Production
of widely grown nuts and oilseeds is given in Table 19 (FAO, 2000).

Table 19. Production of nuts and oilseeds ('000 tonnes) during 2000

World Asia India

Groundnut in shell 28,408 20,153 8,200

Soybean 126,957 20,812 6,840
Sunflower seed 24,490 3,987 810
Rapeseed 31,958 13,413 5,670
Cowpea 15,613 12,618 4,300
Cotton seed 1,465 145 1,100

Oil is obtained commercially from quite a number of plant sources.

Sometimes the oil is a by product, e.g. as with maize, and at other times the
oil is the main product (e.g. sunflower). Important sources of plant oils with
their percentage oil content (at natural moisture content) are given Tables
20 and 21.

152
 NUTS AND OILSEEDS

Table 20. Important sources of plant oils (natural moisture content)

Plant source % Plant %

Maize 5-10 Olive 15

Groundnut 40-45 Sesame 45-50
Soybean 15 Sunflower 30-40
Cotton seed 20-25 Oil palm 45
Linseed 35 Coconut flesh 65
Rapeseed 35-40 Castor bean 45-50

Table 21. Analytical data of some plant oils

Plant oil Specific gravity Refractive index Iodine value Saponification value
(15.5°C) (40°C)

Palm oil 0.858 1.451-1.459 49-57 196-202

Palm kernel oil 0.859-0.871 1.449-1.451 14-19 245-250
Olive oil 0.915-0.918 1.4605-1.4635 78-88 190-195
Coconut oil 0.869-0.874 1.448-1.450 7.5-9.5 255-260
Groundnut oil 0.917-0.919 1.4625-1.4645 85-100 100-196
Soybean oil 0.924-0.928 1.473-1.477* 129-139 190-194
Cotton seed oil 0.920-0.925 1.4645-1.4655 103-115 190-198

*At 20°C

STRUCTURE AND NUTRIENT COMPOSITION

Oil palm
The oil palm (Elaeis guineensis) is the world’s most important source of
oil for food and soap manufacutre. The plant has a higher oil yield per
hectare than any other. The plant favours a tropical climate with relatively
high rainfall. Female and male flowers occur on the same tree and the female
inflorescence produces a bunch of about 200 fruits. There are about 2-6
bunches on each tree per annum. Fruit of the oil palm (L) and a transverse
section of 1 nut (R) are shown in Fig.28.
The fruit, about 4 cm in length, is covered by a skin with the oil-bearing
fibrous pulp below. This in turn contains a hard and fibrous shell or 'nut'
which is often used locally as fuel. Inside this shell the palm kernel is found.
The oil of the outer fibrous pulp is referred to as palm oil and that of the
palm kernel as palm-kernel oil. The proportion of these 2 oils depends on
the species. Extraction is traditionally by pressing. Palm oil may contain a
fair amount of p-carotene (provitamin A).

Olive
Though olive (Olea europaea) is of Mediterranean origin, today it grows
also extensively in California, China and South Australia. The fruit is like a

153
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Fig. 28. Oil palm. L, Fruit of the oil palm; R, transverse section of a nut

small plum, green and dark purple when ripe, containing 1 hard seed. For
use the flesh containing the oil is expressed mechanically.

Coconut
The coconut palm (Cocos nucifera) is grown in tropical lowlands of Asia
and to some extent in America and Africa. The trees are about 25 m high
and bear coconuts in bunches. Each nut has a hard shell with a layer of
white meat on the inside. When unripe the nut contains coconut milk—a
pale whitish liquid with a strong taste of coconut. This liquid is gradually
absorbed as the nuts ripen. The coconut meat is either sun-dried or kiln-
dried and is known as copra. Its oil content is very high, of the order of
60-65%.
Dehydrated coconut (copra): It is prepared from ripe nuts and is available in
2 forms, viz. ball copra and cup copra. Ball copra is obtained from mature
unhusked nuts stored in the shade for 8-12 months. During this period the
coconut water is absorbed and kernel dries up. The husk and the shell are
then carefully removed. Cup copra is made from fresh or stored nuts by
cutting the kernel into halves and drying them under the sun or special
driers or kilns. Copra dried to 5% moisture content does not deteriorate if
not stored too long. If the moisture content exceeds 6% copra is liable to
mould and insect attack.
Dessicated coconut: It is prepared from the white fleshy layer of the kernel
commonly known as ‘meat’. The white meat is shredded or disintegrated

154
 NUTS AND OILSEEDS

and dried in a hot air drier to below 2% moisture. Dessicated coconut is

used in the manufacture of cakes, pastries and chocolates. It is an impor¬
tant ingredient of a variety of Indian sweets.

Groundnut
The groundnut peanut or monkey nut (Arachis hypogaea) is closely re¬
lated to the pea or bean. Amongst the biggest producers of groundnut are
China, India, the United States and Nigeria. Since the crop is tropical or
subtropical, other countries producing it are the Central African countries
and Argentina. Some plants grow erect to about 0.75 m high and some
remain prostrate.
The flower is typically leguminous. After fertilization the flower stalk
elongates, forcing the pods underground where they develop (Fig. 29). In the
erect varieties the pods remain close to the stem and are less scattered than
in the prostrate varieties. Hence the former are easier to harvest. Harvesting
is normally done by machines in the United States, but in other parts of the
world the crop is dug up with a spade.

Fig. 29. Groundnut pod

As regards composition, moisture is approximately 5% and, as with the

soybean, oil and protein content are high, about 50% and 25% respectively
(Table 22). Protein digestibility is 87%; BV 55%; PER 1.65; and NPU 43%
(Swaminathan, 1986). There are 2% crude fibre, 2% ash and a little starch,
usually less than 5%. Groundnut is also a good source of riboflavin thia¬
mine and nicotinic acid, although the thiamine is usually destroyed during
heat treatment.

155
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Table 22. Composition of groundnut and its products (per 100 g)

Part Water Energy Protein Fat Total Crude Ash

(g) (KJ) (g) (g) carbohydrates fibre (g)
(g) (g)

Seeds raw 6 2,360 25 48 15 2 2

Seeds roasted and 3 2,445 25 48 15 2 4

salted

Peanut butter 1 2,425 25 50 15 2 4

Defatted groundnut flour 8 1,550 50 10 3o 3 4

Groundnut is the third largest source of vegetable oil after soybean and
sunflower oil. There is also a good market for roasted groundnut and pea¬
nut butter. The oil is similar to soy oil. It contains 80% unsaturated fatty
acids (40% oleic, 35% linoleic) but the exact composition varies with type.
The typical flavour and odour is due to 1.8 g/tonne higher hydrocarbons
(C15, C19) and these, on separation, usually go with the oil rather than the
meal. On heating the flavour is accentuated (Swaminathan, 1987).
In the manufacture of peanut butter, the beans are roasted, cooled,
blanched and ground. The material is then salted using salt and sugar,
finely ground to avoid grittiness. Salted groundnut is submitted to steam
blanching and brushed to remove the skin. There are several types of blanch¬
ing, viz. wet, dry hydrogen peroxide and alkaline blanching. The object is to
bleach and remove the skin. The salt is usually added by dispersing it in
alcohol—soluble zein (maize protein)—to make it adhere to be groundnut.
An important use of groundnut is in cooking, particularly in West Africa.
Here maize and groundnut are either roasted together and eaten as such, or
the groundnut may be used in soups or stews. They are broken up first and
boiled in the soup, together with meat, fish and vegetables. Groundnut stews
are also popular in East Africa where they are consumed after first roasting
and then pounding into a paste. This may be either a coarse or a fine paste,
similar to the peanut butter eaten in the West.

Production and availability

India is the third largest producer of oilseeds in the world. Groundnut
being the major oilseed crop, covers 20 million ha, equalling 11% of the total
arable land in the country. The oilseed production is 5,610 thousand tonnes
for 1999-2000. There was a decline of the order of 19% due to continued
drought and indifferent monsoons. Nevertheless, oilseeds are second only
to cereals in agricultural production.
In the global context of oilseed production, India occupies an important
position. India is the largest producer of groundnut, castor, niger and sesame
seeds in the world. Its estimated production of other oilseeds (such as rape/
mustard, linseed, safflower and soybean) is considerable. India’s estimated

156
 NUTS AND OILSEEDS

production of coconut oil and edible rice bran oil are quite important, being
75,000 and 125,000 tonnes respectively.
Despite such impressive achievements in the farm output of oilseeds
during the past 25 years, today India is the world’s largest vegetable oil
importer.
Preparation of edible cake and oil: The steps involved in the preparation of
edible cake and oil from nuts and oilseeds are as follows:
1. Cleaning and dehusking
2. Removing oil from the kernel (free of husk) by one of the following
methods:
(a) Mechanical pressing (hydraulic pressing)
(b) Screw pressing
(c) Prepress solvent extraction, and,
(d) Direct solvent extraction.
Mechanical pressing: The material is cooked in steam at 65.6-93.3°C, the
period of cooking varying from 15-30 min depending on the material. The
moisture content of the cooked material will be about 15%. The cooked
material is formed into a cake by a special mechanical device in a press
cloth. The hydraulic press consists of 12-16 boxes each box receiving 1 cake
of the oilseed to be crushed. The maximum pressure applied is 2000 psi for
20-50 min. The oil content of press cake may vary from 5-8%, depending on
the material.
Screw pressing or expeller pressing: The operations in the screw press are:
steaming of the material as it passes through the conveyer to the press and
screw pressing of the material. The heat liberated in the material during
screw pressing will be high and may range from 104.4-132.2°C, depending
on the capacity of the expeller. The heat produced in medium size expellers
(about 104.4°C) does not affect the quality of the proteins but the heat pro¬
duced in large size expellers is high (132.2°C) and affects appreciably the
quality of proteins. In the medium size screw presses, the material is usu¬
ally pressed twice, the oil content of the meal obtained after first pressing
will be about 15-16% and that of the same meal after second pressing will
be about 5-8%.
Prepress-solvent extraction: Prepress solvent extraction method is used for
oilseeds containing more than 35% oil. Extraction of oil from oilseeds and
nuts by prepress solvent extraction method using food grade solvents is
pracitsed widely in the USA and other advanced countries for oilseeds such
as peanut, cotton seed and sesame. The process consists of the following
steps: (z) Cooking the oilseed in steam and expressing oil in a screw press by
single pressing, (ii) solvent extraction of the meal (containing about 20-25%
oil) using food grade hexane, and (zz'z) desolventizing the material. The
desolventizing process is carried out at temperatures of 93.3-104.3°C. The
protein quality in the meal obtained by the above procedure is not adversely
affected.

157
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Direct solvent extraction: This process is used mainly for oilseeds having
low fat content, e.g. soybean. The process consists of: (z) cooking of the
material in steam and flaking, (zz) solvent extraction of the flakes using food
grade hexane, (in) desolventising the meal.

Soybean
Soybean is a legume crop originally grown in India on the foot-hills of
the Himalayas and some other parts. However, exploition of its commercial
potential and the introduction of yellow soybean started with adaptive re¬
search in the mid-sixties. From less than 10,000 tonnes in 1969-70, soybean
production during 1993-94 has reached 390 million tonnes and it is ex¬
pected that during 1995-96, it would be over 4 million tonnes (Bhatnagar,
1994). Soybeans are the biggest source of vegetable oil. The oil is obtained
either by grinding the seed and extracting it with hexane or in some in¬
stances it is extracted by pressing.
Soy products: Traditional and non-traditional soy products in India is
given in Table 23 (Ali Nawab, 1993).
Table 23. Traditional and non-traditional soy products in India

Traditional product Non-traditional products

Cooking it Texturized soy protein

Hydrogenerated fat Health foods
Flours, flakes and grits Lecithin
Roasted/fried nuts Protein concentrate
Sprouted bean Protein isolate
Milk Protein hydrolysate
Paneer (todu) Liquid protein
Bakery products Yoghurt
Splits (dhal) Tempe
Vadi Sauce

Soy protein concentrate: To produce the protein concentrate the defatted

meal is often first treated with heat to make the proteins insoluble. It is
further extracted with alcohol, dilute acid or hot water. This removes sugars
and other low molecular weight compounds. In this way the protein content
is raised to as much as 70%.
Protein isolates: Processes have been standardized for the preparation
of protein isolates containing about 85-90% proteins from soybean. The
process for production of protein isolate from soybean or peanut consists of
the following steps (Fig. 30).
1. Solvent extraction of edible soybean,
2. Extraction of proteins with dilute sodium hydroxide at pH 8,

158
 NUTS AND OILSEEDS

Fig. 30. Preparation of soy protein isolate from defatted meal (Source: Muller and Tobin, 1980)

3. Precipitation of proteins at pH 4.5 from the extract by the addition

of hydrochloric acid,
4. Filtration of proteins and washing with water, and,
5. Solubilizing the wet protein in water by adjustment of pH to 7.0 and
spray drying.
Solvent extracted soybean or peanut meal: Soybean dhal or decuticled
peanut is expressed in a screw press to remove oil. The cake is extracted
with food-grade hexane, desolventized and powdered to pass through 50
mesh sieve.
Extraction ofproteins: The soybean is suspended in 15 parts by weight
of water. Concentrated sodium hydroxide solution is added with stirring till
the pH is increased to about 8.0. The extract is separated using a basket
centrifuge.
Precipitation ofproteins: The proteins in the extract are precipitated by
adjusting pH of the extract to 4.5 by the addition of hydrochloric acid. The
proteins are separated using a basket centrifuge and washed with water.
Solubilization of proteins and drying: The wet proteins are suspended

159
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

in 4 times the weight of water. The pH is adjusted to 7.0 by addition of

sodium hydroxide. The resulting sodium proteinate is spray dried.
Protein isolate from soybean or peanut cake can be used in the produc¬
tion of vegetable toned milk, infant foods, protein enriched biscuits and
bread.

Milk substitutes and infant foods

Milk prepared from soybean has long been used in China and other
Asian countries for feeding of infants. Improvements have been made re¬
cently in the processes by several workers. Methods for the preparation of
fluid milk from soybean follows. PAG has published specifications for milk
substitutes (Swaminathan, 1987).
Soybean milk: The boiling water technique for the preparation of soybean
milk yields a product without any beany odour. The method consists of the
following steps: (i) cleaning and dehulling of soybean in a mill; (ii) soaking
dehulled split bean in water for 5-10 hr; (izz) steaming the soaked bean for
30 min to destroy lipoxidase, trypsin and growth inhibitors; (iv) grinding the
cooked beans in boiling water; (v) filtration, addition of sugar, minerals and
vitamins; and (nt) homogenizing, steaming and bottling.
Soybean milk can be dried in a spray drier. The resulting powder can be
packed in the same way as milk powder in tins and used for feeding infants.
Peanut milk: Preparation of peanut milk is as follows:

Cleaning and light roasting of peanut kernel

I
Decuticling and removal of germs and spoilt seeds
l
Grinding, addition of calcium hydroxide and buffer salts
I
Filtration and fortification with vitamins and minerals and
I
Homogenization, steaming and boiling

Cleaning and light roasting: Good-quality peanut kernels are cleaned of

impurities and roasted lighjtly to facilitate removal of red skin.
Decuticling and removal of spoilt seeds: The cuticle (red skin) is removed
in a blanching machine. The germ is separated by sieving and the spoilt
seeds by hand picking.
Grinding and addition of water and buffer salts: The cleaned kernels are
ground to a smooth paste. The paste is mixed with 7 times the weight of
water in a blender. Calcium hydroxide solution is added till the pH of the
milk is adjusted to 6.8. A mixture of disodium phosphate and acid potas¬
sium phosphate having pH 7.0 is added to stabilize the milk.
Filtration and fortification: The milk is filtered through a fine cloth and
fortified with vitamins A, D, riboflavin, folic acid, vitamin B12 and minerals
(calcium and iron salts). Cane sugar is added at 7% level.

160
 NUTS AND OILSEEDS

Homogenisation, steaming and bottling: The milk is homogenized,

steamed, bottled and kept in a refrigerator till distributed.
The milk obtained from soybean or peanut can be used as a supplement
to the diets of pre-school and school children.

Textured vegetable protein and meat extenders

Soy protein isolate has been used as a meat substitute and to prepare
this, the soybean meal is suspended in dilute sodium hydroxide and centri¬
fuged. The meat extender may now be prepared in several ways. The 2 main
manufacturing processes consist of either obtaining an alkaline dispersion
of the protein, which is then mixed with colour and flavour and steam ex¬
truded, or the dispersion is mixed with gum, colour and flavour and ex¬
truded through fine dyes of 0.18 mm diameter. The extruded material is
stretched and layered on reciprocating tables, coagulated with live steam
and thus given a fibrous, more meat-like structure, in contrast to the rather
amorphous material obtained with the first method. These meat substitutes
are used extensively by mixing them with commercial meat products in the
manufacture of sausages and hamburgers.
Fabricated products made with spun protein analogues, even at 50%
level, are very similar to their all meat counterparts and have high accept-

Soy flakes

Extraction _Soy fibre concentrate

curd collection soy sugars

Soy protein isolate

Spinning
Neutralizing

Spun soy protein isolate fibrils (tow)

-> Flavouring colouring

Optional

Binding cooking

Cutting
Freezing

Spun protein analogues

Fig. 31. Schematic flow diagram for the production of spun protein analogues (Source: Quass and Dewson,
1979)

161
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

ability. The flavour and texture problems associated with many other meat
extenders which restrict their use to 10-30% can be overcome by use of
spun protein analogues. These spun protein analogues are very adaptable
to applications with sectioned and formed products and in some cases actu¬
ally improve product quality (Fig. 31).

Extruded products (role of extrusion process)

Extrusion cooking, a process of high temperature, high pressure short-
time cooking under controlled conditions of moisture, is particularly suited
for high-protein low-fat materials like solvent extracted soy flour or ground¬
nut flour.
Extrusion technology: The process is based on the principle of short-time-
high-temperature processing. The material to be processed is passed through
a barrel with a screw-conveyor. The screw is specially designed such the
matter being conveyed is subjected to increasing resistance and pressure as
it moves along. High temperature is thus generated and the material is
cooked. However, the time during which the material is subjected to high
temperature is very short, and hence the nutritional quality of the product
is not impaired in the process.
Extrusion cooking is a versatile process. Low cost food extruders are
being used for preparation of weaning foods in some countries for mass
feeding programme by the respective governments (Mallesh, 1995). Sche¬
matic diagram of an extrusion cooker is given in Fig. 32).

Fig. 32.Extrusion coooker. A, Feed; B, steam injection; C, water injection; D, steam, injection;
E, plate with outlet hole; F, steam jacket (Source: Filno et a/., 1974)

162
 NUTS AND OILSEEDS

The moisture in the material is usually adjusted to about 20-40% be¬

fore it is fed into the cooker. After being subjected to the heat-cooking, the
material emerges out through the die which is placed at the end of the
barrel. This causes a sudden release in pressure and hence it expands. As
the material comes out of the barrel, it meets a revolving knife, mounted in
front of the barrel. This cuts the material emerging from the die-head and
shapes it. The material then passes on into hot-air driers which reduce the
moisture to 6-7%. It is then graded on sieves and packed.
Advantages of extrusion cooking: Following are the advantages of the extru¬
sion cooking:
1. Extrusion cooking is high-temperature-short-time cooking and hence
has the advantage of minimum damage to the nutritional quality. At the
same time anti-nutritional qualities are removed and the product is sterile.
2. Extruded or dried food is crunchy and acceptable. With high protein
formulae, it is possible to get the meat-like texture, while with high carbo¬
hydrate mixtures, crunchy expanded, bread-like snack foods can be ob¬
tained. The texture could be altered, by modifying the configuration of the
section.
3. Extrusion cooking has been used for the production of snack foods,
pet-foods, foods for social welfare feeding programmes and for textured pro¬
tein foods.

Quality consideration
The BIS has set up standards for defatted soy meal. The acceptance
standards set by the Mysore snack foods for soy flour are given in Table 24.

Table 24. Specifications for extruded materials (Mysore snack food)

Soy flour Specifications

Moisture 7.5-8.5%
Protein 52-54%
NSI 45-55%
Fat Less than 1 %
Ash 6-6.5%
Acid insoluble ash 0.1-0.2%
Fibre 2-3.5%
Colour Yellow to light brown
Appearance Uniform no black specks hulls and foreign matter
Size Spherical or cylindrical, 15-25 mm
Colour Pale yellow to grey
Moisture 3.5-5.0%
Water absorption 250-280 g/100 g
Bulk density 240-280 g/litre
Powder Less than 0.2-0.5%
NSI (nitrogen-soluble index) % water soluble nitrogen of total nitrogen

Source: Rangaswamy Chinnaswamy (1989)

163
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Of late, technology has revolutionized the snack food industries in the

western hemisphere. Today, over $ 20 billion worth of snack foods are pro¬
duced using this technology and consumed in the continent United States
alone. This consumption rate increases by 3% every year in the United States.
There are 2 types of extruders in the market—single and twin screw
extruders. The single screw extruder contains a smooth, deep-flighted
Archemides screw within a grooved barrel. The twin screw extruders con¬
tain 2 co-rotating or counter rotating screws inside the barrel.

The main difference between single and twin screw extruders is the
number of screws inside the barrel. These extruders have heating/cooling,
and other provisions on the barrel to add water and/or ingredients, depend¬
ing on the type of processing and the product. They consume less of energy
and show higher rate of production than single screw extruders. Hence, the
industries prefer them over single screw extruders. Further, these extruders
are specifically designed for a speciality product (Rangaswamy Chinaswamy,
1989).
Extrusion equipment can be generally classified as: low-shear cooking
extruders, collect extruders, high-pressure forming extruders, high-shear
cooking extruders, and pasta extruders. Many soft-moist foods, pet foods or
high moisture foods are produced with low-shear cooking extruders. Pasta
extruders produce low shear, and little or no cooking during extrusion.
Pregelatinized products are pressurized in high-pressure forming extruders
to pass through a specific die for shaping, sizing or to form a pellet for
further processing. In collect extruders, shear and mechanical dissipation
of energy gelatinize the starch without external heating, but in high-shear
extruders, uniform external heating is applied for the purpose
(Chandrasekhara, 1989).
During the extrusion cooking process, the material is conveyed by the
screw from the feed hopper to the die-section; the particles, cells and gran¬
ules are ruptured, plasticized and restructured due to shear, heat and pres¬
sure. Gelatinization of starch, denaturation of proteins and degradation and
reorientation of molecules take place during the process. In some cases,
complex formation is noted between lipid, amylose, protein, sugars and amino
acids. The plasticized matter is puffed, texturized, cooked or a combination
thereof when it leaves the die nozzle. These changes, however, can be con¬
trolled with processing conditions and chemical additives. Though molecu¬
lar changes occur during extrusion-cooking, the basic raw material quality
is still reflected in the product quality. Although extrusion cooking is highly
exploited, the basic understanding of chemical changes that take place dur¬
ing the process is still limited.
In western countries, the advantages reflected by savings in energy,
labour and space, besides high production rate has enabled extrusion tech¬
nology to almost replace batch type processes to produce snack foods. A
number of products are also produced in developing countries by extrusion-

164
 NUTS AND OILSEEDS

cooking using cereals, legumes and seaweed polysaccharides. In general,

there are 4 categories: (z) flour-based products (breakfast cereals, snacks
and food thickeners); (zz) protein-based products (textured vegetable pro¬
teins and protein enriched cereals), (izz) pet foods (dog and fruit gum); and
(iv) reactants (caseinate, modified starches and flours).
Another class of extruded products called fabricated foods has also ap¬
peared on the shelves of supermarkets. They are speciality products and
are rich in certain chemical constituents to meet a specific nutritional re¬
quirement. They can be high fibre cereals, high protein cereals or low fat,
low calorie breakfast cereals. Such foods are prepared from a mixture of
cereals, bran and proteins. Further, several commercial products consist¬
ing of outer layers made by cooking extrusion and filled with pumpable
centres have been introduced to the market recently. Extruders are also
used to prepare suitable dough to obtain flat breads and crumbs. In this
situation, extruders help rupture the gas cells formed during dough fer¬
mentation and thus reduce the loaf volume. Other areas where extruders
have found application are dextrin and pregelatinized starch manufactur¬
ing and co-extrusion of animal and plant proteins—a new class of food.
Since the IQGO’s, extrusion technology has gained momentum in growth.
By understanding the chemical and molecular changes and operation of
extrusion variables on these changes, applications such as (z) parboiled rice
from broken rice, and corn starches, (zz) bioplastics from starches, (z'z'z) fla¬
vour encapsulation, and pharmaceutical capsules, (iv) biotechnology appli¬
cations (fermentation and glucose syrup production), (y) degermination of
spices, (vi) oil extraction, (vu) rice bran stabilization, (znil) destruction of
aflatoxins and gossypol in peanut and cotton seed kernels, (zx) arresting
retrogradation in processed foods, (x) sterilization of blood meal, (xz) sterile
process for cheese, (xzz) pressurized chemical reactor, and (xz'z'z) tool to meas¬
ure dough viscosity have been envisaged.

REFERENCES

Ali, Nawab. 1993. Soybean the complete food. Food Technology 1(1).
Bhatnagar, P.S. 1994. ‘Recent technological advances in research and development of soyabean
in India’. Paper presented in the Regional Experts Consultation on Asian Soyabean Net¬
work, held during 21-25 February 1994 at Chiongmai, Thailand.
Chandrasekhara, M. 1989. Role of extrusion cooking in food processing, (in) Trends in Food
Science and Technology, pp. 49-53. Association of Food Scientists and Technologists
(India), Mysore.
FAO. 2000. Bulletin of Statistics. Food and Agriculture Organization of the United Nations,
Rome.
Muller, H.G. and Tobin, G. 1980. Nutrition and Food Processing, pp. 245-47. AVI Publishing
Co., Inc., Connecticut.
Quass, W. and Dawson, H.N. 1979. Use of spun soy protein in meat systems. Journal of
American Oil Chemists’ Society 56(3): 341-42.

165
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Rangaswamy Chinnaswamy. 1989. Role of extrusion process, (in) Trends in Food Science and
Technology, Association of Food Scientists and Technologists (India), Mysore: 57-58.
Swaminathan, M. 1986. Principles of Nutrition and Dietetics. The Bangalore Printing and Pub¬
lishing Co., Ltd., Bangalore.
Swaminathan, M. 1987. FoodScience, Chemistry and Experimental Foods, pp. 161-67. Bangalore
Printing and Publishing Co. Ltd., Bangalore.

LEARNER’S EXERCISE

1. List the important nuts and oilseeds in India.

2. Discuss any two of the important nuts and oilseeds in detail with reference to the com¬
position and processed products.

166
 Fats and
oils

O and fats have been used by man in food preparations for many
ils
centuries now. In the past, butter or ghee was used because it added
richness of flavour and colour to the food preparation. Today, in addition to
butter, many oils and fats of animal and vegetable origin and many prod¬
ucts developed from them are consumed by man. Many foods contain large
amounts of fats that are not apparent in their appearance, e.g. avocados
contain 16%, egg yolk 31%, chocolate 35%, beef (some cuts) 41%, almond
58% and cheese 32% fat. World production of oils vis-a-vis Asia and India is
given in Table 25 (FAO, 2000).

Table 25. Production of oils (’000 tonnes) during 2000

World Asia India

Oil from groundnut 4,526,510 3,383,035 1,940,000

Oil of soybean 18,837,712 2,878,239 300,000
Oil of rice bran 733,427 719,477 400,000
Oil of coconut 3,258,018 2,822,942 280,000
Palm oil 15,613,361 12,681,000 —

Oil of palm kernel 1,968,906 1,421,058 —

Oil of sunflower seed 8,314,840 1,384,945 500,000

Oil of cotton seed 3,636,549 1,708,839 458,000

NUTRITIONAL IMPORTANCE

Oils and fats are important sources of our energy requirements. Weight for
weight, they furnish 2.25 times more energy than proteins and carbohy¬
drates. Thus, they help reduce the bulk of food we take. Besides being im¬
portant source of energy, oils and fats are excellent sources of fat, soluble
vitamins A, D, E and K and play a part in biosynthesis of several long-chain
alcohols.
Oils provide the essential fatty acid, linoleic acid, which is needed for
human health. Intake of saturated fatty acids in excess amounts increases
the level of serum lipids and the incidence of arteriosclerosis and heart
disease. A high level of consumption of unsaturated acids is thus necessary
for normal health. Fatty acid composition of oils commonly used in India is
given in Table 26.

167
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Table 26. Fatty acid composition of commonly used oils

Oil Saturated Mono- Poly-

unsaturated unsaturated

Coconut (Cocus nucifera) 91 8 1

Cotton seed (Gossypium sp.) 34 26 40
Groundnut 20 54 26
(Arachis hypogaea)
Indian mustard 6 73 21
(Brassica juncea)
Niger 12 35 55 .
(Guizotia aPyssimca)
Palm 80 13 7
(Elaeis guineensis)
Safflower 11 13 76
(Carthamus tinctorius)
Sesame 14 46 40
(Sesamum indicum)
Soybean 15 25 60
(Glycine max)
Sunflower 8 34 58
(Helianthus annuus)

Source: CSIR, 1952, 1956; CFTRI, 1976

Essential fatty acids from fats are the components of membranes of

living cells. They are also used by the body to make prostaglandins involved
in a large variety of vital physiological functions. These acids play a role in
immunity. Decreased availability of essentail fatty acids can also lead to
impaired growth and diminished mental and physical capacities.
Various types of fatty acids in the diet have different effects on health.
Saturated fatty acids and cholesterol present in the diet, tend to increase
serum total and LDL-Low density lipoprotein cholesterol and consequently
the risk of cardiovascular disease. When n-6 polyunsaturated fatty acids
are substituted for saturated fatty acids, they lower serum LDL-cholesterol;
n-3 PUFAs also lower serum cholesterol, but they are more effective in low¬
ering serum triglyceride levels (Ramakrishnan and Venkat Rao, 1995). The
main dietary sources of these cholesterol raising saturated fatty acids are
dairy and meat products and some vegetable oils, such as coconut, palm
and palm-kernel oils. Dietary cholesterol is found mainly in egg yolks, certain
shell fish, organ meats and to a lesser extent, in other meats and dairy
products. The intake of these foods must be curtailed, since they counteract
the effects of saturated fatty acids. Increased consumption of vegetable oils
is widely advocated.
Fats are slow in leaving the stomach and hence retard digestion. This
delays the pangs of hunger. There is, however, no difference in the digestibility
of different fats that are ordinarily constituents of foods. They are utilized
up to 95-98%. The difference in digestibility that does exist is related to the

168
 FATS AND OILS

melting point of the fat. Those which melt below 43°C are completely di¬
gested, whereas those melting above 43°C are more slowly digested and less
completely absorbed.
Oilseeds are also rich in proteins and oilseed cake obtained after ex¬
traction of oils from seeds can be processed to produce protein-rich foods.
Such foods are in market and have helped solve protein deficiency of vul¬
nerable sections of our population, such as infants, children and pregnant
mothers.
In spite of these well-known merits of oils and fats, the consumption of
dietary fat in India is very low. Our per caput intake is of the order of 4-5
kg/annum compared with 40-50 kg consumed in advanced countries. Much
of our malnutrition, particularly amongst children, is due to low intake of
fats. The FAO/WHO expert group has recommended that 30-35% of our
total calorie requirements must be met by oils and fats and ratio of satu¬
rated to polyunsaturated fatty acids should be 1:1. The minimum nutri¬
tional requirements of fat specified by the Indian Council of Medical Research
is 20 kg/caput/annum. The average dietary consumptions of oils and fats
in India is thus about one-fourth to one-fifth of the nutritional require¬
ments. Immediate steps are to be taken to increase the availability of oils
and fats and its consumption in India to meet the energy needs of our popu¬
lation (Shakunthala and Shadaksharaswamy, 1987).

FUNCTIONS OF OILS AND FATS IN FOODS

Besides their nutritional function, oils and fats have other uses which de¬
rive principally from their distinct physical properties. They contribute to
the tenderness, flavour, colour and texture of food products. They also serve
as chief ingredients in preparing foods that form emulsions and as cooking
media.

Tenderness
One of the most important functions is to tenderize baked products. In
absence of oils and fats, the gluten strands will be held firmly together as
solid mass. Fats being insoluble in water, interfere with gluten development
during mixing. Thus fats act as shortenings in the preparation of baked
products.
Butter, margarine, a blend of vegetable and animal fats, and hydrogen¬
ated fats and oils are used as shortening agents. Super glycerinated
shortenings are used for baking.
In biscuits, a hard fat must be used so that the fat can be distributed in
small pieces to give the desired flakiness to the biscuits. Muffins require
that the fat be fluid during mixing. Shortened cakes are made using a plas¬
tic fat which combines readily with the ingredients in flour mixture. Chiffon
cakes are formulated with the use of oil. Butter and commercial shortenings

169
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

are used in the preparation of cookies. Thus, the type of fat used as short¬
ening in making pastries depends on the type of product desired. Butter is
usually used in puff pastry.
Fats also contribute to the incorporation and retention of air in the form
of small bubbles in the batter. Carbondioxide and steam diffuse into these
air cells during baking. Thus, fats contribute to the grain and volume of the
baked products.

Flavour
Some fats influence the flavour of the food. Fats that are used for sea¬
sonings, table use and salad dressings, possess distinctively pleasing fla¬
vours. Butter, margarine and olive oil are commonly used for salad dressings.
Cotton seed oil, corn oil, groundnut oil and soybean oil lack flavour and are
used for salad dressing when a bland flavour is required.

Texture
Fats have textural effects in foods. They affect the smoothness of crys¬
talline candies and frozen desserts through the retardation of crystallization
and the gelatinization of starch in starch thickened mixtures. They contribute
to the juiciness of meats and the foam structure of whipped cream.

Emulsion
Fats constitute one of the essential constituents in food emulsions. In
most food emulsions, oil is dispersed or discontinuous phase and water is
the dispersion medium or continuous phase. For stabilization of emulsion,
an emulsifying agent is required. Various substances commonly used as
emulsifiers are egg yolk, whole egg, gelatin, starch paste, vegetable gum,
casein and fine powders, such as those of paprika and mustard.
Salad dressings, such as mayonnaise, french dressings, and cooked
salad dressing are permanent or semipermanent emulsions of oil-in-water.

PROCESSING OF OILS AND FATS

Oils and fats do not occur free in nature. They occur in animal tissues, and
in seeds and fruits from which they are isolated, refined and processed for
specific use. Fats are extracted from animal tissues chiefly by rendering
and from other sources by pressing and solvent extraction.

Rendering
In this process, fat from animal tissues is extracted by heat. Chopped or
minced tissues are heated with water (wet rendering) or in its absence (dry
rendering). In the former method, it is more common to use steam which
results in good disintegration of cells and efficient separation of fat. In dry
rendering the tissue is heated with steam in vacuum containers. An improved

170
 FATS AND OILS

technology involves the division of the fatty tissues into fine particle size
after which flash heating is applied for 15 sec. The product is then pulver¬
ized and centrifuged. This method gives a high yield, and a bland and stable
product.

Pressing
In India, oil has been obtained by processing oilseeds in village ghanis
(made of pestle and mortar), driven by bullocks, from time immemorial.
Power ghanis are now replacing non-power units.
The modern method of oil extraction by pressing is by the use of high-
pressure expellers. In this process, the oil-bearing material is cleaned, tem¬
pered and dehulled, crushed or flaked and then passed through expeller,
when the oil separates out. Deoiled cake is a good cattle feed. About an 80%
of the oil is produced by this method.

Solvent extraction
Extraction of oil from expellers is not a very efficient method, as result¬
ing cakes contain appreciable amounts of oil. Therefore, it is now common
to extract oils by solvent extraction or by a combination of pressure and
solvent extraction. With materials containing a low percentage of oil, solvent
extraction is the only practical method of removing oil. Various organic sol¬
vents could be used, but the most commonly employed solvent is hexane.
After extraction of oil, the solvent is removed from the oil. The residue after
solvent extraction can be processed as edible flour. About one tenth of the
oil produced in the country is obtained from solvent extraction.

Refining
Oils extracted by the above methods are crude and contain many other
constituents like free fatty acids, unsaponifiable matter, gums, waxes, mu¬
cilaginous matter, variety of colouring matter, metallic contaminants, un¬
desirable odouriferous constituents etc. In refining, the suspended particles
are removed by filtration or centrifugation. The free fatty acids are removed
by alkali treatment. When the free fatty acid content is high as in palm oil
(5%) it is removed by blowing steam through hot oil under vacuum. This
results in both deacidification and deodourization. Any remaining free fatty
acids are removed by neutralization. Pigments are removed by bleaching
using adsorbents like activated earth or carbon or, in special cases, chemi¬
cal bleaching agents. Finally, the oil is deodourized by injecting steam through
the heated fat kept under reduced pressure. Techniques for continuous
bleaching and deodourizing are available.

SOYBEAN

The processing of soybean involves the following steps:

Cleaning and decuticling: Soybean is cleaned of all impurities. The cleaned

171
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

seed is passed through a huller to remove the hulls. The dehulled seed is
split.
Steaming and drying: The dehulled seed is soaked in water for 1 hr and
water is drained off. The wet material is heated in steam at 6.34 kg pressure
for 30 minutes to inactivate trypsin and growth inhibitors, haemagglutinins,
etc. The steamed seed is dried under the sun or in a tunnel drier.
Screw pressing or solvent extraction: The oil from heat processed seed is
removed by pressing in a screw press or by solvent extraction.
Powdering: The cake is powdered in a hammer mill to pass through 50
mesh sieve.

GROUNDNUT MEAL

The processing of groundnut for edible meal consists of the following steps:
Cleaning: Good quality groundnut kernels are cleaned of all impurities.
Roasting and decuticling: The kernel is roasted lightly for 5 to 10 min. The
red cuticle is removed by rubbing. The germs are separated and fungus-
affected kernels are removed by hand picking.
Screw pressing: The cleaned decuticled kernels are pressed in a screw
press (expeller) for removing the oil. The resulting white cake containing
about an 8% oil is powdered in a hammer mill. The cake can be extracted
with food grade hexane to obtain fat-free flour.

SESAME

The processing of sesame consists of following steps:

Cleaning and dehulling: Sesame seeds are cleaned of impurities. The
dehulling is carried out by soaking the seed in water or in dilute alkali and
removing the skin by rubbing. The dehulled seeds are dried in a tunnel
drier.
Screw pressing or solvent extraction: The dehulled seeds are pressed in a
screw press. The resulting white sesame cake containing about 10% oil is
powdered in a hammer mill.

COCONUT

The processing of coconut consists of the following steps:

Preparation of copra: Coconut meat is cut into small pieces and dried in a
tunnel drier.
Screw pressing or solvent extraction: The dehulled seeds are pressed in a
screw press. Food grade hexane is used to completely remove the oil.

COTTON SEED

The processing of cotton seed consists of the steps are given here.

172
 FATS AND OILS

Cleaning, delinting and dehulling: Good quality cotton seed is cleaned of

impurities. It is delinted and dehulled.
Steaming of the kernels: The kernels are steamed for 15 min. to fix free
gossypol in the bound form.
Screw pressing or solvent extraction: The steamed kernel is pressed in a
screw press. The resulting cake contains 8-10% oil. If a fat-free flour is
required, the cake can be extracted with food grade hexane.

SUNFLOWER SEED

The processing of sunflower seeds for oil and edible meal involves the fol¬
lowing steps.
Cleaning and decortication: Good quality sunflower seeds are cleaned of all
impurities. The cleaned seeds are decorticated in a special type of decorticator.
Screw pressing and solvent extraction: The kernel is pressed in a screw press
to separate the oil. The residual cake contains about 10-15% oil. It can be
extracted using food grade hexane.

EXTRACTION OF OILS FROM ANIMAL FATS

Oils and fats are essential ingredients of foods. Several animal and vegeta¬
ble fats are used in food preparations. Their use depends on the properties
of the fat, their availability and the culture of the area for their use. The
animal fats used are butter and lard.

Lard
Lard is an animal fat from hogs. It is very popular in western countries
as a low cost, flavourful substitute for butter in frying and baking. It is
obtained by heat rendering of fatty tissues. The quality of lard depends on
the part of the body of the animal from which the fat is obtained and the
feed given to the animal. Lack of uniformity in some of the physical proper¬
ties of lard, such as flavour and granular structure, and susceptibility to the
development of rancidity come in the way of its use. These are overcome by
modifying the fat in several ways, including bleaching, homogenization,
deodourization, addition of emulsifiers and addition of antioxidants.

Tallow
It is obtained from beef by the process of rendering. Rendering consists
of heating meat scraps for melting of fat. As the melted fat then rises, the
water and remaining tissue settle below. The melted fat is then separated
by skimming or centrifugation. Dry heat rendering which cooks the tissue
under vacuum to remove moisture, or wet rendering which utilizes water
and steam, or low temperature rendering which uses just enough heat to
melt fat can be adopted. Low temperature rendering can produce a fat of
higher colour, but where more meats flavour is desired higher-temperature

173
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

rendering is used. Rendering also is used to obtain oil from whale fish tis¬
sue. In its simplest form rendering can be carried out in a heated kettle; but
large capacity modern rendering plants are highly engineered and same
employ continuous rendering methods (Potter, 1968).

Fish liver oil

Fish oils are of 2 kinds, viz. liver oil and fish body oil. Liver oil is the
natural source of vitamin A and to a lesser extent vitamin D. Fish such as
cod, halibut and shark are good sources of fish liver oils. The oil and vitamin
A content vary with fish. Body oil is obtained from fish such as sardine,
herring and salmon.
Liver oil is obtained by various methods. One common method is cook¬
ing good quality minced fish liver at 85°-95°C. This results in disintegration
of liver cells and freeing of oil. The oil flooding on the stream condensate can
be skimmed off by centrifugation. About 300 kilo litres of shark liver oil per
annum are produced in the country (Shakunthala and Shadaksharaswamy,
1987).

Butter
Butter is the fat or cream that is separated more or less completely from
other milk constituents by agitation or churning. The mechanical rupture of
the protein film around the fat globules allows the globules to coalesce.
Butter formation is an example of the breaking of the oil-in-water emulsion
by agitation. The resulting emulsion that forms in butter itself is a water-in-
oil-emulsion, with about 18%, water being dispersed in about an 80% fat
and small amount of protein acting as emulsifier.
Butter is made from either sweet or sour cream. Butter from sour cream
has a more pronounced flavour. The cream may be allowed to sour natu¬
rally or it may be acidified by the addition of a pure culture of lactic acid
bacteria to pasteurized sweet cream. The latter method results in butter of
better flavour and keeping quality, as it excludes many undesirable types of
microorganisms that may cause off-flavour.
After churning separates the butter fat from other constituents, the
mass is washed, salted and worked to distribute the salt and to remove
excess water or butter milk. Some sweet-cream butter is marketed unsalted
as sweet butter but salted butter is preferred by most persons.

HYDROGENATION AND WINTERIZATION

Hydrogenation
Hydrogenation of oils has been one of the significant advances in the
technology of oils and fats. By this process, liquid fats can be converted into
semi-solid and solid fats for use as shortening in the preparation of biscuits,
cakes, butter substitutes etc. The hydrogenated fat has very good keeping

174
 FATS AND OILS

quality. Hydrogenated fats are prepared from refined deodourized oils. It is

carried out under pressure at 100°-120°C in the presence of catalysts pre¬
pared from nickel, platinum or palladium for period of 1-3 hr, till the fat is
hydrogenated to the desired level. During hydrogenation, the double bond
present in unsaturated fatty acids take up hydrogen and resulting in satu¬
rated fatty acids, as given below by Swaminathan (1990).
Oleic acid +2H —> Stearic acid
Linoleic acid +2H —> Oleic acid riso-oleic end
Linoleic acid +4H —> Stearic acid
Linolenic acid +2H —> Linoleic acid
Linolenic acid +4H —> Oleic acid
Linolenic acid +6H —> Stearic acid

Winterizing
Triglycerides in vegetable oils are mixtures of fatty acids with some long
chain saturated and more long-chain unsaturated acids. Some manufactuers
cool the oil and filter out the solidified particles before the oil is packaged for
sale. Oil that has been so treated may be labelled winterized, although such
labelling is not mandatory. Oil that has not been winterized may become
cloudy when stored in a refrigerator. If the oil stands at room temperature
for a while the solid particles will melt and the oil clarity is restored. An
example of this may be found in olive oil, which is about 75%
monounsaturated and which becomes cloudy and viscous when refriger¬
ated because the monosaturated fatty acid is liquid at room temperature
but solid at refrigeration temperature (Gladys etal, 1978).

HOMOGENIZATION AND EMULSIFICATION

Homogenization
In the homogenization fat globules are broken up mechanically to less
than 1 micron in diameter, so that fat does not rise to surface to form a
cream layer. In homogenized milk the process consists of forcing milk heated
to about 57° to 60°C through a very small orifice at high pressure. All ho¬
mogenized milk should be pasteurized after homogenization to destroy the
enzyme-lipase which otherwise would cause milk to become unfit for hu¬
man consumption within a few hours due to the development of bitterness
and rancidity. One disadvantage of homogenized milk is that milk fat can¬
not be separated as cream in a cream separator. The fat in homogenized
milk is more readily digested by infants than that from ordinary milk.
This process consists of pumping the milk under high pressure through
special valves which divide the normal fat globules into many smaller ones.
These small fat globules are not able to rise by gravity and therefore the
process provides a uniform or homogenous product.

175
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Emulsification
It is one of the properties of fats that influence the role of fat in cookery.
The specific gravity of oils and fats is about 0.9, which indicates that they
are lighter than water. Though insoluble in water, they can form an emul¬
sion with water when beaten up with it to form tiny globules in the presence
of suitable emulsifying agent. Butter is an emulsion, so also is cream. The
presence of minute amounts of milk protein helps stabilize these emul¬
sions. Lecithin, a phospholipid, from egg yolk, helps stabilize mayonnaise, a
salad dressing made from vegetable oil. Emulsification of fats is a necessary
step in a number of products such as cakes, ice cream and other desserts
(Sumati and Shalini, 1990).
The most important use of surface active agents is to form emulsions or
to facilitate the mixing of fats and oils in a solid wet mass like doughs. The
emulsifying power of surface active agents are usually empressed by the so-
called Hydrophilic-Lipophilic Balance (HLB) system.
It is a numerical expression indicating the emulsifying power of the
agent. Surface active agents with low HLB level to form water in oil (w/o)
emulsion, whereas these with high HLB tend to form oil in water (o/w)
emulsions (Swaminathan, 1987).

PREPARATION OF PEANUT BUTTER

The process of preparation of peanut butter consists of following steps:

Cleaning and roasting: Good quality peanut kernel is cleaned of all impu¬
rities. It is roasted to moderate degree till a pleasant aroma develops.
Blanching and removal of germ and spoilt seeds: The testa (red skin) is re¬
moved by passing the roasted kernel through a blanching machine. The
germs are separated by sieving and the spoilt kernels by hand-picking.
Grinding and packing: The kernels are ground in a grinding machine to a
medium grind. Hydrogenated fat containing vitamin A is added at 5%, as it
helps prevent separation of oil. Sodium chloride is added at 2% level. The
mixture is ground to a smooth paste and packed in bottles.
Peanut butter is consumed widely by children in the USA It can be
easily fortified with calcium salts and essential vitamins and used a supple¬
ment to the diets of pre-school and school children in developing countries.

REFERENCES

CFTRI. 1976. Proceedings of Symposium on Oils and Fats, held at Mysore, Central Food and
Technology Research Institute, Mysore.
CSIR. 1956. Wealth of India, Vol.IV, Council of Scientific and Industrial Research, New Delhi,
p. 272.
CSIR. 1952. Wealth of India, Vol.III, Council of Scientific and Industrial Research, New Delhi,
p. 136.
FAO, 2000. Bulletin of Statistics 2000. Food and Agriculture Organization of the United Na¬
tions, Rome.

176
 FATS AND OILS

Gladys E. Vail, Jean. A. Phillips, Lucile Osborn Rust, Ruth M. Griswold and Margeret M.
Juslin. 1978. Foods, edn 7. Houghton Mifflin Co., Boston.
Potter, N.N. 1968. Food Science, The AVI Publishing Co., Inc. West Port, Connecticut.
Ramakrishnan, S. and Venkat Rao, S. 1995. Nutritional Biochemistry. T.R.Publications.
Shakunthala, M.N. and Shadaksharaswamy, M. 1987. Foods : Facts and Principles. Wiley
Eastern Ltd, New Delhi.
Swaminathan, M. 1987. Food Science, Chemistry and Experimental Foods. Bangalore Printing
and Publishing Co. Ltd, Bangalore.
Swaminathan, M. 1990. Food Science, Chemistry and Experimental Foods. Bangalore Printing
and Publishing Co. Ltd, Bangalore.
Sumati R. Mudambi and Shalini, M. R. 1990. Food Science. Wiley Eastern Ltd, New Delhi.

LEARNER’S EXERCISE

1. What is hydrogenation? How does it affect the properties of an oil?

2. Explain briefly the types of rancidity that takes place in fats. Describe a method for
measuring the hydrolytic rancidity and oxidative rancidity in fats.
3. How would you evaluate the stability of a fat?
4. Describe the assessment of fatty acid composition of a lipid.
5. How do fats deteriorate? Discuss the measurement of fat deterioration.
6. Give an account of the nutrient importance of fats and oils in our diet. How do you take
care of used oils?
7. What happens when you use continuously reheated oil at higher temperature and their
effect on health.
8. What are the functions of fats and oils in food proportion? Mention the care to be taken
while using and storing fats and oils.
9. Explain function of fats and oils in cooking.
10. What changes occur in fats and oils during long storage? How can these be arrested?

177
 Fruits and
vegetables

FRUITS

F commonly designated as fruits in food preparation are fleshy or

oods
pulpy in character, often juicy and usually sweet with fragrant, aro¬
matic flavours. Fruits may be classified as simple, aggregate or multiple,
depending on the number of ovaries and flowers from which the fruit devel¬
ops. Simple fruits which develop from a single ovary in 1 flower, are citrus
fruits such as oranges, grape fruit, lemons, peaches which have stone or pit
enclosing the seed, pomes such as apples and pears which have core. Ag¬
gregate fruits developing from several ovaries in 1 flower are raspberries,
strawberries and black berries. Pineapple is an example of a multiple fruit
that has developed from a cluster of several flowers.

Another classification of fruits

I. Berries (except grapes) IV. Grapes

Brambles, Black berry, Logan berry and
Raspberry V. Tomato

Other berries VI. Other tropical and sub-tropical fruits

Avacado, banana, aonla, cashew fruit,
Blue berries, Cran berries, Goose berries and
passion fruit, dates, guava, figs, jambu fruit,
Strawberries
jack fruit, mango, papaya etc., pineapple,
pomegranate, sapota, seetapal, wood
II. Citrus fruits
apple, bael and litchi
Citron, Grape fruit, Lemon and Orange

III. Drupes
Apricot, Cherry, Peach and Plum

Composition
Fresh fruits have a high water content (70-96%), varying amount of
carbohydrate (3-27%) and fibre (0.2-3.1%) and a low content of protein, fat
and minerals. Fruits are important sources of provitamin A and vitamin C.
Some dry fruits are rich sources of minerals, calcium and iron. Fruits contain
pigments, which are responsible for their colour. The orange-yellow fruits
contain beta carotene, which is converted to vitamin A, when absorbed from
the digestive tract. Most fruits contain an edible part combined with some

178
 FRUITS AND VEGETABLES

inedible part. There are some fruits which are wholly edible such as berries,
guava, grapes and tomato, whereas apples, pears, peaches, cherries and
sapota have 85-90% edible portion. Other fruits such as bananas, sweet
lime, orange, and pineapple contain one-third or more inedible refuse. The
carbohydrate in the fruit is made up of fructose, glucose, sucrose and starch
as well as some fibre. The carbohydrate content of fruits varies from 3 in
watermelon to 27% in banana. Most of the energy of fruits (80-96%) is
provided by the sugars present. Therefore, fruits or fruit juices are given
when a quick source of energy is needed, e.g. as appetizers and as refresh¬
ing drink for athletes.
Fruits are generally acidic and sweet. There are a number of other flavour
components, which give distinctive flavour and taste to each variety of fruit.
Fruits have a protective tissue, which may take forms such as peel, skin
and rind. Surface of these protective structures is waxy, which helps in
retaining the moisture, which is necessary to retain the freshness of a fruit.

Nutritional contribution
Fruits are valued for their contribution as quick sources of available
energy. The soft texture of most fruits permits their use in infant diets, diets
for the aged, and the sick. The fruits with lower carbohydrate content find
place in energy restricted dietaries also (Sumati and Shalini Rao, 1993).
In India, there are fruits, such as aonla, guava, cashew fruit, which are
extremely good sources of vitamin C, providing 135-600 mg vitamin C per
100 g edible portion. The quantities of fruit eaten may have to be increased,
if a source containing medium or low amount of vitamin C is used. Fruits
such as papaya, orange and mango, which contain orange-yellow pigment
carotene, provide the precursor of vitamin A.
Fruits are not very good sources of calcium. Berries such as strawberry,
raspberry, mulberry, sapota, peaches etc. are fair source of iron. Dry fruits,
if available, can contribute appreciable amounts of iron to the diet.
The cell walls, the fruit skin, and all structural parts of fruits are made
up of celluloses and hemicelluloses, which are polysaccharides. The pectic
substances which cement or bind the cells together, are found in cell walls.
These polysaccharides are not digested in the human body. However,
these substances do have an ability to imbibe large quantities of water and
get swollen. The food residue is thus softened and passes smoothly through
the intestine.

VEGETABLES

Vegetables are plants or parts of plants that are used as food. The term
vegetable in more narrow sense is applied to those plants or parts of plants
that are served either raw or cooked as part of the main course of a meal.
Vegetables are important in improving the acceptability of a meal, because

179
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

of the innumerable shades of colour, flavour and texture they contribute. A

meal without vegetables and fruits would be very dull indeed.
The parts of plants normally used as vegetables include leaves, roots,
tubers, bulbs, fruits, seeds (beans and peas), flowers, stems and shoots.
Some parts of plants can be grouped under more than 1 heading. The nor-
* mal classification of the parts of plants used as vegetables in the tropics is
given in Table 27.

Table 27. Plant parts used as vegetables in tropics

Leaves Roots and Bulb Fruit Flower Stem and

tubers shoot

Amaranth Beet Garlic Cucumber Agasti Amaranth

Cabbage Carrot Leek Brinjal Broccoli Colocasia stem
Colocasia Potato Onion Drumstick Cauliflower Celery
Fenugreek Potato (sweet) Capsicum Okra Drumstick Lotus stem
Lettuce Radish Kovai Plantain Onion stalk
Mustard Tapioca Papaya Waterlily Knol khol
Radish leaves Turnip Tomato Plantain stem
Spinach Yam All beans Spinach stalk
All gourds

Leafy vegetables
Leafy vegetables are high in water and low in carbohydrates. They con¬
tain 2.7-4.4% protein and very low amount of fat. Their chief contributions
to diet are minerals and vitamins. Leaves in general are important sources
of iron and p-carotene which is provitamin A. Some leafy vegetables may
contain oxalic acid which may interfere in the absorption of calcium present
in the diet. Composition of leafy vegetables (per 100 g edible portion) is given
in Table 28 (Sumati and Shalini Rao, 1993).

Roots and tubers

Roots and tubers in general are good sources of starch. They are poor to
fair sources of proteins, B vitamins and ascorbic acid. Potato is rich source
of starch. Depending on the use of potato in the diet its contribution of
energy to diet varies. It is a fair source of protein, ascorbic acid and B vita¬
mins. Sweet potato is a fair source of ascorbic acid and B vitamins. Based
on its colour, i.e. yellow flesh variety is a rich source of provitamin A; carrots
are rich source of p-carotene and carbohydrate.

Flavour
Vegetables vary widely in flavour. This is mainly because of various
compounds that are present. Volatile sulphur compounds are present in
cabbage, cauliflower and turnip. Allyl sulphide is found in onions and gar¬
lic, an amino acid, S-methyl-C cysteine sulfoxide is also present.

180
 FRUITS AND VEGETABLES

CO CD CD O LO 'cr r^- o LO D- o
CO 00 CO 00
O E 00 cn r^- CD LO CD CM 'Lf
C\l CO
00 00 CM "O'

co CO U0 CO O
I g 00 CD

c
> ^
-2 CD CD CO 1— CO CO o CO — CO LO
O '— 'O' CM o CO o T— CO CM o
o £
JO O o o o o o o o o cb o
cc

°s 'O'
C\J CO LO
00
CD CO CO CO CM o
CM
CO 00 CD 00 LO
CM

< CD O o o o o o CO o o o
o o o OO CM CM CO "0- 'O' h- CO
S S' C\J CD CO LO CD LO CO f'» CO CM t—
CD
£ 5 ub LO' co' LO“ co' cm' o' CO
Table 28. Composition of leafy vegetables

CD
CD
D~- CO CO 'T LO LO o CD CO CM
o CM C\J CO CO '0' -O' 00 "O' U0 CD
CD
o

00 -o~ CO LO 00 -O' CD LO h-
,2 CD
O o o o o o o o

C
0)
CD
OO co o 00 p CO 'O' CD h-
o cb
Iron content rounded off to the nearest whole number; Ca, calcium

CO CO CO 00 'Lf 00 -O' 00
cl

' CD
JO 2 CTO CO U0 'O' CD 00 CD o CO LO
co -o 3 "O' CO CM CM CO CO 00 cb cb CM
O ^

.2 ^ CO 00 CM CO CO LO O CO 00 CO
CO CD CD CD CD CT> CO CO CD CD 00 oo D-

iS
-2
Q. £
co TO
o o
CD
CO £
CO
>
TO £ CD TO
£
TO
CO TO I
CO CO co > o CO £ C
TO
CD CD c
TO I to ■4^ .2 C0 TO TO
CO Q. TO
CO
v_ .§ To _ CO CO CO CO co CO £ £ § CO 2 co 4D
JD CD ~ to CD CD CO CD
JO
-2
o co CO
CO S' -2
.to o
CO
to CO > -2-
to P
> TO > TO
CO CD
CO
to £ I s CO
CD CO TO TO CO CO CO O
-2 co > CO CD
jx :> CD O ® 55
_CD
TO
TO to CO c ■2 -b e — CL ZL CD
CD to CO
CO Q-o Z3
& CD C CO
■^ ^ JxC CD
CD
CD '55 CD co 2 -CZ b 2
CD O
o O C
> CD CO
co co CD Cl
JZ
TO cz II co o £ ■o b 2 o
O
TO JZ
CO TO
CO cz JZ CD -2>
CO -p- To
TO TO CO _ £ CO TO o O
To TO CC cz I o co ■o; -Q QC .2 o i £ o O £
TO
CD CO CD co 'cl b w £ w £ w b CD o
O _J DC CO o < < o o Q
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Pigment
The characteristic colour of raw fruits and vegetable is due to the natu¬
ral pigments i.e. chlorophyll (green), carotene (orange, yellow), xanthophylls
(white), anthocyanins (red, violet, blue). On cooking a green vegetable in
presence of acid it turns olive brown (pheophytin) and in presence of salts it
turns bright green.

Composition
Water content is high in most vegetables, but particularly in greens and
tomato. Water constitutes more than 90% of the edible portion of these
vegetables.
Cellulose, the structural carbohydrate in the cell walls of all plants,
occur in slightly different forms in various parts of plant, e.g. stalk of As¬
paragus, the tip is tender but the cellulose changes to a rather woody mate¬
rial which is considerably tougher at the lower end of stalk.
The cell-wails are cemented with a group of compounds called pectic
substances. In immature vegetables most of the pectic substances present
are in the form of protopectin. Protopectin is converted to pectin in the
mature vegetable and then to pectic acid in over ripe vegetables. As the
transition from protopectin to pectic acid progresses, the vegetable softens,
at least in part as a result of the increased solubility of pectic substances.
Some vegetables such as corn and potatoes contain a high percentage
of carbohydrate in the form of starch. In immature vegetables this carbohy¬
drate is primarily in the form of sugar and it gradually changes to starch as
the vegetable matures. The caloric value of vegetable largely comes from the
carbohydrate content; there is no fat in them and with the exception of the
legumes, there is also little protein in vegetables. Legumes, however, are an
important source of vegetable proteins.

Nutritional significance
The nutritional contribution of different vegetables is sufficiently varied
that means it is wise to serve a variety of vegetables to ensure that all the
necessary nutrients from the vegetable category are included in the diet.
Although most vegetables are low in calories, those containing starch do
provide a useful source of energy (accompanied by significant amounts of
vitamins and minerals). Legumes are a valuable source of vegetable protein.
These proteins are classified as incomplete protein and are enhanced in
their usefulness to the body when they are accompanied by a source of
animal protein, such as milk or cheese. Vegetables are notably low in ca¬
loric value of foods in this food group.
Calcium and iron are the 2 minerals found in significant amounts in
vegetables. Beans, peas, broccoli and greens contain significant amounts of
these essential minerals. Spinach contains an appreciable quantity of cal¬
cium, but the oxalic acid in this vegetable combines with some of the cal¬
cium to form calcium oxalate, an insoluble salt which cannot be absorbed

182
 FRUITS AND VEGETABLES

by the body. Vegetables also help meet the body’s need for sodium, chlorine,
cobalt, magnesium, manganese, phosphorus and potassium.
Carotene and ascorbic acid are abundant in many vegetables. Orange-
coloured vegetables and dark green leafy vegetables are excellent sources of
carotenes. Leafy vegetables are also good sources of ascorbic acid.
Vegetables are useful in the diet because of their high fibre content.
Since fibre is not digested in the body, it is considered as a roughage which
promotes motility of food through the intestines. Though cellulose does not
contribute in a strictly nutritional sense because it is not digested and ab¬
sorbed, its role as roughage is viewed increasingly as an important role in
maintaining good health.
The nutritive value of a particular kind of vegetable is influenced by the
variety of vegetables, the growing conditions, the treatment from the field to
the kitchen, and the method of preparation.

Production and availability

India is one of the largest producers of fruits and vegetables in the
world. About 46.97 million tonnes of fresh fruits and 110.62 million tonnes
of vegetables are grown in nearly 9 million ha, consisting nearly 6% of gross
crop land. India produces a wide range of tropical, subtropical and temper¬
ate fruits and vegetables. (Vikas Singhal, 1999).
After the start of green revolution and attainment of self sufficiency in
food production, the need for food processing was realized. It is estimated
that 30-35% fruits and vegetables worth of about Rs 30,000 million perish
due to want of post-harvest facilities, thus depriving the farmer the fruit of
his labour.
Over the last few decades, both developed and developing countries
experienced many life style changes that have led to an increased demand
for processed foods. Processed foods now represent more than 50% of the
diet of many developed countries. The demand for ready-to-eat foods is in¬
creasing presumably with more and more women folk venturing the out of
house work culture.

Processing, preservation and storage

Drying: Preservation of foods by drying is perhaps the oldest method
known. Large quantities of fruits are dried under the sun in different parts
of the world such as Spain, Asia, Greece, and other Mediterrarean countries,
Arabia and Afghanistan. The modern method of dehydration, i.e. drying
fruits and vegetables under controlled atmosphere is however assuming
importance.
The main objective of drying is removal of free water (lowering of water
activity below 0.7) from fruits and vegetables to the extent, where micro¬
organisms do not survive and reproduce (Desrosier, 1970; Somogyi and
Luh, 1975). Simultaneously, the total solids, viz., sugars, organic acids are

183
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

concentrated, exerting osmotic pressure to inhibit the micro-organisms. Thus

reduction in water content, and packaging, controls the biological and chemi¬
cal forces respectively which act upon fruits and vegetables, facilitating pres¬
ervation of these perishables (Desrosier, 1970). There are many methods by
which drying is accomplished such as sun drying, drum drying, vaccum
drying and freeze drying etc.
Sun drying: Under sun-drying, the sound fruits are loaded on trays, trans¬
ferred to the sun-drying yard and allowed to dry, until the fruits are about
two-thirds dry. Then the trays are stacked in the shade to allow the later
stages of drying, which, proceeds slowly. Apricots, peaches, pears and grapes
are some fruits that are sun-dried (Salunkhe et al, 1976). Among vegeta¬
bles, cucumbers, potatoes, chillies, okra etc. can also be sun-dried.
Lower capital investment is required to apply this simple method. Since
sun-drying depends on uncontrollable factors, production of uniform, and
high-quality product is not expected. Some over drying, contamination by
dust as well as dirt, and insect infestation of the finished product are usu¬
ally tolerated. The most obvious disadvantage of this technique is its com¬
plete dependence on the sun light. Generally sun drying will not allow the
fruit products to dry below 15-20% moisture level. The resulting product
will have a limited shelf-life (Somogyi and Luh, 1975).
Incorporating some improvement in the sun-drying technique, a hot
box process, which improved the product by reducing contamination by
dust, insect infestation and animal or human interference was developed in
Syria (Szulmayer, 1971a, 1971b). It reduced the drying time to half the
usual time, and the finished product had more appealing appearance and
better flavour than that dried in the conventional way. Szulmayer (1971a,
1971b) has also described an indirect solar drying process, in which the
product is exposed to heated air, rather than to direct sun. Use of hot air
reduces relative humidity of the air, thereby resulting drying at a reason¬
able rate. Solar drying (Fig.33 top) with chimney effect improves the quality
of the finished products (Pawar etal, 1988; Khurdiya and Roy, 1986).
Cabinet drying: Food products dried in a cabinet dryer are placed on trays
and moved into a drying compartment where the product is exposed to the
drying air. This management is illustrated in Fig. 33 bottom).
Drum drying: One of the novel products developed from mangoes is fruited
cereal, viz. mango cereal flakes, which is prepared from mango pulp by
drum drying. Mango pulp is blended with a small quantity of edible starch,
and the blend adjusted for acidity and pH and then fed on to the heated
revolving stainless steel double drum roller drier. Other products like tomato
flakes, strained baby foods, guava etc. can also be dried by the above tech¬
nique.
Vaccum puffing and dehydration: The puffing unit consists essentially of a
shallow receptacle with an air-tight lid, connected through a quick opening
valve to a vaccum reservoir maintained at 62 cm Hg vaccum. The lid of the

184
 FRUITS AND VEGETABLES

Fig. 33. Top. Solar dryer (Source: Khurdiyar, 1989); bottom, schematic presentation of a cabinet dryer:
1. circulating fan, fully reversible; 2. heater batteries; 3. vented air inlet ports; 4. vented air
exhaustports; 5. adjustable louver walls; 6. truck space (Source: Forrest, 1968)

receptacle can be closed and opened instantly by a pneumatic cylinder,

which open by the suction from the reservoir. The entire operation of trans¬
ferring trays to the receptacle, closing the lid, applying and releasing the
vaccum and opening the lid, can be completed within 15 sec. The puffed
porous pieces can then be dried in a tunnel (or drier) at about 66°C with an
air velocity of 300 m/min. The product has excellent consumer acceptance
(Pawar et al, 1988).
Foam-mat drying: The foam-mat drying process consists essentially of in¬
corporating small amount suitable foaming agents such as glyceryl-mono-

185
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

stearate, egg albumin, groundnut protein isolate, guar, guava and

carboxymethyl cellulose into the fluid food materials, so that they can be
whipped to a low density foam and spread on trays. Drying is done at rela¬
tively low temperatures, in an ordinary forced air-circulation drier. The dried
product can be reconstituted readily. The method is considerably cheaper
than puff drying, drying, drum drying, etc.
The foaming agent, dissolved or dispersed in a small quantity of water,
added to the fruit juice concentrate or pulp, mixed in waring blendor and
then foamed in a Hobart mixer fitted with a wire mesh. The foamed material
extruded into strips, 3-4 mm in diameter, and the strips spread on stain¬
less steel trays. The trays were arranged in a cabinet drier maintained at
65°C to 70°C in such a manner that the strips were parallel to the flow of
air. The material dried in 30-60 min. depending on its nature. The dried
strips were scraped from trays and filled into air-tight containers as they
were hygroscopic. The optimum amount of the foaming agent to be used is
0.3-1.5%. The strips could be dried crisp in 30-45 min.to a moisture con¬
tent of 1.5-2.0%. The foam-mat drying technique could be successfully em¬
ployed in variety of fruit pulps, concentrates and similar products by
standardizing the conditions in each case.
Evaporating cooling—cool chambers: Evaporative cooling is Nature’s very own
method. Evaporation of water produces a considerable cooling effect and
the faster the evaporation the greater the cooling. Evaporative cooling oc¬
curs when air, that is not already saturated with water vapour, is blown

186
 FRUITS AND VEGETABLES

across any wet surface. Thus evaporative coolers consist of a wet porous
bed through which air is drawn and is cooled and humidified by evapora¬
tion of water. Theoretically, the lowest temperature, that can be reached by
the evaporation of water is the wet tube temperature (Hall, 1975). Evaporative
cooling is widely used for comfort cooling of living and working spaces in
hot, dry climates and it has a considerable potential for pre-cooling and
even storage of fruits. The principles of evaporative cooling can be gainfully
utilized for storage of fresh produce, particularly in rural India, as it can be
constructed even in a remote village (Fig. 34).
Freeze drying: In this method, the material such as fruit juice concen¬
trate, is first poured on trays in the lower chamber of a freeze drier and the
frozen material is dried in the upper chamber under high vacuum. The
material is directly dried by sublimation of ice without passing through in¬
termediate liquid stage. The dried product is highly hygroscopic. It reconsti¬
tutes easily. Mango pulp, orange juice concentrate passion fruit juice and
guava pulp have been prepared, to give freeze-dried powders of excellent
quality for taste, flavour and reconstitution property, etc.
Acclerated freeze drying: This method which is an adaptation of the freeze
drying technique has been developed to a commercial process by the Aberdeen
workers for drying fish, meat, etc., to meet Defence Services demands. On
account of low temperature employed for drying and the technique of drying
the pieces of the product without unduly disturbing their shape and taste
the dried material has good reconstitution properties and possesses exact
taste and flavour, and as such, has been well accepted by consumer. Dried
products are highly useful in the preparation of emergency food products
and rations for use by the Defence Services under difficult and adverse
conditions of climate and terrain such as high altitudes and mountain areas.
In this method, the pieces of material to be dried are kept between 2 perfo¬
rated or wire mesh trays, inside a cabinet freeze drier. As the material dries,
the pieces are gradually reduced in bulk by reducing the clearance between
the 2 trays hydraulically, with the result the dried material retains its normal
shape and regains it when rehydrated. This is a highly important considera¬
tion in the drying of meat, fish and semi-solid pieces of food. The equipment
needed for large-scale freeze drying of foods is highly costly. In view of the
several advantages, however, the Government of India has set up a 5 tonne
capacity unit for meeting the needs of the Defence services stationed at high
altitudes and on difficult terrains (Pawar et al, 1988).
Dehydro-freezing: In this method, the product is first dried partially and
then frozen, and is thus slightly different from the usual freeze drying tech¬
nique.
Canning: For canning, fruits and vegetables should be absolutely fresh.
An hour from the field to the can is the accepted ideal. The fruit should be
ripe but firm, and evenly matured. It should be free from all unsightly blem¬
ishes, insect damage, and malformation. Over-ripe fruit is generally infected
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

with micro-organisms, and would show poor quality. Under-ripe fruit will
generally shrivel and toughen on canning. The vegetables should be tender,
except that tomatoes should be firm, fully ripe and deep red. They should be
rasonably free from soil, dirt etc. The main processes of canning are de¬
scribed below (Girdharilal etal, 1986).
Sorting and grading: After preliminary sorting, the fruits and vegetables
are graded. This is necessary to obtain uniformity in size, colour, etc. and is
done by hand or with grading machines. There are several mechanical grad¬
ers, viz. screen graders, roller graders, rope or cable graders. Fruits like
berries, plums, cherries and olives are graded whole, whereas peaches, ap¬
ricots, pears, mangoes, etc. are generally graded after cutting them into
halves or slices.
Washing: The graded fruits and vegetables are washed with water in
different ways, such as soaking or agitating in water, washing with cold or
hot water sprays. A thorough wash is most essential for good results. Veg¬
etables may preferably be soaked in a dilute solution of potassium perman¬
ganate to disinfect them. Agitation of the washing water is effected generally
by means of compressed air or a force pump or a propeller type equipment.
Spray washing is, however, the most efficient method.
Peeling, coring and pitting: The washed fruits and vegetables are prepared
for canning by peeling, coring, blanching etc. Fruits and vegetables are peeled
in a variety of ways by: (i) hand or with knife, (ii) machine, (izi) heat treatment,
and (iv) by lye solution. Cores and pits in fruits are removed by hand or by
means of machine.
Hand peeling: Many of the fruits and vegetables are peeled and cut by
hand using special knives. The peeling knife with a qurved blade and a
special guard to regulate the depth of peeling is of special interest, as it can
be used universally for many fruits and vegetables.
Peeling, coring, and pitting by machine: Recently mechanical peeling,
coring and cubing machines for pear, apple and other fruits and vegetables
have been introduced. There are also automatic machines for peache and
cherry. Mechanical peelers are used for root vegetables carrot, turnip, po¬
tato etc.
Peeling by heat: Some fruits and vegetables, particularly certain varie¬
ties of peach and potato, are scalded in steam or boiling water to soften and
loosen the skin which is subsequently removed easily by hand. The latest
development of this method consists in exposing fruit or vegetable to a high
temperature (105°CJ for 10-60 sec. whereby the skin bursts and retracts
facilitating its easy removal by means of pressure sprays. On a large scale,
a furnace fitted with variable speed conveyor and temperature-control de¬
vice is used. To get good results, fruit or vegetable should be of uniform size
and maturity. It is claimed that in this method, there is little loss of flavour,
and the product is of uniform colour free from any blemish. The heat peeled
fruit absorbs sugar more readily than fruit peeled by other methods.

188
 FRUITS AND VEGETABLES

Lye peeling: Fruits and vegetables like peach, apricot, quince, sweet
orange, carrot and sweet potato are generally peeled by dipping them in
boiling caustic soda or lye solution of 1-2% strength, for short periods rang¬
ing from 30 sec. to 2 min. (depending on nature and maturity of fruit or
vegetable). The strength of the boiling lye is adjusted from time to time. The
hot lye loosens the skin from the flesh underneath. The peel is then re¬
moved easily by hand. Any trace of alkali is removed by washing fruit or
vegetable thoroughly in running cold water or preferably by dipping it for a
few seconds in a very week solution of hydrochloric or citric acid. This method
is quick and reduces wastage as well as cost of peeling.
The lye-dipping equipment varies from a simple open iron pan. In the
lye solution, with iron baskets or cages for holding the fruits or vegetables,
to fully automatic machines. The use of aluminium in the lye dipping equip¬
ment should be avoided as it reacts with sodium hydroxide. Recently, stain¬
less steel equipment has been introduced for lye-peeling of fruits such as
rough segments, peaches etc.
Blanching: Treatment of fruits and vegetables with boiling water or steam
for short periods followed by cooling prior to canning, is called blanching.
This loosens skin, and the process is particularly important in beetroot and
tomato. It facilitates close filling in the can and drives out air from tissues.
Further, it helps clean the fruit or vegetable and to eliminate micro-organ¬
isms. It also inactivates the enzymes, thus preventing the possibility of
discolouration. By removing undesirable acid elements and astringent taste
of the peel, it also improves the flavour.
In a small cannery, the fruit or vegetable to be blanched is placed in a
wire perforated basket, which is first dipped in hot water for a short period,
ranging from 2 to 5 min. and then dipped in cold water. Hard water should
not be used for blanching, as it toughens the tissues and destroys the natu¬
ral texture. In large canneries, blanching is done on belt conveyors passing
through boiling water or steam, or in a rotary horizontal cylinders.
Can filling: The cans are washed with water or subjected to a steam jet
to remove any adhering dust or foreign matter. In large canneries, the cans
are washed with jets of compressed air or water. In our country where the
canning industry has not developed so much as to warrant the use of costly
machines, using an empty can in open tanks containing hot water is the
usual practice. In some factories, however, simple devices have been made
to sterilize the cans in steam, before use. Plain cans are used generally,
although in the case of coloured fruits like red plum, black grape, straw¬
berry, it is desirable to use fruit-lacquered cans. Automatic can filling ma- 1
chines are in use in large canneries in many countries, but choice graded
fruits are generally filled by hand to prevent bruising and also ensuring
properly graded pack. In India, filling by hand using rubber gloves is a
common practice.
Syruping or brining: The cans are filled with hot sugar syrup for fruits

189
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

and with hot brine for vegetables. Addition of syrup or brine improves the
taste of the canned product. The syrup or brine should be poured to the can
at 79°-82°C, leaving suitable head space ranging from 0.32 cm to 0.47 cm
in the can and closed on the double seaming machine.
In some of the large canneries in other countries, syruping or brining is
done on automatic machines. These machines are available in various de¬
signs and of capacities. A simple syruper consists of a 227-litre capacity
tank of stainless steel or aluminium metal fitted with a closed steam pipe
inside and provided with a delivery valve for filling the cans. The cans travel
on a continuous belt in an inclined position below the syrup pipe and get
filled, the overflowing excess syrup is pumped back into the syrup tank by a
centrifugal pump.
Lidding or clinching: Formerly, the cans after being filled, and covered
loosely with the lid and passed through the exhaust boxes for large-scale
practice. This had certain disadvantages such as spilling of the contents
and toppling of the lids. Lidding has now been modernized, the clinching
process in which the lid is partially seamed to the can by a single first roller
action of a double seamer. The lid remains loose to permit the escape of
dissolved as well as free air from the contents and also the vapour formed
during the exhaust process. Counting and coding devices are also generally
incorporated in clinching machine.
Exhausting: Before sealing the cans finally, it is necessary to remove all
air from the contents. The process by which this is achieved is known as
'exhausting’. By removing air from the containers, risks of contamination of
the tin plate and pinholing during storage, as also of discolouration of the
product, are reduced, because oxidation is prevented. The temperature of
syrup or brine in the can should be 79°-82°C. Removal of air also helps
better retention of nutrients especially of vitamin C. Since some of the fruits
and vegetables have a tendency to expand or shrivel during heating, the
exhaust process will help in avoiding over-filling or under-filling of the can.
For instance, corn and pea expand when boiled in brine and strawberry
shrivel when heated in sugar syrup. The other advantages of the exhaust
process are prevention of bulging of the can when stored in hot climates;
reduction of chemical reaction; and prevention of excessive pressure during
sterilization. Fruits and vegetables sometimes react slowly with the metal of
the can producing hydrogen gas which builds up pressure. If there is no
vacuum inside the can to start with, bulging will take place and before the
marketability of the canned product would suffer. Vacuum in the can, after
exhaust, depends on several factors, viz. as the time and temperature of
exhaust the headspace in the can etc. The higher the temperature of ex¬
haust, the more the volume of water vapour formed, and consequently the
greater the vacuum inside the can. It is, however, preferable to exhaust the
cans at a temperature for a longer time to secure uniform heating. The
headspace left after filling the can affects the vacuum; the smaller the

190
 FRUITS AND VEGETABLES

headspace the greater the vacuum. A can sealed at a lower altitude will
show a lower vacuum than at a higher altitude and vice versa. Cans with a
low vacuum generally become springers at high altitudes.
Containers are exhausted either by heat treatment or by mechanical.
The heat exhaust method is generally used in the case of cans.
Sealing: After exhausting, the cans are sealed by special electrical ma¬
chines known as double seamers. These are of various designs and capaci¬
ties. These are hand-operated, semi-automatic and fully automatic seams.
In sealing lids on metal cans, a double seam is created by interlocking
the curl of the lid and flange of the can. Glass containers are sealed under
vacuum created mechanically or by steam-flow. The containers are sealed
with a close-fitting cover of tin plate or a thread or long cap (Luh and Woodroof,
1975).

Processing
The term processing as used in canning technology, means heating or
cooling of canned foods to inactivate bacteria.
Heat-processing: The heat treatment to which foods are subjected after
hermatic (air tight) sealing in containers is called heat process. The tem¬
perature and time of processing vary with the nature of the product and the
size of the container. Acid products with pH values below 4.5 are readily
preserved at the temperature of boiling water. The containers holding these
products are processed in atmospheric steam or hot-water cookers.
Non-acid products require higher temperatures for sterilization and are
processed in steam-tight pressure cookers—retarts or in continuous pres¬
sure cookers—usually controlled by automatic devices. In general, length of
the process depends on the processing temperature; the higher the tem¬
perature the shorter-time required. The characteristics of products cause
differences in processing requirements. A viscous liquid will require longer
processing time than a less heavy liquid. The size of the can is an important
factor in determining the correct combination of time and temperature in
processing. Obviously, heat will penetrate the centre of a small can more
quickly than to the centre of a large one. Since it is vital for convey type of
product, precise information about the rate of heat penetration is required.
Recently the flame sterilizer has been developed for certain products in
which the cans are exposed to direct flames while rotating. It is a high-
temperature short-time process in which the sealed containers are heated
by means of direct contact with flames while rotating rapidly (Luh and
Woodroof, 1975).

Cooling
After the process containers are cooled quickly to prevent over-cooking.
This may be done with water in the cooker under air pressure or by convey¬
ing the containers from the cooker to a rotary cooler with a cold-water spray.
Cooling water may be kept sterile with 1-2 ppm chlorine.

191
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Labelling and casing

After cooking, cooling and drying the containers are ready for labelling.
Labelling machines apply glue and labels in a high-speed operation. The
labelled cans or jars are conveyed to devices which pack them into shipping
cartons. The typical vegetable canning operations are given in Fig. 35.

!>• 'll*

mzz.
. •>
Harvesting Receiving raw product
Soaking and washing

Sorting and grading

Blanching rrfi
Peeling and coring

Exhausting
Sealing
Processing

Cooling Labelling Warehousing and

packing

Fig. 35. Typical canning operations

192
 FRUITS AND VEGETABLES

Dehydration and concentration

Dehydration is probably the oldest method of preserving fruits and veg¬
etables. Removal of water from foods is primarily accomplished by applica¬
tion of heat, but new methods employing other sources of energy are being
used (Charman, 1971; van Arsdel et al, 1973). Foods are dehydrated to
protect against spoilage by micro-organisms and to reduce the cost of pack¬
aging, handling, storing and transporting. There are several methods of
drying used industrially, viz. forced air drying, drum-drying, spray-drying,
vacuum drying, and freeze-drying. Continuous belt-conveyor drying has in¬
creasingly replaced tray and tunnel dryers in recent years.
Mechanism of dehydration
As water evaporates from the wet fruit or vegetable surface, the diam¬
eter of superficial water-filled pores and capillaries diminishes and solid
structural elements pull closer together under the influence of surface ten¬
sion. The effect spreads into deeper layers of tissue and eventually all the
way to the centre. Value shrinkage is substantially equal to the volume of
water evaporated, and the drying rate per unit of surface remains constant.
A wide variety of dried fruits and vegetables is now on the retail market,
and many more are dried for re-manufacturing purposes. For example, most
of the dehydrated garlic and onion are used as seasoning for such products
as canned tomato, tomato ketchup, tomato sauce and soups. Dehydration
is also being used to convert waste materials into animal feed. Solids from
tomato-processing plant, for example can be dried and incorporated into
animal feed.

PROCESSED PRODUCTS

Preparation of fruit jam

Jam is prepared by boiling the fruit pulpcwith sufficient quantity of
sugar to a reasonably thick consistency, firm enough to hold fruit tissues in
position. It should contain not less than 68.5% soluble solids as determined
by a refractometer, when cold and uncorrected for insoluble solids. Jam
may be made from a single fruit or from a combination of two or more fruits.
The preparation of jam requires several operations.
Selection of fruit
Ripe fruit having good colour, flavour and aroma should be selected. If
the fruit is firm and tough, allow it to stand for a day or two to develop
sweetness and flavour. Unripe or immature fruits should not be used for
this purpose. Wash the fruits thoroughly in fresh water. Remove stems and
leaves, if any. Trim the bruised and blemished portions.
Preparation of fruit
Peel the fruits. Remove any stone or core of the fruits. Cut the fruit into

193
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

small pieces. If the fruit is tough and hard, boil it with small quantity of
water to soften it.
Addition of sugar
To the sour fruits, add an equal quantity of sugar by weight. Add only
three-fourths sugar by weight to the sweeter varieties. To ensure a mini¬
mum of 68.5% of total soluble solids (TSS) in the jam, generally 24.9 kg
sugar is required for every 20.4 kg fruit taken.
Addition of acid
Generally citric, tartaric or malic acid which are natural fruit acids are
used to supplement the acidity of the fruit for making jam. Addition of acids
to the fruits, deficient in it, is a necessity because appropriate combination
of pectin, sugar and acid is essential to give a 'set’ to the jam. The acid
(0.2-0.4%) is added @ 1.5 to 2 g/kg fruit.
Mixing
Mix the ingredients thoroughly and allow the mixture to stand for % to
1 hr, so that the sugar dissolves in the juice released from the fruit.
Cooking
Cook the mixture slowly with occasional stirring and crushing, till the
temperature reaches 105.5°C (at sea-level) or till the cooking mass approaches
the desired consistency. When the mass is sufficiently thick in consistency,
dip a spoon into it and if the product runs-off the sides of the spoon, and on
cooling, the product falls off in the form of a sheet (detailed under sheeting
or ladle test) instead of flowing readily in a single stream, it means that the
end point has been reached and the product is ready for filling into containers.
Otherwise continue boiling till the sheet test is satisfactory.
Filling and closing
Fill the hot jam into clean dry jars placed on an insulating material like
a wooden board or a thick pad of cloth (for preventing the breakage of glass
jar). Close the filled jar without delay. Only permitted edible food colours
should be added; if necessary, and these should be added at the end of the
boiling process. Ordinarily, jams do not require the addition of flavours. If
desired, they may be added towards the end of tie boiling process.
Cooling and storage
Allow it to cool and store in a cool dry place.
Precautions
Following points must be considered for getting goods results.
• Pectin present in the fruit gives it a good set.
• High concentration of sugar facilitates preservation.
• Over-ripe fruit should not be used as it produces pasty product.
• In cases where the fruit is deficient in pectin, pectin from other
fruits or commercial liquid or solid pectin may be added.
• If the sugar is in excess, jam becomes sticky and gummy. There¬
fore, add pectin or acid or both to counteract the effect of excess
sugar.
• If sugar is less, add sugar. 1
 FRUITS AND VEGETABLES

• Under exceptional conditions, where more sugar is not added, it

would be advisable to add small quantity of sodium bicarbonate to
reduce the acidity and thus prevent pre-coagulation.
• Finished product should contain 68.5% total soluble solids by
refractometer 0.52% acidity (citric acid) 64% inversion degree.

Determination by sheeting or Ladle test

This is known as bold plate’ test, the ‘sheet’ or the ‘flake’ test.
Cold plate test
A drop of the boiling juice from the pan is placed on a plate containing
water and allowed to cool. If the jam is about to set, the mixture on the plate
will rinkle when pushed with a finger. The main drawback in this method is
that while the drop on the plate is cooling the jelly mixture continues to boil
in the pan with the result that there is risk of over-cooking the product or of
missing the correct setting point.
Sheet or flake test
This test is more reliable than the plate test. In this test, a small portion
of the jelly is taken with a large spoon or wooden ladle, cooled slightly and
then allowed to drop off. If the jam drops like a syrup, it requires further
concentration, but if it falls in the form of flake or sheet, the end point has
been reached. After some experience this test can be adopted as a routine
measure in the boiling of jam.
Determination by weighing
Where there is some difficulty in handling the thermometer or in un¬
derstanding the sheet or flake test, the weighing method is useful. In this
method, the boiling pan is weighed before, and again after, transferring the
fruit extract and sugar into it. The weight of the finished product should be
about 1.5 times the weight of sugar used. The end point of boiling is deter¬
mined by weighing the pan with the boiling jam.

Jelly
In jelly making, pectin is the most essential constituent. Pectin is present
in the cell-walls of fruits. Its quantity, however varies with the kind of fruit
and even with the variety of the same fruit. Some fruits are rich in pectin as
well as acid and are thus suitable for jelly making.
Selection of fruits
The fruits should be sufficiently ripe, but not over ripe and they should
have good flavour. Slightly under ripe fruit yields more pectin than fully ripe
fruit. On ripening the pectin present in the fruit decomposes to pectic acid,
which does not form a jelly. After picking, the fruits should be used, without
undue delay, for jelly making.
Preparation of fruits
Fruits are washed thoroughly with water to remove dirt. If the fruit has
been sprayed with lead or arsenical sprays, it should be washed in a warm
solution of 1% hydrochloric acid and then washed in water. Fruits are cut

195
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

(in the case of oranges and lemons, it is necessary to remove the outer
yellow portion of the peel to remove the bitterness) into thin slices so that
the acid and pectin in them can be extracted easily.
Extraction of pectin
Only minimum amount of water should be added to the fruits for ex¬
traction of pectic. In grapes, water is not added and fruit being heated in its
own juice.
Test for pectin
Alcohol precipitation test is very simple, quick and highly useful. Find¬
ing the viscosity of the pectin solution by using a jel meter is another method.
Effect of metals
For boiling fruit juice, copper and iron kettles should not be used. Alu¬
minium equipment is satisfactory. The best equipment made from stainless
steel or enamel material or glass.
Straining and clarification
The pectin can be clarified by passing it through cheese cloth and al¬
lowed to settle overnight and the supernatent liquid drained off.
Pectin requirement
Usually 0.5-1.0% pectin of suitable quality in the extract is sufficient to
produce a good jelly.
Essential constituents of a good jelly
Pectin : 1.0%
Sugar : 60-65%
Acid : 1.0%
Water : 33-38%
The rate of formation of jel is influenced by concentration of pectin in
the solution, constitution of pectin, hydrogen ion concentration (pH of the
pectin solution), concentration of sugar in solution, temperature of the mix¬
ture.
Foaming
Foaming of the jelly during boiling can be controlled by adding to the
pan a small quantity of edible oil. Generally 1 teaspoon of the oil is sufficient
for a batch containing 45.3 kg sugar.

Cloudy or foggy jellies

Cloudy jelly: This type of jelly is formed if the juice or extract not clarified.
Use of immature fruits: Green, immature fruits contain starch which is
insoluble in the juice, and the jelly made from them has, the cloudy appear¬
ance.
Over-cooking: Over-cooked jellies are gummy and sticky, on account of
their excessive viscosity, they do not become clear after they are poured into
containers.
Over-cooling: When the jelly is cooled too much, it becomes viscous and
sometimes lumpy. Such a jelly is almost cloudy.

196
 FRUITS AND VEGETABLES

Faulty pouring into containers: The jelly should not be poured in containers
from a great height because air gets incorporated into the mass and the
bubbles formed do not clear easily, especially when the jelly is well made
and sets within a short period. The spout of the pouring vessel should not
be more than about 2.5 cm from the top of the container.
Non-removal of scum: The jelly becomes cloudy also when scum is not
removed before pouring.
Premature gelation: If there is excess of pectin in the juice, it causes pre¬
mature gelation with the result that air may get trapped and make the jelly
opaque. This can be avoided by using low pectin.
Formation of crystals
The formation of sugar crystals in a jelly is caused by adding excess
sugar. It is also an indication of over-concentration of the jelly.
In making a jelly from fruits deficient in acid, the mixture should be
boiled for a few minutes after adding the sugar so that the sugar is dissolved
adequately and it does not crystallize later.
Crystals of cream of tartar sometimes separate out in grape. Although
they are harmless, they spoil the appearance of the jelly. The cream of tar¬
tar should be eliminated from the grape juice by allowing settling of the
juice, and the treated juice only used for making the jelly.
Syneresis or weeping
The phenomenon of spontaneous exudation of fluid from a gel is syneresis
or ‘weeping’ of jelly. It is caused by several factors such as excess of acid, too
low concentration of sugar or soluble solids and insufficient pectin.

Fruit juices and fruit syrups

The consumption of unfermented fruit juices and fruit syrups which
have been preserved in sealed bottles or cans is very great in many coun¬
tries, particularly in the USA and Germany. Their preparation and preser¬
vation are many-sided operations, varying according to the nature of the
fruit and the type of product required. World trade (imports) in fruit juices
and concentrates reached $4.36 billion in 1993, indicating a drop from the
1992 figure of $5.17 billion but an increase over the $3.97 billion of 1989.
The fluctuations during 1989-94 period reflect not only changes in qualities
imported but also movements in price levels and foreign exchange rates.
The volume of juices traded internationally increased by more than 10%
from 1992 to 1993 (Oleson, 1996). Briefly, fruit juice may be considered
under the following headings.
Fruit selection for juice
As a rule, fruits for juice production should be fully ripe and of good
colour and flavour, but over-ripe, rotten, mouldy or diseased fruit should
not be used. In some cases, eg. apples, juice-making is an outlet for fruit
which, although sound, is not of marketable quality, i.e. it may be small.
With apples also, the colour of the fruit is of little consequence, but the

197
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

blending of different commercial varieties to obtain a juice of the right de¬

gree of sweetness may be desirable. Selection and blending demand consid¬
erable skill and judgment.
Juice extraction
Mechanical details of extraction, are not given here as these must be
adapted to the structure of the fruit. In general, the aim is first to disrupt
the cells of the juice-bearing tissues so as to release the juice, and secondly
to press the juice out. In apples, soft fruits, berries, etc., the whole fruit is
milled or grated and then pressed in hydraulic or screw presses. In citrus
fruits the rinds contain bitter substances which must not be allowed to
contaminate the juice proper; and the same applies to pomegranate rinds,
which are very astringent. For citrus fruits extraction is carried out by re¬
volving burrs or reamers on which the transversely-halved fruits are pressed;
for pomegranates and pineapples special presses, cutters and mills have
been designed to make the best use of all edible portions. In the case of ripe,
soft fruits, berries, in the raw state, the juice contains soluble pectin and
small quantities of other colloids which may make it slimy and difficult to
press out from the tissues after milling; moreover, with many fruits, even if
the juice can be expressed, the soluble pectic substances quickly form first
gels and, finally, flocculent precipitates which carries down all suspended
particles and insoluble colouring matters and completely changes the char¬
acter and even the flavour of the juice. To prevent this and to render filtra¬
tion easy, the milled material is treated with an enzyme (pectinol in the
USA, Filtragol in Europe) produced from the growth of moulds or bran,
which converts the pectins partly into soluble reducing sugars and partly
into insoluble pectic acid. The enzyme works best at pH 3.0-3.5 and, under
ideal conditions, it should completely remove the pectin in twenty-four hours.
Juice treated with enzyme should be heated to 170°C for 30 min. to
inactivate the enzyme and prevent further sedimentation. No doubt flash¬
heating at a higher temperature would have the same effect.
Deaeration
Deaeration of juices should be completed as early as possible in the
preserving process, particularly in citrus juices and tomato juice which de¬
velop off-flavours and lose vitamin C very rapidly through the action of oxi¬
dizing enzymes or even by chemical oxidation. They recommend precautions
against incorporating air in the juice during extraction, and they carry out
the actual deaeration either by spraying the juice into a chamber under
vacuum or by allowing it to enter the vacuum chamber as a thin film travel¬
ling over baffles. A vacuum of 70 cm removes 95% of the dissolved air and is
effective in preventing oxidation.
Straining, filtering and clarification
Clarification is essential to produce bright and sparkling fruit juices,
and it may considerably reduce the flavour of the juice. Moreover, with juices,
which owe their colour to insoluble coloured bodies (e.g. tomato, apricot)

198
 FRUITS AND VEGETABLES

over-filtration will cause decoloration. The modern tendency is to produce

juices containing a proportion of suspended matter consisting of fragments
of tissue, e.g. orange and lemon juice-sacs, but not of precipitated pectic
substance. For this purpose, the juice is merely coarsely screened or strained
and sold in that condition—usually in cans or opaque glasses.
For the production of clear juice several types of filters are available
according to the degree of clarity desired. The simplest is the bag filter of
flannel or cloth which removes all the larger fragments, while for greater
clarity and output there are paper-pulp filters to produce a perfectly clear,
bright product. High-speed centrifugal separators are used in the produc¬
tion of clear fruit syrups and, for some purposes, recourse is had to the
addition of finings of casein, gelatin and tannin, or even Bentonite clay.
A certain degree of clarification can be effected by heating, which causes
some coagulation of colloidal substances. Heating also stabilizes the juice
by destroying the pectic enzymes, although some deposition of pectic sub¬
stances may be expected even with heated juices after prolonged storage. In
the case of apple juice which contains starch, starch-splitting as well as
proteolytic and pectin-splitting enzymes are used in clarification.
Sterilization and preservation
Pasteurizing: The fresh-fruit flavour on which much of the value of fruit
juices depends is readily impaired by cooking, the degree of impairment
being a function of time and temperature. Hence pasteurization is either
carried out for a very short time at a high temperature (flash-pasteurization)
or for a longer time at a lower temperature. The times and temperatures
recommended depend, in both cases to some extent, on the pH of the juices.
Tressler et al (1939) described several types of flash pasteurizers. These
usually consist of tubes, often ribbon-shaped, through which the juice passes
and which are heated either by steam or hot water. When the juice has
reached the required temperature for sterilization and enzyme destruction
it is cooled quickly to the temperature for filling into cans or bottles, by
passage through a cooling coil. Temperature control can be effected by varying
the temperature outside the tubes, by altering the rate of flow of juice and,
to a lesser extent, by altering its initial temperature. Rapid sterilization and
cooling of liquids, even when packed in cans, is possible if the cans are
either rolled or rapidly rotated in the cooker and cooler. Tressler et al. (1939)
stated that the time and temperatures required to destroy pectic enzymes in
citrus fruits are 4 min. at 85°C, 1 min. at 87.78°C, or a fraction of a minute
at 90.56°C. Filling temperatures for cans of pasteurized juice are of the
order of 76.67-82.2°C. Bottles can also be filled at 82.20°C but should be
warmed before hand and cooled more slowly than cans; if juice is pasteur¬
ized in bottles it should be heated and cooled more slowly than in cans.
Some manufacturers, having deaerated the juice, take precautions to ex¬
clude air during pasteurization and cooking, e.g. by the use of inert gases,
vacuum sealing, etc. This is said to preserve the full bouquet of the original
juice.
199
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Filtration: The Seitz-Boehi process of removing micro-organisms by fil¬

tration has been in use for apple juice on a commercial scale in Germany
very successfully for several years. About 0.1% of Filtragol is added to the
freshly expressed juice and, after 24 hr, the sediment is removed in a cen¬
trifuge and the juice roughly filtered through clarifying discs. The filtrate is
then impregnated with carbon-dioxide at 8 kg/cm2 to prevent the growth of
yeasts or bacteria and stored in large enamel-lined steel cylinders, holding
up to 45,460 litres, until required for bottling.
Bottling is carried out in a sterile manner with full bacteriological pre¬
cautions. The carbon-dioxide is removed and the liquor rendered brilliant
by passing through Seitz clarifying discs and goes through the Seitz sterilizing
filter which holds back all micro-organisms. Bottles, caps, filling machines;
in fact, all surfaces with which the juice comes in contact after leaving the
filter are sterilized, usually with 2% sulphurous acid, and scrupulous clean¬
liness, air-filtration, etc. are practised. The juice is usually bottled in the
still condition, but sealing under carbon-dioxide at 1.40 kg/cm2 may be
used as an extra precaution against fermentation.
The addition of preservatives: About 600 parts per million of sulphur dioxide
in citrus juices stored in bulk for subsequent bottling or syrup-making (the
syrups are made by stirring the requisite amount of dry sugar in the cold,
filtered juices until dissolved). For syrups containing 35-50% of sugar
200-300 parts per million of sulphur dioxide are usually added as potassium
meta-bisulphite, calcium bisulphite or sulphurous acid.
Benzoates have become unpopular as preservatives for fruit juices be¬
cause it is believed that they permit colour deterioration, especially in citrus
juices. Tressler etal (1931), however, stressed the necessity for using sodium
benzoate of high purity and stated that the deterioration is rather due to
oxidation than to any action of the benzoate. If the juice is thoroughly
deaerated and stored in the absence of oxygen, 0.05-0.1% of benzoate will
preserve it effectively and impart less undesirable flavour than sulphur di¬
oxide. It is suggested that combinations of sulphurous acid and benzoate .
would be satisfactory, the sulphurous acid to retard oxidative changes and
the benzoate to suppress spoilage organisms. Like sulphurous acid, sodium
benzoate is most effective at high acidity; in fact, it is of no use with non¬
acid products.
Cold storage: Like the fruits, fruit juices can be also preserved satisfacto¬
rily either raw at -17.8°C or at higher temperatures, between -10°C and
-6.7°C if previously heat-treated. Exclusion of air during cold storage helps
preserve the quality of the juice.

Other methods of preservation oligodynamic processes

These depend on the alleged destruction of micro-organisms by minute
traces of certain metals, e.g. silver. In the Matzka process the juice is al¬
lowed to flow in the annular space between 2 metal tubes insulated from

200
 FRUITS AND VEGETABLES

one another. One tube is of silver and the other of aluminium or stainless
steel. The system is heated by hot water, and it is claimed that a small
electric current flowing in the liquid between the 2 metals carries silver ions
which sterilize it. In the opinion of some of the research workers, the steri¬
lization is like a flash pasteurization, although it is true that small traces of
silver are present in the juice. The amount of silver can be varied under
suitable conditions. Its concentration of 0.25-1% part per million is said tp
be sufficient for sterilization.
Schoop process: (Swiss) it is claimed that a simple antioxidation treat¬
ment effectively suppresses the action of yeast and eliminates the need for
high-pressure storage in steel tanks.
Carbonation: Apart from the effect of high-pressure carbonation in sup¬
pressing fermentation, carbonation also renders many juices more refresh¬
ing and palatable. For bottling or canning purposes 2-3 volumes of carbon
dioxide are usually added; in terms of pressures, Cruess and Irish (1940)
recommended 13.61-18.14 kg at 10°C.
For fruit juices low-pressure-low-temperature carbonators are preferred,
the juice being cooled to about 0°C before being charged with carbon diox¬
ide in glass-lined, steel tanks. This method gives a product of uniform gas
pressure and simplifies bottling operations. If the juice only contains 2 or 3
volumes of gas pasteurization can be carried out at ordinary temperature in
sealed cans or bottles.
High-pressure carbonators which charge at higher temperatures can
also be used for fruit juices, but must be constructed of non-corrodible
materials. There are bottling difficulties with the process, however, owing to
foaming. / ,V '/

Ready-to-serve beverages (RTS)

Ahmed (1996) formulated ready-to-serve (RTS) beverages based on ba¬
nana juice which can be stored at room temperature for 9 months. Saxena
etal (1996) reported that the carbonation of RTS blends resulted in sparkling
drinks of excellent sensory quality. The blends containing grape: mango
(3:1) and grape-pineapple (1:1) received the highest sensory quality scores.

Concentration of fruit juices

Concentration by freezing: When water containing a dissolved substance is
progressively cooled pure ice is formed at first and the concentration of the
dissolved substance in the liquid phase increases. By removing the ice at a
suitable stage we can thus obtain a highly concentrated liquid (Khurdia,
1995).
This method was first applied to fruit juices by Gore (1914), who pro¬
duced a concentrate with a richer flavour than that obtained by any other
process because there was no loss of volatile flavours and aromas and the
chemical changes which normally take place during heat concentration did

201
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

not occur. The fruit juice was simply placed in a freezing room in ordinary
ice-cans, surrounded by cold brine, and frozen to a semi-solid cake. This
was crushed and placed in the basket of a sugar centrifuge moving at a
moderate speed. The liquid that passed through the basket was collected;
the ice remained behind and, after being washed free from syrup by a fine
spray of water, it was discarded. This operation was repeated once or twice
until a syrup containing about 50% of dissolved solids was obtained. Much
of the success of the method depends on having the ice crystals large enough
to be held up by the basket of the centrifuge and to permit the free passage j
of the liquid phase. Too rapid freezing, resulting in very small ice crystals, is
unsatisfactory (Morries, 1951).
Concentration in vacuum evaporators: The chief disadvantage in vaccum
evaporator at low temperature (37.78°C) is that it destroys volatile flavours
and aromas completely. Although the vitamin C may be largely retained, |
the product is usually blend and lacks character. Many attempts have been
made to trap the flavours and re-introduce them to the juice after concen¬
tration. Evaporators for fruit juices range from simple glass-lined vacuum
pans to multiple-effect tubular evaporators and evaporators of the climbing
and falling film type with tubes of stainless steel. All parts exposed to the
action of the juice must be of non-corrodible metal (Reavell, 1937).

Candied fruits
Glazed fruit: For this purpose a very highly supersatuated syrup contain¬
ing about 80% or more of sugar is used. The fruit is placed in it while boiling
and allowed to cool until local graining can be intruded by stirring at the
side of the pan. It is then ladled out and arranged on a suitable wire support
to harden and dry. It should not be sticky.
Sauces: Sauces are generally of 2 kinds, i.e. thin and thick. Thin sauces
mainly consist of a vinegar extract of various flavouring materials like spices
and herbs. Their quality depends mostly on the piquancy of the material
used.
Thin sauces: As mentioned above thin sauces mainly consist of a vinegar
extract of various flavouring materials like spices and herbs.
Some sauces are matured by storing them in wooden barrels. This de¬
velops their flavour and aroma. Freshly prepared products of this kind often
taste raw and harsh. For sauces of high quality, the spices, herbs, fruits
and vegetables are macerated in cold vinegar. Sometimes, extracts are pre¬
pared by boiling them in vinegar. The sauce is filtered through a fine corrosive
mesh sieve of non-corrodible metal according to the quality required. The
skins, seeds and stalks of spices should not be allowed to pass through the
sieve, as they spoil the appearance of the sauce. The usual commercial
practice is to prepare vinegar extracts of each kind of spice and fruit separately
either by maceration or by boiling and then to blend them suitably before
putting them into barrels for subsequent maturing (Giridharilal et al, 1986).

202
 FRUITS AND VEGETABLES

Soya sauce: Soya sauce is made from soybean. The sauce has usually a
predominant saltish taste and has a dark brown colour. It is made by cooking
soybean and wheat, and then allowing the mass to undergo mould fermen¬
tation for 3-4 days. The mass is then mixed with strong brine (15-20%) to
form a mass which is placed in wooden barrels to bring about bacteriological
and chemical changes. In due course, a thick brown liquid is formed. It is
then boiled and filtered. To the filtered liquor molasses are added to taste,
before bottling.
The other examples for thin sauces are mushroom ketchup, walnut
ketchup and Worcestershire sauce.
Thick sauces: A sauce which does not flow freely and which has a high
viscosity is called a thick sauce. It should contain at least 3% acetic acid so
that it has good keeping quality. The acidity should not, however, exceed
3-4%, otherwise, the sauce would taste sharp. The sugar content may vary
from 15-30%, according to the kind of sauce made. Usually malt vinegar is
used which besides causing acidity, improves the flavour. The sweetness is
derived partly from fruits like date, raisin, sultanas, apple and tomato and
partly from the sugar. The colour of the sauce varies with the raw material
used. Sometimes a little caramel is used.
Raw materials are generally cut into pieces or slices of the desired size
and cooked till they are soft. Slow cooking at temperatures below the boiling
point, yields better results than brisk treatment at a higher temperatures.
Onion and garlic are added at the start to mellow their strong flavours.
Spices are coarsely powdered before they are added. Sometimes vinegar
extract of spices is used instead. Thickening agents are added to prevent or
retard sedimentation of the solid particles in suspension. In India, apple
pulp is often used for this purpose. Sometimes, the fruit, which is used for
making sauce, is boiled, pulped and used as a filler.
The starches of maize, potato, arrow root (cassava starch), sago and rye
also are used as thickening agents. The use of Indian gum, locust kernel
gum, tragacauth, karaya gum, gelatin, irish moss, pectin and other similar
substances is also advised. These are not, however, as good as the starches.
Preparation of tomato ketchup: Tomato ketchup is made by concentrating
tomato juice or pulp without seeds and pieces of skin. Spices, salt, sugar,
vinegar, onion, garlic etc. are added to the extent that ketchup contains not
less than 12% tomato solids and 28% total solids.
Raw material: Select sound ripe tomato having deep red colour. Remove
all green and yellow portions. Green fruits makes the ketchup inferior in
colour and flavour.
Pulp preparation and juice extraction: Collect the prepared fruit in an
aluminium or stainless steel vessel and crush thoroughly with a wooden
laddie. Cook the crushed mass for 5 min. and mash it well while cooking.
When it is sufficiently soft, strain through fine mosquito net cloth or 1-mm-
mesh stainless steel sieve. Discard the seeds and skins.

203
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Recipe Value

Tomato juice/pulp (Sp.gr. 1.022-1.027) 3.00 kg

Onion (chopped) 37.50 g
Garli£ (chopped) 2.50 g
Clover (whole) headless 1.00 g
Cardamom (coarsely powdered) 120.00 g
Black pepper (coarsely powdered) 120.00 g
Zira (coarsely powdered) 120.00 g
Mace (javatri) not ground 0.25 g
Cinnamon (broken) 1.75 g
Red chilli powder 1.25 g
Salt 31.20 g
Sugar (It can be increased up to about 150 g to get a ketchup 100.00 g
with a slightly sweeter taste)
Vinegar (6% acetic acid) 150.00 ml

To the pulp add about one-third of the sugar given in the recipe. Place
the spices (onion, garlic, clove, cardamom, black pepper, zira, mace, cinna¬
mon, red chilli powder) in a muslin bag and immerse it into the pulp. Heat
the pulp till it thickens and is reduced to one-third of its original volume.
Remove the muslin bag and squeeze it well to extract the aroma and flavour
of the spices. Add vinegar, salt and the remaining sugar. Heat the mass for
a few minutes so that the volume of the finished product is about one-third
of its original pulp.
To a small quantity of finished product, add the preservative sodium
benzoate @ 295 mg/kg finished product and mix thoroughly. Transfer the
dissolved preservative to the rest of the product and mix thoroughly. Pour
the finished product into medium-size sterilized bottles, seal them air-tight
with a cransed seal and pasturize in boiling water for 30 min. Cool the
bottles in air and store in a cool dry place.
Important points to be followed are:
1. Chilli powder, spices, onion, ginger and garlic should be tied loosely
in a muslin cloth bag.
2. Acetic acid and colour may be added towards the end of boiling.
3. One-third of the sugar may be added in the begining to preserve the
red colour of the pulp.
4. Instead of clove, cinnamon and cardamom, essence of these spices
may be added more conveniently.
5. Garlic may or may not be added, depending on consumer’s accept¬
ance.
6. Acid Magenta II colour is avoided. Choose dot red colours or orange
colours such as eiythrosine, carmoisine, sunset yellow etc.

Pickling
The preservation of fruits and vegetables in common salt or in vinegar is
called pickling. Spices and edible oils may be added to the product. Raw

204
 FRUITS AND VEGETABLES

mango, lime, turnip, cabbage, cauliflower, etc. are preserved in the form of
pickles, which have become popular in several countries. Pickling is done (z)
by curing and fermentation with dry salting or fermentation in brine, or
salting without fermentation and (zz) by finishing, and packing (Giridharilal
et al, 1986). In dry salting, for every 100 kg prepared vegetables, 3 kg salt is
used in alternate layers in the keg or barrel. After three-fourths filling, the
mass is covered with wooden board under some weight. Brine is formed in
about 24 hr. Fermentation is usually completed in 8 to 10 days at 27-32°C,
but it may take 2-4 weeks in cold weather. Vegetables such as cucumber,
which do not contain sufficient juice to form brine with dry salt are fer¬
mented in brine (Girdharilal etal, 1986).
Lactic acid fermentation: The addition of salt permits the naturally present
lactic acid bacteria naturally present to grow, thereby rapidly producing
sufficient acid to supplement the action of salt (Desrosier, 1970). In this
process, the fermentable carbohydrate reserve is converted into acid, whose
level in cucumber ranges from 0.8-1.5% expressed as lactic acid. In the
commercial production of fermented salted cucumbers, the salt concentra¬
tion is maintained at 8-10% during the first week, and thereafter until 16%
salt concentration is obtained in solution. The fermentation is completed
within 4 to 6 weeks, as evident from the change in the tissue characteris¬
tics. The salt stock is freshened twice in warm water (43-45°C) for 10-14 hr.
The freshened salt stock is packed in consumer units with weak vinegar
(2.5% acidity) to prepare sour pickle. Sweet, spiced vinegar is used for sweet
pickle. Spices are added to the acidified brine.
Sauerkraut is another lactic acid-fermented product made from cab¬
bage. The shredded cabbage is mixed with salt and on an average 1.5-2.0%
lactic acid is produced, as fermentation may be complete in a little over a
week. About one-half as much acid is produced, as there is sugar present in
the cabbage. In India, oil pickles are highly popular.
Cauliflower, lime, mango, turnip, bamboo, jack fruit, kair, karortda etc.
are used to make oil pickles. Raw material (whole and cut into desired pieces)
is washed, then mixed with spices such as chilli powder, turmeric powder,
cumin, cardamon, cinnamon, clove, black pepper, fenugreek, nigella, gin¬
ger, onion, mustard seed, methi etc. Mustard or gingelly oil is generally
used.
The main problem in pickles is the spoilage by either yeasts or moulds,
since both can grow in the presence of acid. Thus, an anaerobic environ¬
ment can control these microorganisms, which can be provided by putting
extra layer of oil over the fruits and vegetables in oil pickle and brine or
vinegar layer in pickles packed with brine or vinegar. Under properly con¬
trolled conditions, the salted fermented cucumber may be held for several
years, as the salt protects the fruit pickles against microbial spoilage (Kanekar
etal, 1989).

205
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

STORAGE OF FRUITS AND VEGETABLES

VEGETABLES
i

The quality of fresh vegetables is retained when moisture loss is prevented j

and enzyme activity is kept at a minimum. The loss of moisture causes!
vegetables to wilt and become limp. Fresh green vegetables such as salad j
greens and celery retain crispness and firmness when kept in a covered
container or plastic bag in refrigerator. Storage conditions suited to the
quantity of greens permit only a minimum loss of water from the cells, as
the equilibrium becomes established between the moisture in the greens ;
and the moisture held in the air surrounding the greens. When the greens
are washed before storage, they must be well drained to avoid decay.
The degree of maturity in the harvested vegetables influences their colour,
texture, flavour and nutritional value. The sugar content of young, tender
corn and pea decreases progressively with the increase in temperature.
However, prompt cooling and refrigeration decreases the loss of sweetness.
In the vegetables rich in strach such as potato, an increase in sugar
content and decrease in starch occur when stored in the refrigerator. Potato
stored at 16°C retains its starch content. Mature onions keep well in a dry,
airy place. Winter squash, tubers and root vegetables should be kept in a
cool place.
Enzymes contained in plant tissues continue to promote metabolic ac¬
tivity after harvest and are responsible for many changes that occur during
storage. Cold or near-freezing temperature retards enzyme activity and thus
reduces deterioration in plant tissues. Vegetables also retain vitamins more
effectively at refrigerator than at room temperature. Frozen vegetables are
stored in frozen food compartment at -18°C. Canned vegetables are kept in
a dry place to avoid rusting of cans. Dried vegetables are stored at room
temperature in a dry place.

FRUITS

Controlled low temperature and humidity used commercially provide the

best storage conditions for fresh fruits because they retard natural respira¬
tion and microbial spoilage. The controlled atmosphere technique regulates
the levels of oxygen and carbondioxide surrounding the fruit and thus de¬
lays ripening and extends the availability of several fruits. Ideal storage
conditions are impossible to achieve at home, and quality is maintained
best at refrigerator temperature although moisture loss does occur.
Under-ripe fruit may be ripened at room temperature and then stored
in the refrigerator. Apples can be stored for an extended period at cold tem¬
peratures, but most other fruits should be used within a relatively short
time. Berries cannot be stored for prolonged periods commercially or at

206
 FRUITS AND VEGETABLES

home. Grapes and berries are stored with stems and caps intact. Fresh
fruits should be stored in compartments, away from other food, because
they absorb and emit odours. They may be placed in plastic bags to reduce
moisture loss and stored on refrigerator shelves.
Dried fruits may be stored in covered containers at room temperature.
When the climate is humid, it may be necessary to store dried fruits in the
refrigerator to retard moisture absorption and mould growth. Frozen fruits
are stored at (—18°C) and thawed partially for serving. Fruits thawed in the
refrigerator usually have a more pleasing texture than those thawed at room
temperature (Eva Medwed, 1986).
The modern methods of food preservation in general and of fruit and
vegetable preservation in particular may be broadly classified as follows
(Giridharilal etal, 1986):

Physical methods of preservation

By removal of heat (preservation by cold) Refrigeration, freezing preservation, dehydro freez¬
ing preservation, carbonation

By addition of heat (thermal processing) Stationary pasteurization, agitating pasteurization or

sterilization, flash pasteurization or HTST process¬
ing etc.

By removal of water (evaporation or Sun-drying, dehydration, low temperature evapora¬

dehydration) tion or concentration, freeze-drying, Accelerated
freeze-drying, foam-mat drying, puff drying etc.

By irradiation Dosing with uv or ionizing radiation etc.

Chemical methods of preservation

By addition of acid such as vinegar or Pickled vegetables, fish, and meat
lactic acid

By salting or brining Vegetable or fruit pickles, salted fish, etc., salt-cured

meat and pork etc.

By addition of sugar and heating Fruit preserves, jams, jellies, marmalades etc.

By addition of chemical preservatives Using water-soluble salts of sulphur-dioxide benzoic

acid, sorbic acid and a few like hydrogen peroxide,
etc. which are permitted as harmless in foods.
By means of substances of bacterial origin such as
tylosin, resin, etc. which are permitted to a limited
extent, in some cases as harmless additives.

By fermentation Alcoholic and acetous fermentation as in the case

of fruit wines, apple cider, fruit, vinegar etc.

FRUIT AND VEGETABLE JUICES AND DRINKS

There has been a considerable increase in the consumption of fruit and

vegetable juices in the world during the last few years and there are possi-

207
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

bilities of its further increase. The beverage industry is by far the largest
outlet for fruit juice and concentrates absorbing more than 80% of produc¬
tion. In India a little more than 60% of the fruit produced is used in fruit-
based beverages. Many different types of beverages, such as fruit juices,
fruit drinks, squashes, cordials and fruit punches, are available. They are
broadly defined as:
Fruit juice: This is a natural juice pressed out of a fruit, and is unaltered
in its composition during preparation and preservation.
Fruit drink: This is made by liquifying the whole fruit and at least 10% of
the volume of undiluted drink must be whole fruit. It may be diluted before
being served.
Fruit squash: This consists essentially of strained juice containing mod¬
erate quantities of fruit pulp to which sugar is added for sweetening eg.,
orange squash, lemon squash, mango squash, etc.
Fruit cordial: This is fruit squash from which all suspended material is
completely eliminated and is perfectly clear, e.g. lime juice cordial.
Fruit punches: These are made by mixing the desired fruit juices at the
time when it is served.
Fruit juice concentrate: This is fruit juice which has been concentrated by
the removal of water either by heat or by freezing.
Sherbats: This is cooling drink of sweetened diluted fruit juice.

FRUIT JUICES

Fruit juices are valuable from the nutritional point of view. They are rich in
minerals, vitamins and other nutritive factors. Besides, fruit juices are deli¬
cious and have universal appeal. In developed countries fruit juices com¬
monly form part of the breakfast and are produced in very large quantities.
(In the USA, the annual production of juices is more than 500 million kilo¬
litres). Fruit juices do not form the normal diet in our country and the fruit
juice industry is in its infancy in India. Preparation of the juice is limited
mostly to home-scale production. The fruits generally used for making juice
are orange, grape, apple, pomegranate, melon, mango, etc. Of late, the manu¬
facture of squashes on a commercial scale has made some progress
(Shakuntala and Shadaksharaswamy, 1987).
Fruit juices are best in taste, aroma and colour, when freshly expressed.
The most important problem, therefore in the fruit juice industry is to use
such methods as would help retain these properties to the maximum ex¬
tent. The steps involved in the processing of juice are selection of fruit,
extraction of juice, deaeration, straining and preservation.
Freshly picked, sound and suitable varieties of fruits are selected and
thoroughly washed. The juice is extracted by crushing and pressing the
fruits; while extracting the fruit juice, fruit components other than sacs or

208
 FRUITS AND VEGETABLES

cells in which juice is present are to be avoided as far as possible. Further,

the juice should not be unduly exposed to air. The juice (particularly pure
orange juice, which is susceptible to the action of air) is immediately deaerated
by subjecting it to a high vacuum. After deaeration, the vacuum is released
with nitrogen gas, the juice is transferred into containers which are
hermitically sealed and frozen. Fruit juices in sealed containers keep well
for about 2 years in the frozen condition. In the alternative, the fruit juice is
spray dried.
When clear juice is required, the juice is strained and complete removal
of all suspension is effected by filtration and clarification. Clarification needs
the removal of colloidal suspensions of the fruit juice. This can be brought
about by freezing, heating, use of enzymes of finning agents. The finning
agents produce a voluminous flocculant precipitate which gradually settles,
carrying down with it colloidal suspensions. The clarified juice, as in the
case of whole fruit juice, is preserved by freezing, pasteurization or the ad¬
dition of chemical preservatives, such as sodium benzoate or bisulphite.
The fresh juices extracted from the various fruits contain mainly sugars
and small quantities of vitamins and minerals. The acid taste is due to the
presence of organic acids. Fruit juices of various sorts have been prepared
for the food-specialty trade for many years, but recent years have seen great
advances both in the numbers of these refreshing beverages and their at¬
tractiveness and quality. Lime juice from the tropical islands has long been
sold by dealers in high-grade food specialities, whereas grape juice, both
red and white, followed thereafter. A great impetus has taken place in the
production and marketing of citrus-fruit juices including those from or¬
anges, lemons, and grape fruit. Some of these are also called fruit cocktails,
especially if mixed with other ingredients.
The popularity of these types of product is doubtless largely due to their
detectable flavours, and perhaps, in part also, to the emphasis which has
been given to vitamins in the past decade, as many fruits contain vitamin C.
To secure good quality the fruits used are picked at a definite, carefully
regulated time as each fruit has a particular period when the acid and sugar
contents are at optimum. Oranges for example, should be matured when
picked, otherwise, the juice is bitter, whereas grapes may be used for juice
when slightly under-ripe. The fruit used for juices must be absolutely sound
and clean. Rot, mouldiness, fermentation or dirt in crushed fruit spell fail¬
ure in so far as a high quality beverage is concerned.Each fruit present an
individual problem in regard to harvesting, crushing, pressing, clarifying
and preserving. In crushing, for instance, the metal of the crusher should
be of such a nature that it is not attacked by the fruit acid, thus imparting
colour and changing flavour. Certain fruits darken or lose their attractive
appearance on exposure to air even for short periods of time. All fruit juices
are subjected to spoilage by microorganisms unless properly handled and
stored.

209
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Use of fining agents

This method aims at producing a voluminous flocculent precipitate which
settles gradually. Carrying down with it divided particles and colloid sus¬
pension that are responsible for cloudiness in clarified juices. A number of
substances like gelatin,mixture of tannin and gelatin, milk, white of eggs,
casein etc. have been used by wine makers and brewers for clarification.
The tannin gelatin method is most widely employed for clarifying fruit juices.
Finings are of 3 kinds:
(z) Enzymes which destroy the colloids present in the juice. Various kinds
of enzymes such as proteolytic, pectin- decomposing, hydrolytic, starch-
liquifying enzymes etc. are some times used to remove pectin, proteins, and
starch from fruit juices. The bulk of suspended matter especially in the case
of apple juice, consists of proteins and pectin like substances; gelatin, ca¬
sein and albumen are normaly used to clarify the fruit juices.
(ii) Finings which are purely physical in their action, e.g. infusorial earths.
Generally infusorial earths such as Spanish clay, kaolin, bentonite etc., which
are known as titter-cells are employed for the clarification of fruit juices.
Usually 0.5-0.6% of the earth is mixed with the juice and the mixture then
passed through the filter press.
(zzz) Chemical finings which act on gummy and colloidal substances
present in juice to form insoluble coagulates that settle down easily, e.g.
gelatin, albumen and casein.
Clarification by freezing: Colloidal suspensions when subjected to freez¬
ing, are readily precipitated on thawing. Apple juice particularly responds
very well to this treatment.The bulk of fruit juice is subjected to refrigera¬
tion for several months to complete the precipitation. The clear juice is then
bottled.
Clarification by heating: It is a well known fact that colloidal material in
fruit juices usually coagulates, when the juice is heated, and settles down
readily. To get good results, the juice is heated to about 82°C for 1 min. or
less and then cooled down rapidly, the great advantage of this method is
that it also removes from the juice those substances which would otherwise
be precipitated during pasteurization of the juice. Clarification of pome¬
granate juice is a typical example of this process.

Types of fruit juices

Cider: Freshly pressed apple juice or sweet cider is a beverage held in
high esteem in many parts of this country, particularly in the Northern and
Atlantic states where the apple has been the most characteristic nature
fruit for generations. With the recent creation of markets for bottled cider
which may be held for a considerable period before use, refinements in the
clarification of the juice have been developed. One of the methods suggested
for this purpose has been the combined utilization of gelatin and tannin for
precipitation of suspended colloidal material, followed by filteration. En-

210
 FRUITS AND VEGETABLES

zyme preparations, capable of attacking pectins and starches which are

likely to cause a haze in juice, have also been found useful in this respects.
Grape juice: Grape juice has been a popular beverage for many years. In
usual procedure grapes are first carefully washed or subjected to a water
spray, then crushed and stemmed mechanically. Ordinary Alteration will
not readily remove completely the turbidity of grape juice, but this may be
accomplished by adding organic materials such as casein, or through the
use of enzyme concentrates derived from moulds. Either of these treatments,
followed by filtration, will produce a relatively clear product. The clarified
juice is again heat treated at a temperature of 76.3°C or more for 30 min.
and filled into the final container which should be sterile.
Orange juice: Fresh orange juice is one of the most popular fruit bever¬
ages, and much efforts have been made on producing high-grade commer¬
cial products of this nature. To have satisfactory flavour, it is necessary that
total acidity of orange juice should be at least 1%. Freezing has also been
used as a means of preserving citrus juices. Juice sealed in vaccum and
stored in airtight containers at -17.8°C is said to keep well.
Grape-fruit juice: The juice of grape fruit has been canned successfully for
a number of years and has obtained considerable popularity. The canning
of grape fruit juice consists of extracting and straining the juice, adding the
sweetening, processing and cooling.
Lemon juice: The canned juice of lemon is also a common product at
present. This fruit is also subjected to flavour and colour changes which
require the removal of air as far as possible. Lemon juice may also be dried
to a powder form using spray-drying equipment.
Tomato juice: Another relatively recent product which has acquired high
popularity not merely for its acceptable taste but also because of its vitamin
value.
Plant ripened and fully red tomatoes should be used. All green, blem¬
ished and over-ripe fruits should be rejected as they adversely affect the
quality of the product. Juice from over-ripe tomatoes is usually thin and not
quite pleasant in its taste and aroma. The yield, colour and flavour of the
juice depend on the degree of ripeness of the tomatoes, the variety and the
place where grown.
1. The juice should be deep red. As the red colour is contained in the
fibres and not in the serum of the juice, the fibrous portion as much
as possible should be incorporated in the juice in finely divided condition.
2. The juice should posses characteristic taste and flavour of tomato.
3. Acidity of the juice as citric acid should be about 0.4%.
4. For uniformity in quality, either the tomatoes used should be from
one stock and place or the juice should be suitably blended.
Washing and trimming: For thorough cleaning, tomatoes should be washed
in plenty of running water. For commercial production, rotary washes or
through washers fitted with moving conveyor belt and soft roller brushes
are used.
211
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Crushing: After trimming tomatoes are cut into 4 to 6 pieces for boiling to
soften the tissues.
Pulping: Tomatoes can be pulped by the hot process or by the cold process.
Hot pulping: The crushed tomatoes are boiled in their own juice in steam
jacketed stainless steel pans or in aluminium pans for 3 to 5 min. to facilitate
pulping.
Advantages: 1. The tendency of the juice to separate into liquid and pulp
can be overcome if the pectin naturally present in the seed and in the skin
can be incorporated into the juice. During the preliminary boiling, this pec¬
tin is released and it thickens the pulp.
2. Boiling sterilizes the juice partly, thereby checking to some extent
the growth of microorganisms which cause fermentation etc., in the juice. It
also inactivates the oxidative enzymes which are responsible for the de¬
struction of vitamin C.
3. A light cooking releases red colour pigment in skin.
4. Yield of juice is higher.
Cold pulping: The tomatoes are crushed in the cold and as such passed
through a pulper.
Defects: 1. As compared to the hot process, the extraction of juice is
some what difficult and the yield is less.
2. Air gets incorporated into the juice in the process of extraction and
this oxidizes vitamin C in the juice.
3. Colour of this extraction is low.
4. Microbial spoilage is more
Total solid content of 5.66% at 20°C
Common salt and sugar: 4 to 6 kg common salt is added/1,000 kg juice;
sometimes sugar is also added to improve taste.
Packing
Juice can be packed in glass bottle or cans.The juice is homogenized,
heated to about 82.2°C-87.8°C, poured into hot sterilized cans, without
leaving any head space.The cans are double seamed, sterilized at 100°C for
30 min. and cooled in running water.
Tomato cocktail
Tomato cocktail is gaining popularity in many five star hotels and res¬
taurants. It is prepared just before serving and sometimes is also served
from stock. Although the recipes vary, the main constituent is tomato juice
with common salt, vinegar, worcestreshire sauce, lemon juice. Tabasco sauces
are added in different proportions to suit the palate. Simmer the tomato
juice, with the spices loosely tied in a cloth bag for about 20 min. in a
covered vessel. Then add the lime juice, vinegar and common salt. Other
fermented juice products are fermented cider (fermented apple juice), apple
wine, apple brandy, beer, whisky and scotch.

212
 FRUITS AND VEGETABLES

SQUASHES

The term squash refers to a fruit juice added in the concentrated sugar
syrup and preserved.
Essentials of squash
1. Fruit—Usually, citrus juicy fruits such as lemon, orange, plums,
pineapple, grapes, mango, kokum are used.
2. Sugar—It acts as preservative and gives sweet taste.
3. Acid—It acts as preservative and gives sour taste.
4. Chemical preservatives—Potassium metabisulphite or sodium
benzoate.
Steps in squash making
1. Selection of fruit—select fresh, juicy, fully ripe, firm wholesome and
fresh fruit.
2. To soften the fruits, keep them in fresh lukewarm water for 10 min.
3. Extract the juice and strain it.
4. The amount of sugar, water and preservative depends on type of fruit.
For example, lemon juice 30.0%, water 15.0%, sugar 55.0%; and mango juice
45.0% water 10.0% and sugar 45.0%. In 450 ml of squash, 225 mg potassium
metabisulphite is required.
5. Prepare syrup with sugar, citric acid and water and cool it.
6. Add strained fruit juice in the cooled prepared syrup.
7. Add preservative dissolved in small quantity of cooled squash.
8. Add permitted colour and essence in adequate amounts.
9. Pour in dry sterilized bottle through a funnel leaving 2.5 cm
headspace.
10. Close the bottle and seal it.
Squashes are prepared by the addition of sugar, organic acids and pre¬
servatives to freshly expressed fruit juices. Squashes are usually diluted
with water before consumption.

Lime and lemon squash

Take fresh, fully ripe, sound fruits and wash them thoroughly in fresh
water, cut them into halves with a stainless steel knife. Express juice from
limes in a lime-juice squeezer or in small basket press; for lemon use cone-
type extractor, strain the juice through mosquito net cloth to remove seeds
and coarse pulp. Add suitable quantity of edible yellow colour (permissible
brand) to bring out desired shade in the finished product (juice 1.0 kg,
sugar 1.8 kg and water 1.2 kg).

Orange squash
Select fresh, fully ripe, sound fruits, and wash them thoroughly with
fresh water. Remove peal of loose-skinned orange, separate the segments
and extract the juice in a screw press.Strain the juice through a coarse
muslin, or mosquito net cloth. Cut the tight-skinned oranges into halves

213
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

and express the juice in a cone-type extractor. Mix thoroughly ingredients

(juice, 1 kg sugar 1.7 kg water 1.3 kg, citric acid 30-35 g, orange essence 1 Vz
teaspoon) till the sugar and citric acid are dissolved. Slightly warm if neces¬
sary and strain the mixture through cheese muslin cloth. Add potassium
metabisulphite @619 pg/kg finished product. Dissolve this powder in small
quantity of water and mix it thoroughly in the product. Bottled and store,
when required, for 1 cup add 3 cups of water.

Cashew apple squash

Extract the juice and clarify using gelatin solution, add 60 g lime juice,
12 g citric acid and 670 g sugar for every kg of clarified cashew apple juice.
Mix well till the sugar is dissolved. Add potassium metabisulphite @610 pg
or sodium benzoate @ 700 mg/kg finished product respectively. Fill the
squash into clean bottles, cork tightly and store in cool place. As and when
required, for every cup of the squash, add 3 cups of chilled water. Mix and
use as a fresh drink.

Jack fruit squash

Cut the ripe fruit into 8 or 16 pieces first across and then length wise.
Remove the gunny core by means of a sharp knife from the bulbs. Smear a
little cooking oil on the hand to prevent stickiness and to seperate the bulbs
from the rind and the surrounding carpels.Trim off the top and bottom of
the bulbs, remove seeds and their thin covering. Cut the bulbs into halves,
quarters or slices and soften by heating them slowly in about half their
weight of water and stirring with a wooden ladle and mash into a fine pulp
and mix with sugar syrup (Pulp 1 kg, sugar 1.7 kg, water 1.3 kg and citric
acid 40 g). Jack fruit squash is a palatable beverage with pleasant taste and
aroma and keeps volumes well. Before use, dilute it with 3 volumes of water.

Sapota squash
Pass the fruit segment through a meat mincer and obtain a uniform
pulp. Wrap the pulp in thick cloth and press out the juice with gloved hands
or a small basket press. Mix the ingredients (pulp 1 kg, sugar 1.2 kg, water
1.0 kg and citric acid 40 g) and heat the mixture thoroughly into a uniform
syrup mass, strain it through coarase muslin cloth.

FRUIT JUICE CORDIALS

Fruit juice cordials differ from the fruit juice squashes in that the suspended
fruit pulp has been removed.They are usually dilute with water before con¬
sumption.

Lime juice cordial (CFTRI, 1990)

Extract the juice from lime as in squash and store in glass containers.

214
 FRUITS AND VEGETABLES

Winchester bottles or carboys after adding potassium metabisulphite @1.5

g/kg juice. Allow the juice to settle for about a month. Decant the clear juice
without distrubing the sediment and strain it through fine muslin cloth.
Mix the ingredients (juice 1 kg, sugar 1.25 kg and water 1 kg) thoroughly
with slight warming. If necessary, strain the product through fine muslin
cloth. Add potassium metabisulphite (preservative) @150 mg/ kg finished
product. Bottle and store.

CARBONATED BEVERAGES

The production and use of carbonated beverages have increased greatly in

recent years. The business has extended from a relatively small, highly sea¬
sonal hot-weather industry to one of the large proportions. There are over
5,000 establishments in the USA producing carbonated products with an
annual value of more than 200 million dollars.Some of these products are
carbonated natural - fruit beverage such as grape juice and cider. The great
bulk, however, is composed of beverages, of which ginger ale is perhaps the
outstanding example, containing as a base a flavoured syrup which may
also be fortified with some fruit acid. Although the food value of these prod¬
ucts is not high, they serve a useful function especially in warm weather.
Ginger ale is the carbonated beverage prepared from ginger ale concen¬
trate, flavour, harmless organic acid, potable water, and a syrup of one or
more of the following sugars, i.e. invert sugar, dextrose with or without the
addition of caramel colour.
It also contains aromatic and pungent ingredients, citrus oils and fruit
juices.
Ginger ale is one of the most popular beverages and is produced in 2
common forms, the so-called golden ginger ale and pale dry ginger ale. The
former usually has a sugar concentration between 8.5 and 9.5 while the
sugar content of the latter is slightly lower, (8-9%). The pale dry is generally
more acid than the golden.
Other carbonated products some times have flavours made from fla¬
vouring oils and occasionally from synthetic organic derivatives. Sassafras
flavour, for instance, is prepared from oil of sassafras and methylsalicylate,
oil of wintergreen.
Most carbonated beverages of the ginger-ale type are not heat-treated
and, therefore, would seem to present the possibilities of spoilage of micro¬
organisms. Fortunately, however, carbondioxide itself when present under
pressure tends to inhibit the growth of many types of microbes which would
otherwise cause spoilage.
The water used requires special consideration from a chemical stand
point also, as the lower the total solids content the better the product. It is
undesirable to employ water having more than 15 grains of total solids per

215
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

gallon, and the presence of calcium sulphate (hard water) should be avoided.
Distilled water is suitable for use but is not commonly necessary. It is some¬
times necessary to have the water supply chemically treated to make it
satisfactory for beverage purposes, because the ability of water to take up
carbondioxide gas properly is of great importance. The necessity of having
an odourless and tasteless water supply is equally essential and the final
treated water must be clear as crystal.
Another main ingredient of carbonated beverages is syrup. Although
present in relatively small quantity in comparison with water, it is the syrup
which supplies the flavour and whatever food value the product presents.
There are a great variety of syrups, all of which contain sugar and some
flavouring material, which may be from natural fruit or more often syn¬
thetic flavours.
Fruit acids such as citric acid are commonly used as an important con¬
stituent of syrups and tend to accentuate the other flavouring ingredients
used. The sugar used in these syrups is largely sucrose, although it is now
legally possible to use corn sugar without declaration on the lable. The sugar
content of concentrated syrup is usually high enough to restrain growth
and to prevent spoilage, even though stored some time before use, but mi¬
crobes gain entrance if they are not killed by the sugar. Therefore it is es¬
sential that the strictest sanitary precaution be taken in making syrups and
keeping them chemically and biologically clean during storage. The third
ingredient is the carbondioxide gas. This is usually purchased in cylinder
containing it under high pressure, which facilitates later operations as the
pressure is necessary. To increase the solubility of carbondioxide in water,
the water in beverage plants is usually cooled close to the freezing point
before the start of bottling operations. This chilled water is sometimes car¬
bonated previous to the actual filling operations.
The 3 chief ingredients, syrup, water, and carbondioxide are ultimately
combined in the bottle in definite proportions and in such a manner that
the carbondioxide in the product has a pressure of 3 or 4 atmospheres. The
filling operations are carried out in highly automatic machines which cap
the bottle after they are filled. The bottles are usually conveyed through a
testing tank filled with water which checks the capping operations, as leaks
may be detected by bubbles of carbondioxide rising to surface.
The bottles used for this industry are generally returnable and thus
may be used several times. Therefore another important operation in a bev¬
erage plant is the thorough cleaning of all bottles used for the product.
Often this equipment is the most expensive apparatus in the plant.
Yeasts and related organisms are the principal causes of spoilage in
carbonated beverages, as the acidity and sugar content are favourable to
their development, although other micro-organisms—bacteria or moulds
sometimes cause trouble. Most bacteria are inhibited by the acidity of bev¬
erages of this sort, while moulds are unable to grow when high concentra-

216
 FRUITS AND VEGETABLES

tions ol carbondioxide make up the dissolved gas, and exclude oxygen from
the air. Yeasts may cause changes in flavour and produce turbidity and
sediment owing to their growth. When such cloudiness occurs and even the
actual breakdown of the beverages may take place in an infected product,
but careful attention to sanitary procedure throughout the whole train of
operations involved minimizes such infection and spoilage. Storage of such
bottled products should be at low temperatures and in the absence of sun¬
light. Carbonated beverages containing certain types of flavouring oils are
likely to deteriorate in flavour if exposed to direct sunlight.

REFERENCES

Ahmed, J. 1996. Studies on juice extraction quality of some varieties of banana for the prepa¬
ration of banana basal beverages. Indian Food Packer 50(4): 5-7.
CFTRI, Mysore. 1990. Home Scale Processing and Preservation of Fruits and
Vegetables, pp.65-70. Central Food and Technology Research Institute, Mysore, India.
Charman, S. 1971. Fundamentals of Food Engineering, edn 2. AVI Publishing Co., West Port,
Connecticut.
Cruess, W.V. and Irish, J.H. 1940. Fruit beverage investigations. California Agricultural Ex¬
periment Station Bulletin 359: 526-68.
Desrosier, N.W. 1970. The Technology of Food Preservation. The AVI Publishing Co. Inc., West
Port, Connecticut.
Eva Medwed. 1986. Food Preparation and Theory, pp. 166, 188 Prentice-Hall Inc., New Jersey
Forrest, J.C. 1968. Drying processes, (in) Biochemical and Biological Engineering Science.
Blakebrough N. (Ed.). Academic Press, New York.
Girdharilal, Siddappa, G.S. and Tandon, G.K. 1986. Preservation of Fruits and Vegetables.
Indian Council of Agricultural Research, New Delhi.
Gore, H.C. 1914. Apple syrup and concentrate cider, Year Book No.639. United States Depart¬
ment of Agriculture, Washington DC.
Hall, E.G. 1975. Food Technology in Australia 27: 486.
Kanekar, P., Sarnaik, S., Joshi, N., Pradhan, L., Godbole, S.H. 1989. Role of salt, oil and
native acidity in the preservation of mango pickle against microbial spoilage. Journal of
Food Science and Technology 26: 1-3.
Khurdia, D.S. 1989. Drying and dehydration of fruits and vegetables. Efficient solar drying
system. Trainers Training Course on Low Cost Preservation of Fruits and Vegetables, held
during 4-16 September, at Division of Fruits and Horticultural Technology, Indian Agri¬
cultural Research Institute, New Delhi.
Khurdiya, D.S. 1995. Non-thermal methods as preservation of fruits and vegetables—A criti¬
cal appraisal. Journal of Food Science and Technology 326: 441-452.
Khurdia, D.S. and Roy, S.K. 1986. Solar drying of fruits and vegetables. Indian Food Packer
446: 55-60.
Krishna Kumari, K. 1990. Processing of Soyabean: Technological implications. Proceedings of
Summer Institute on Appropriate Food Processing Technologies for Rural Development, held
at Hyderabad, Andhra Pradesh.
Morries, T.N. 1951. Principles of Fruit Preservation, pp. 67-72. Chapman & Hall Ltd, London.
Olsen, R.K. 1996. A promising market for fruit juices- Central and Eastern Europe. Indian
Food Packer 50(1): 29-34.
Pawar, V.N., Singh, N.I., Dev, D.K., Kulkarni, D.N. and Ingle, V.M. 1988. Solar drying of white
onion flakes. Indian Food Packer 42(1): 15-28.
Reavell, J.A. 1937. Recent work on the concentration of Fruit Juices and Fruit Drying. Chem¬
istry and Industry 56: 618.
Salunkhe, D.K., Do, J.Y. and Bolin, H.R. 1976. Developments in technology and nutritive
value of dehydrated fruits, vegetables and their products, (in) Storage, Processing and

217
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Nutritional Quality of Fruits and Vegetables, pp. 39-78. Salunkhe, D.K. (ed.). C.R.C.
Press Inc., Ohio.
Saxena, A.K., Trotie, M.S. and Berry, S.K. 1996. Studies on the development of grape-mango
and grape-pineapple beverage blends. Indian Food Packer 50(4): 26-28.
Shakunthala, M. and Shadaksharaswamy, M. 1987. Foods, Facts and Principles. Wiley East¬
ern Limited, New Delhi.
Singhal Vikas,1999. Indian Agriculture, pp. 133-42. Indian Economic Data Research Centre,
New Delhi.Somogyi, L.P. and Luh, B.S. 1975. Dehydration of fruits, (in) Commercial Fruit
Processing, pp. 374-421. Woodroof J.G., Luh, B.S. (eds). The AVI Publishing Co. Inc.,
West Port, Connecticut.
Sumati, R. M. and Shalini Rao. 1993. Food Science, pp. 173-5. Wiley Eastern Ltd, New Delhi.
Szulmayer, W. 1971a. From sundrying to solar dehydration. I. Methods and equipment. Food
Technology, Australia 239: 440-441, 443.
Szulmayer, W. 1971b. From sundrying to solar dehydration. II. Solar drying in Australia.
Food Technology, Australia 239: 474-495.
Tressler, D.K. and Joslyn, M.A. 1971. Fruits and Vegetable Juice Processing Technology, edn.
2. AVI Publishing Co., West Port, Connecticut.
Trenssler, D.K., Jeslyn, M.A. and Marsh, G.L. 1939. Fruit and Vegetable Juices. AVI Publication
Co., New York. (This work contains a comprehensive bibliography).
Uma Reddy, M. and Jayashree, K. 1990. Technology relevant to rice based products. Proceedings
of Summer Institute on Appropriate Food Processing Technologies for Rural Development,
held at Hyderabad.
Van Arsdel, W.B., Copley, M.J. and Morgan, A.I. 1973. Food Dehydration. 2 edn, vols 1, 2. AVI
Publishing Co., West Port, Connecticut.
Vimala, V., Kanwaljit Kaur and Hymavathi, T.V. 1990. Processing of millets scope for diversi¬
fication. Proceedings of Summer Institute on Appropriate Food Processing Technologies for
Rural Development, held at Hyderabad.
Woodroof, J.G. and Luh, B.S. 1975. Commercial Vegetable Processing. The AVI Publishing Co.
Inc., West Port, Connecticut.

LEARNER’S EXERCISE

1. Describe similarities and differences in chemical structure and properties among pectin,
pectic acid and protopectin.
2. What are water soluble cell sap pigments? Give their chemical structure and chemical
changes in food preparation.
3. Explain in detail different types of browning occurring in different vegetables and differ¬
ent measures to check browning.
4. Enumerate the preventive methods of browning reaction in fruits and vegetables.
5. Write short notes on best methods of cooking vegetables.
6. Write the importance of green leafy vegetables in our diets.
7. Write in detail about the effect of acid, alkali, metals and heat processing on the plant
pigments.
8. Explain the process of dehydrating vegetables step by step.
9. What are the changes observed during ripening of fruits and how to control ripening.
10. What is dehydration? Differentiate between sundiying and mechanical drying of food
stating merits of each. Give four examples of dehydrated products.
11. Mention the steps involved in the dehydration of grapes.
12. Why and how does the browning of the cut fruits occur? How does addition of lime juice
prevent discoloration of fruits and vegetables?
13. Enumerate the care to be observed during preparation and cooking of vegetables.
14. What are the ingredients that preserve pickles?
15. Explain the steps involved in canning of pineapple.

218
 Beverages ■

B everages used extensively in different countries include coffee, tea,cocoa,

non-alcoholic beverages, alcoholic beverages and beverages based on
fruit juices.

COFFEE, TEA AND COCOA

Many liquids such as coffee, tea, cocoa, soft drinks and alcohol-containing
drinks are considered as beverages. These contain stimulants or flavouring
agents which perform some useful functions but are not essential for the
proper functioning of the body. Soft drinks are non-alcoholic beverages con¬
taining syrup, essences or fruit concentrates that are mixed with water or
carbonated water. The basis of all alcoholic drinks is ethyl alcohol or simply
alcohol.

COFFEE (COFFEA SPP.)

Coffee is an evergreen shrub or small tree indigenous to central Africa and

Asia. There are many species of coffee, but 3 species are of commercial
importance viz. Coffea arabica, which supplies the largest and the best quality
of coffee beans, Coffea robusta, (C.canephora) which yields beans of lower
quality, and Coffea liberica, whose beans are of still lower quality. Coffea
arabica is indigenous to Ethiopia and was introduced to India through Ara¬
bia. It is cultivated in South India, mainly in Karnataka, Kerala and Tamil
Nadu. It is best grown in the American tropics, where Brazil is by far the
largest producer and exporter of Arabica coffee.
Considerable quantities of C.robusta are also produced in India because
the plant can be cultivated at a lower elevation, is longer living and disease
resistant, and the yield of coffee bean is greater than from arabica. The
robusta variety gives thick, strong decoction. C.robusta has not been popular
in India, as the plant is susceptible to diseases and the beans have not
found favour in the market.

Production
The world production of coffee is estimated at 3 million tonnes. Though
India’s export is only about 3% of the total world export, there is a good
demand for Indian coffee because of its superior quality and use in blending.

219
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Coffee production is being introduced in the nontraditional areas of Andhra

Pradesh, Orissa and the north-eastern states.
Coffee flowers are white and sweet smelling, producing green berries
which turn red when ripe. The berry contains mucilagenous pulp with 2
greenish grey seeds or beans, each covered by a thin membrane, the silver
skin, and both are enclosed in a common husk-like membrane or parch¬
ment. Sometimes a single bean fills the berry instead of 2, when the seed is
called a peaberry, since it is like a pea. The berries are picked when ripe.
Unripe berries give defective beans (triage) and over-ripe ones are difficult to
beat to a pulp.

Processing
Coffee processing consists of removing the skin, pulp parchment and
silver skin. The quality of the final product depends on the manner of process¬
ing. Two methods are employed for processing, viz. the dry and the wet
(washed cofee process) methods. In the former method, the berries are sun-
dried by spreading them out on drying floors and the coverings are removed
by hulling. The beans are later cured in curing sheds. The product obtained
is known in trade as cherry or native coffee. In the wet method, the ripe
fruits are squeezed in a pulping machine which removes the soft outer pulp,
leaving a slippery exposed layer of mucilage. The mucilage is removed by
spontaneous fermentation. This is sometimes facilitated with added enzymes.
The seeds separating from the pulp are washed and subsequently dried to
12% moisture content. The wet method results in better quality coffee with
a bluish-green colour (green coffee). The green seeds are then graded and
packed. Green coffee may be stored for prolonged periods with no adverse
effects.
Each variety of coffee has its own flavour and other characteristics.
Generally, marketed coffee is a blend of different varieties of coffee beans.
The blends are controlled for flavour, aroma, colour and strength of body of
the beverage from the roasted beans.
Roasting
Raw of green coffee has no flavour or aroma and has an unpleasant
taste. For use as a beverage, it is roasted, powdered, and brewed and the
aqueous extract used as a beverage with or without the addition of milk,
sugar and other substances. During roasting many physical and chemical
changes occur. The beans swell to almost double their original size, the
dull-green colour changes to brown and the characteristic coffee aroma de¬
velops. The beans lose their hard horny structure and become brittle, with
the outer surface still smooth and firm. During roasting, pressure develops
in the beans and this appears to be necessary for the proper development of
coffee flavour. It is said that pressure holds the initial breakdown products
together until the proper stage of roasting is reached when they react with
each other to produce coffee flavour. The flavour is due to a mixture of

220
 BEVERAGES

numerous components rather than a definite chemical entity and is appar¬

ently produced during roasting. Some moisture is lost during roasting and
carbondioxide is produced in a comparative large quantity, some of it escap¬
ing and some being absorbed within the texture of the roasted bean. Carbo¬
hydrates decompose, caramelize and, perhaps in combination with other
substance, contribute to the aroma of the beverage produced from the roasted
beans. Fatty constituents are also affected, volatile fatty acids are driven off
and complex fats and waxes are cracked to form simple ones. Proteins may
be hydrolyzed and give cleavage products. There is a little change in the
caffeine content of coffee during roasting.
The flavour of roasted coffee, to a large extent, depends on the manner
and extent of roasting. The flavour and aroma of coffee are best when it is
freshly roasted and deteriorate on standing. Coffee exposed to air changes
more rapidly than coffee not exposed. The staleness of coffee exposed to air
is due to the oxidative changes that take place with certain coffee constitu¬
ents. This is prevented by the presence of carbondioxide in roasted coffee.
On storage, carbondioxide is lost and so are the flavour and aroma. Mois¬
ture also has a profound effect on the flavour of coffee. Coffee exposed to
moisture loses all its flavour in a relatively short time. The loss of flavour in
vaccum-packed coffee or coffee packed under pressure using carbondioxide
is less. Since the loss of flavour in a relatively short time. The loss of flavour
in vaccum packed coffee or coffee packed under pressure using carbon di¬
oxide is less. Since the loss of flavour and aroma is more in ground coffee
than in beans, the roasted beans should be freshly ground to obtain quality
coffee. In spite of many investigations, it has not been possible to clearly
understand the many complex physical and chemical changes taking place
during the roasting of coffee beans.

Chemical composition of coffee

The constiuents of coffee that are important in making a good beverage
are the flavour substances, the bitter substances, and caffeine which is
responsible for the stimulating effect of the drink (CSIR, New Delhi, 1950).
Caffeine is present in the coffee bean in both free and combined states.
Its content in the bean varies in different species, i.e. C. arabica contains
1.0-1.2, C. robusta 1.5-2.5 and C. liberica 1.4-1.6%. There is a variation in
the amount of caffeine in seeds of the same species from different parts of
the world. Caffeine, in addition to stimulation, also contributes to the bitter¬
ness of the coffee. The caffeine content of a cup of coffee (150 ml) is about
100 mg. Most people consume 3 cups of coffee a day and thus 300 mg
caffeine. While caffeine is a stimulant, its excess use causes undesirable
effects on mental and physical health. By chemical methods, most of the
caffeine can be removed from green coffee. Decaffeinated coffee retains most
of the characteristic aroma of coffee.
Several organic acids are present in aqueous extract from green coffee

221
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

beans, the predominant being chlorogenic acid and the least acetic acid.
During roasting, formic and acetic acid contents are increased and
chlorogenic and other acids like citric and malic are partially destroyed. The
pH of the coffee brew comes down. Acidity affects coffee flavour, the more
acid tasting the coffee, the better are the flavour and aroma. Beans of C.
robusta produce coffee beverage that is less acid-tasting than the arabica-
coffee beverage and is generally less desirable so far as taste is concerned.
As already indicated the flavour of roasted coffee is due to a number of
components to which the name coffeol has been given. More than 600 vola¬
tile compounds have been identified in roasted coffee. Low-boiling sulphur
compounds in coffee are the main flavour contributors (chlorogenic acid
contributes to the body and astringency of the coffee beverage, and its de¬
composition products contribute to the aroma of coffee). The breakdown
products of sugars contribute much to the colour of the beverage and also to
some extent the aroma, bitterness and sourness. Protein decomposition
compounds seem to be the major precursors of coffee aroma.
Polyphenolic substances (tannins) present in coffee contribute to the
bitterness of coffee beverage. They are readily soluble at the boiling tem¬
perature of water. They are also present in other substances, extracted on
boiling, that contribute to the bitter taste and combine with certain metallic
salts to give a metallic flavour to the beverage.

Coffee making
Coffee, fresh from the roaster and ground fresh, makes a good bever¬
age. It is not possible to roast coffee fresh. It is better to buy small quantities
of the powder and keep it covered to exclude air and moisture. The beverage
is at its best when freshly brewed. If it is cooled and reheated, it becomes
bitter and unpleasant.
Coffee is ground and marketed to meet a range of brewing methods.
The basic grinds are fine, medium and coarse. A variation can be found
within each of these categories. Fine grind is used in vaccum coffee makers;
medium or drip grind is used for making coffee in a drip pot or by steeping;
and coarse grind is used in a percolater. It is always best to match the grind
to the coffee making equipment to obtain a good-quality beverage.
Preparation of coffee beverage of high quality requires that the extrac¬
tion of caffeine and flavouring materials be maximum and that of tannin
minimum. Different methods are used to obtain this objective. The methods
differ in type of utensils used and the ground coffee, but they are all based
on the principle of bringing ground coffee in contact with hot water to ex¬
tract the soluble constituents. Whatever the method employed, vessels used
to prepare coffee must be very clean. The material used for coffee making is
important. Some metals influence the flavour of the beverage. Stainless
steel, glassware and enamelware are preferred. Water used in coffee mak¬
ing should be soft or of low hardness. A temperature between 85° and 95°C

222
 BEVERAGES

is optimum for preparing coffee. If the water is heated to boiling point, it

over-extracts soluble solids and the beverage is bitter, and there is also a
loss of flavour substances. However, pouring boiling water on the coffee
poweder is permissible, as the temperature drops as soon as the water comes
in contact with the grind.

Vacuum coffee
Vacuum coffee is made in a two-part container. The upper compart¬
ment holding the coffee has an open tube that extends to the bottom of the
lower compartment containing water. By heating water in lower compart¬
ment, sufficient pressure is created in the bottom container to force water
through the coffee grind into the upper compartment. When the water and
grounds are in contact for about 3 min, the heat is reduced on the lower
compartment resulting in a reduced pressure and the brewed coffee is pulled
down to the bottom compartment. Powedered coffee is usually prevented
from pouring into the lower compartment by the use of cloth covered disk,
held in place over the tube opening. The advantage of vacuum coffee is its
convenient preparation; its disadvantage is that the coffee prepared thus is
slightly bitter because the water and grounds are in contact for a few min¬
utes at a high temperature.

Drip coffee
Drip coffee is made in a dripolator (coffee filter) consisting of an upper
compartment which is perforated and a lower compartment which receives
the filtered coffee. The perforation of the upper compartment is covered
with a thin cheese cloth or a perforated disc with a stem, to prevent the
passage of the grind into the beverage. Drip grind coffee is placed in upper
compartment and boiled water poured into the compartment. The water
drips or flows through coffee into the lower compartment. The drip method
is easy and is used widely. This method extracts less of the bitter sub¬
stances and retains more flavour constituents than other methods.

Percolator coffee
Percolator coffee is made by placing coarse ground coffee in a basket
suspended in a stem near the top of the percolator and is inserted into the
percolator. Cold water is placed in the lower part of the percolator and heated.
The heated water is forced up the tube of the percolator and sprays on the
grounds, extracting the soluble materials. The usual percolation time is 6-8
min. Percolator coffee is likely to be somewhat bitter because very hot water
passes through the grounds several times. Also, the constant aeration of the
brew as the liquid is forced up and the sprayed over the grounds results in
loss of flavour.

Steeped coffee
This coffee (misnamed as boiled coffee) is made by heating water and

223
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

medium ground coffee, without allowing it to boil. If coffee is boiled it be¬

comes bitter. Steeping time is about 6-8 min. During steeping coffee pot
should be lightly covered to prevent loss of volatile flavouring compounds.
The coffee is then passed through a strainer. This method of making coffee
is convenient, as no special equipment is required. If care is taken not to
boil it, the beverage will have good aroma, desirable flavour and will not be
bitter.

Espresso coffee
This is made by a special machine which brews the beverage a cup at a
time. It is derived from brewing finely ground coffee with a mixture of steam
and hot water.

Iced coffee
This is made by pouring a freshly made strong coffee infusion over
crushed ice. The infusion is obtained by using more of coffee grounds per
cup. This offsets the dilution that takes place as the ice melts in the hot
beverage, resulting in a pleasing beverage with a distinctive flavour.

Soluble coffee
Soluble coffee is a dry, powdered, water-soluble solid made from very
strong coffee brew. It is marketed as instant and freeze-dried coffee. Instant
coffee is made by the vacuum spray drying of the brew from the ground
coffee, obtained from the percolation method. Freeze-dried coffee is made
by first freezing the strong brewed coffee and then drying by vaporization in
vacuum.Instant coffee has a flavour similar to freshly brewed coffee but
lacks aroma of fresh beverage. Attempts are being made to improve aroma
by using additives. Freeze-dried coffee is being obtained in granulated form,
the particle size being roughly that of ground coffee. Attempts to recover the
volatile aromatic substances lost during the processing of the coffee brew
and adding them to freeze dried coffee to obtain a product with an aroma
similar to that of freshly brewed coffee have been sucessful. Though India is
producing and exporting instant coffee, we have not yet made freeze-dried
and granulated coffee. The world export of soluble coffee amounts to around
300.000 tonnes of green coffee equivalent.

CHICORY (CICHORIUM INTYBUS)

It is a well-known substitute for coffee, often used blended (up to 50%)

with the latter, in liquid-coffee extracts. Chicory gives bitterness to the bev¬
erage, which some people find refreshing. The part of the plant used is the
root which is chopped, roasted and ground.

TEA (CAMELLIA SINENSIS)

Tea is an evergreen shrub or tree, which grows wild from India to China.

224 |
 BEVERAGES

There are about 45 species of Camellia of which sinensis considered native

to India, is the important one from which tea of commerce is made. Com¬
mercial tea is obtained from plants propagated by seed sown in a nursery;
cuttings can also be rooted. Trees for plucking are regularly pruned to obtain
a bush shape, which encourages maximum leaf production. Amongst culti¬
vated, C. sinersis are of 2 types, viz. China and Indian. The former type is a
slow-growing smaller tree with narrow leaves, whereas the latter is fast grow¬
ing with large drooping leaves. The yield from Indian types is higher than
that of the China type. The important tea growing countries are India, China,
Sri Lanka, Japan and Kenya.
Tea leaves are usually plucked by hand. The average interval between
pluckings is about a week. In India, about 5-6 pluckings are made in a
season. Usually, the terminal bud and 2 terminal leaves from the end of
each shoot are plucked. In some cases, the bud and 3 leaves are taken
giving a higher yield and a poorer quality product. Some of the best tea
come from high-altitude areas, such as Darjeeling, while tea from the plains
is often of common quality. The yield at high elevation is poor than to that at
lower elevation for the same kind of plant.
The manufactured tea that comes into the market can be divided into 4
groups with respect to the production technology used. This classification is
strictly speaking, based on the use of enzymes in the course of raw tea
treatment (Alok et al, 1996). An application of enzymes throughout the
entire process, that includes withering and fermenting stage, yields the so
called fermented tea, which includes all brands and grades of black tea
(including instant black tea). An asset of enzyme activity at an early stage of
tea processing, by steaming or roasting raw tea yields the so called
unfermented tea which includes different brands and grades of green tea
with a specific taste and aroma, including green brick and green instant
teas. A partial utilization of about 20-30% enzymes of tea combines with
thermal treatment yielding the so-called red tea, or oolong tea, with a rich
and strong aroma, reddish infusion and pleasant taste.

Processing
Commercial tea is available mainly in 3 forms, viz. black tea, green tea
and oollong tea. These forms of tea differ only in the method of processing
the leaves. Black tea is by far the most popular among the three.

Black tea
The various processing steps in the manufacture of black tea are with¬
ering, rolling, fermentation, drying, grading and packing. Withering is car¬
ried out by spreading tea leaves thinly on racks or shelves, to dry the leaves
partially. Generally withering is allowed till the water content in the leaf is
lowered by about 40%. The withered leaves are then rolled to break open
the cells and release the juices and enzymes. Various rolling techniques are
employed and the flavour characteristics inherent in various types of tea

225
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

partially depends on the techniques employed and the flavour characteris¬

tics inherent in various types of tea partially depend on the technique used.
After rolling, the leaves are shifted and spread out thinly on suitable plat¬
forms and allowed to ferment for 2-6 hr at temperatures between 21°-27°C.
During this process, the enzymes cause the oxidation of various polyphenols
present in juices, resulting in the change of colour from green to reddish
copper. Two of the important polyphenols that undergo oxidative changes
are catechin and gallocatechin.
When the fermentation has proceeded to the desired degree, further
change is arrested by drying or firing. This comprises passing of fermented
leaves through a chamber in which hot air is circulating. At the entrance of
the chamber, the temperature is 93°C which drops to about 49°C near the
exit. The time required for this process is about 30-40 min and the dried
production contains 3-4% moisture. Besides halting the fermentation proc¬
ess, firing causes some caramelization to occur resulting in the characteris¬
tic colour of black tea leaves.
The aroma of tea is believed to develop during the fermentation and
firing processes. Althogh a large number of volatile compounds have been
identified from tea leaves, none has been found to make any significant
contribution to the tea aroma.
The dried product is cleaned and sorted into various grades of tea of
commerce. The quality of black tea is related to the polyphenol and enzyme
content of the leaves used in processing. They are maximum in buds and
the first and the second leaves (28, and 27% respectively) and types of tea
obtained from these are the most desirable. On this basis tea is categorized
as leaf and broken grade. The broken grade comprises smaller size sifted
from bulk or those obtained by cutting the longer leaf grades to desirable
sizes. Both leaf and broken grades are further categorized as orange pekoe,
pekoe and souchang. Orange pekoe and pekoe refer to the size of the leaf
only. Orange pekoe has the largest leaves, followed by pekoe and souchang
in decresing order. Orange pekoe is perhaps the best quality. Other things
being equal, the broken grade usually gives a stronger tea than leaf grade.
Besides the above grade, there are the waste products fannings and dustings.
Tea is generally blended before it reaches the consumer. In India, the
blended tea is packed in plywood boxes lined with aluminium foil and parch¬
ment paper. During packing, tea absorbs moisture. If the moisture content
increases to 6-7%, tea is to be subjected to a second firing before packing.
India is also exporting tea in consumer tea packs instead of bulk tea chests.

Green tea
Green tea is made in the same manner as black tea, but the withering
and fermentation steps are omitted. The leaves are treated with heat, rolled
and dried. The head treatment consists of pan firing or steaming to inacti¬
vate enzymes. Aroma, flavour and colour of green tea are significantly dif-

226
 BEVERAGES

ferent from those of black tea. Green tea is a light, yellow green beverage
when brewed correctly. Japanese mainly produce and consume green tea.

Oolong tea
Oolong tea is an intermediate between black and green tea in colour
and taste. Its production method is similar to green tea, except that the leaf
is slightly withered and light fermentation allowed before leaf is dried.

Composition of tea
The important constituents of tea contributing to flavour of tea bever¬
age are caffeine, polyphenols and essential oils. Analysis of fresh tea leaves
shows polyphenols 22.2, protein 17.2, caffeine 4.3, crude fibre 27.0, starch
0.5 and ash 5.6%, little amount of carotenes, B-vitamin and ascorbic acid.
During manufacturing of black tea, asorbic acid is lost.
The maximum amount of caffeine is present in the terminal bud and
the first 2 leaves, small quantities of compounds related to caffeine, viz,
theophylline, theobromine, xanthine and hypoxanthine, are also present.
The important polyphenols present in tea leaves are catechins and
glallocatechins. These undergo change during fermentation in manufacture
of black tea. Enzymes involved in fermentation are polyphenol oxidases. No
change takes place in green tea, as its manufacture does not involve fer¬
mentation. During fermentation, poyphenols undergo oxidation and oxi¬
dized products polymerize and part of them combine with caffeine. The
caffeine-polyphenol complexes are soluble only in hot water and this ac¬
counts for the creaming observed when not tea infusions are cooled. Tea
leaves contain a volatile oil consisting of alcohols, aldehydes, phenols and
some fatty acids. On steam distillation, black tea gives an essential oil. The
characteristic aroma and flavour of tea is due to the essential oil. Tea, like
coffee, has no nutritive value. The proteins present in tea leaves are ren¬
dered insoluble in the processing. Tea infusion contains negligible quanti¬
ties of Carbohydrates and fat.Whatever nutritive value tea has comes from
added milk and sugar. Tea as a beverage is consumed mainly for its stimu¬
lating value.

Preparation of tea
A good cup of tea will be sprakingly clear and not have a surface film. It
should have maximum flavour with minimum polyphenol compounds which
contribute to bitterness. In order to obtain this, water, used in making tea
should be fresh and soft. If water is hard, the dissolved salts form an unde¬
sirable precipitate with polyphenols and this will be present as an unattrac¬
tive film that floats on the surface of tea. The water should be freshly boiled
but still contain sufficient oxygen to give the tea a fresh and pleasant odour.
Metallic tea pots impart a metallic flavour. It is best to use china, glass or
enamelled ware. Water heated to 85°C to boiling should be added to the

227
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

appropriate amount of tea (generally 1 teaspoonful for 150 ml contained in

the pot). The pot should be covered with a lid which helps retain heat and
prevents excape of volatile compounds. Flavour substances and caffeine are
readily extracted by short infusion periods. Generally, a steeping period of
about 3 min. gives a stimulating, but not astringent, beverage. A very con¬
venient method of making tea is the tea-ball or bag method. In this method,
water at the boiling temperature is poured over tea contained in a cheese
cloth or paper bag or a silver ball. The bag or ball is allowed to remain in
contact with water till the desired strength is obtained. Milk or lemon may
be added to the tea infusion for body and flavour, and sugar for taste.

Iced tea
Iced tea is popular in some countries. Hot tea is prepared in the usual
way by using twice as much tea leaves. It is throughly chilled before pouring
over ice. It may also be poured over ice while it is still hot. This will result in
a beverage which dilute to normal strength as ice melts. Cloudiness is gen¬
erally problem with iced tea, as tannins precipitate when tea cools.

Instant tea
Instant tea (soluble tea) products have become popular in recent times.
These products are hot and cold water solubles, iced tea concentrates, car¬
bonated tea etc. In the preparation of hot water soluble instant tea, the
fermented tea leaves are extracted with hot water, centrifuged and dried in
drum drier or freeze drier. For the manufacture of cold water soluble tea,
the aqueous extract is cooled to 5°C, the separated caffeine-polyphenol com¬
pound is removed by centrifugation and then dried. Iced tea concentrate is
cold water soluble and contains sugar, citric acid and essences. Ready tea is
instant tea with sugar and milk poweder. India produces all these varieties
of instant tea and sizeable quantities are exported.
Instant tea is largely used in making iced tea because of its solubility in
cold water. However, the flavour and aroma of instant tea is less full than
that of the beverage freshly prepared from tea leaves.

COCOA (THEOBROMA CACAO)

Cocoa plant is a small tree native to American tropics. It is now grown in all
tropical regions of the world. The chief cocoa-producing countries of world
are Ghana, Nigeria, Ivory Coast and Brazil. Cocoa was introduced to India
from Sri Lanka and is comparatively a new crop. Its production is fast pick¬
ing up and it is grown in Kerala, Karnataka and to some extent in Tamil
Nadu. Cocoa tree has unusual habit, like the jackfruit tree, of bearing its
flowering and, subsquently, its pods on the main trunk as well as on the
branches. Cocoa pods, when mature, are yellow in some varieties and red in
others. The pods are 10 to 18 cm in diameter, having thick leathery rinds
containing 20-50 beans inside in rows. The seeds are embedded in white or

228
 BEVERAGES

pinkish pulp. Seeds are the principal source of cocoa or cocoa powder highly
prized as a nutritious beverage, and chocolate used as food all the world
over.
Production
The world production of cocoa is about 1.9 million tonnes. The demand
for cocoa products till recently was mainly met by imports. We have been
importing about 1,000 tonnes of cocoa bean a year and some of the imported
cocoa is re-exported as cocoa powder, chocolates, cocoa butter, etc. We are
becoming self-sufficient and are at the stage of discontinuing imports.
Processing
Cocoa pods, after harvesting, are cautiously opened. The beans and
mucilage are scooped out and subjected to natural fermentation either in
heaps, wooden boxes (sweat boxes) or baskets. Fermentation generally takes
5-10 days. At the end of fermentation, the pulp breaks down and there is a
change in the colour of the seeds from pale yellow or voilet to brown. The
endogenous enzymes, activated by the heat of fermentation, bring about
changes in proteins and polyphenols in the kernel and there is also a reduc¬
tion in the astringency of the kernel. The beans are then dried to 6-8%
moisture level under the sun or in artificial dryers. The bean is then ready
for export or further processing to manufacture cocoa products.
The dried beans are cleaned, sorted and roasted. Roasting develops
characteristic flavour. Although a large number of compounds have been
identified in cocoa and chocolate, no single constituent is found responsible
for the characteristic subtle aroma. Roasting also causes changes in chemical
structure of polyphenols, producing less astringent compounds. While roast¬
ing, the beans are passed through corrugated rollers to break their shells
and removed by winnowing. The cotyledons are known as nibs. Usually
there is some blending of the nibs different varieties of cocoa before they are
processed further.
The nibs are used for the manufacture of cocoa and chocolate. The nibs
are ground using stone mills or other suitable mills to a fine paste or liquor.
The heat produced during grinding causes cocoa fat to melt and the melted
fat carries with it in suspension, finely ground particles of cocoa. This is
known as cocoa mass, chocolate liquor or bitter chocolate. This mass solidifies
at about 30°C.
Cocoa mass is very rich (50-55%) in fat and cannot be used directly for
the preparation of any beverage. It is subjected to filter-pressing to separate
out a major part of fat (cocoa butter). The amount of fat left in the pressed
cake can be varied by conditions of pressing. The pressed cake is used for
producing cocoa powder. According to the Bureau of Indian Standards (BSI)
specifications, cocoa used for beverage should contain 20% cocoa fat. Me¬
dium-fat cocoa, containing 10-20% fat and low-fat cocoa, containing less
than 10% fat are made. Flavouring substances like vanilla and cinnamon
are generally incorporated into cocoa powder.

229
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

The pressed cake, after removal of cocoa butter, contains 1.8-1.13%

free acids. In one of the methods of cocoa processing the acid is neutralized
with the addition of a requiste amount of alkali. This is known as the Dutch
process, because it originated in Holland. Cocoa processed by this method
is dark in colour and the flavour will be somewhat more bitter and astrin¬
gent than the same material not treated with alkali.

Chocolate
Cocoa mass not treated with alkali is generally used for manufacture of
chocolate. There are many types of chocolate depending on level of cocoa
mass, added cocoa butter, sugar, milk and other ingredients. Plain choco¬
late (sweet chocolate) is cocoa mass processed with cocoa butter and sugar.
Milk chocolate contains, in addition to these ingredients of plain chocolate,
milk solids. Plain chocolate contains 40-55% sugar and 32-42% fat, while
milk chocolate contains 35-55% sugar, 28-39% fat and 12% milk solids.
Plain and milk chocolate are extensively used in confectionery and icecream.
Composition: The analysis of cocoa beans (processed) shows moisture
2.13, fat, 54.68, total nitrogen 2.16, starch 6.14, pentosans 11.19 and tanins
6.15%. The theobromine content of cocoa is high (about 2.8%). Cocoa is the
natural source of theobromine. There is some loss of theobromine content
during fermentation and roasting. Cocoa also contains caffeine (about 0.6%).
The proteins of cocoa bean are present in combination with polyphenols.
Unlike coffee and tea, which are strained forms of beverage, cocoa and choco¬
late remain in the beverage and contribute to the nutritive value of the
beverage (Shakunthala and Shadaksharaswamy, 1987).

Cocoa beverages
Cocoa and chocolate, apart from their many uses in cooking, find ex¬
tensive use in the preparation of beverages. When chocolate is used, it sticks
to container and gets scorches when heated. This can be eliminated by
heating chocolate over hot water or by heating it at a low temperature. The
melted chocolate is then blended with other ingredients. Owing to its high
starch content, cocoa will lump if put directly into a hot liquid. It should be
mixed with a small amount of cold liquid before being combined with other
ingredients. Cocoa and chocolate thus treated are heated to boiling and
held at that temperature for sometime to gelatinize the starch. This gives
body and flavour to the beverage and reduces amount of sediment that
settles from either of the beverages. Apart from coffee, tea and cocoa, a
number of preparations are available in market which are consumed as hot
drinks. While the former group of beverages are stimulants the latter are
energy food and are consumed as supplementary foods to regular diet. They
contain mainly malted cereals, creamy milk, sugar and artificial flavour,
and sometimes are fortified with nutrients and minerals. Some prepara¬
tions also contain cocoa. The drink is prepared by stirring the material in
warm water or milk and is generally consumed as hot drink; but could also
be used as a cold drink.
230
 BEVERAGES

SOFT DRINKS

Soft drinks constitute one of the largest food industries in the world today.
Tremendous advances have taken place in process technology in the soft
drink industry in the past one or two decades. In India, in the organized
sector alone, annual production of soft beverage is about 45 million litres.
The flavoured component of most of the well-known brands of soft drinks is
a well-guarded secret. The most popular soft drinks sold throughout the
world today are cola (an extract from the tree cola), orange, root beer, gin¬
ger, lemon and lime. Most of the cold drinks in the country belong to this
class. Soft drinks are divided into 3 classess: carbonated, fruit flavoured
(still) and sparkling (soda water). The carbonated beverages, in turn, are
divided into 2 groups, those with artificial flavour and those with natural
fruit juice.

Ingredients
The major ingredients of soft drinks are: (i) sugar and sugar substi¬
tutes, (iz) flavour emulsion and cloudifiers, (in) colouring agents, (iv) acids
and preservatives, (v) water and (n) carbondioxide. A quality soft drink should
have a balanced blend of flavour at the proper intensity leaving a clean
mouth taste with no lingering flavour or unpleasant after taste and should
have proper carbonation to impart zest and sparkle to the drink
The process of manufacturing carbonated beverages consists of several
steps. Syrup is prepared from sugar or substitutes and water. To the syrup,
acid, colour and flavouring agents are added as required. The components
are blended. A suitable aliquot of the mixture is diluted with chilled carbon¬
ated water and bottled. Alternatively, ready syrup is diluted, chilled, car¬
bonated and then filled in the bottle. The bottles are then capped, labelled
and marketed.
Sugar
Sugar and sugar substitutes contribute sweetness necessary to bal¬
ance various ingredients, give body and mouth feel and also act as carriers
to distribute flavour components uniformly throughout the drinks. Sugar
component also contributes to the food value of the beverage and to some
extent to the flavour. Sucrose is the most widely used sweetening agent.
Some sweetening agents like cyclamates which were being used formerly
are now banned as they are found to be harmful. Because of the high cost of
crystalline sugar, sugar syrups are used as sweetners. Fructose syrup (proc¬
essed from corn starch) or high fructose corn syrup (HFCS) are used these
days. A 55% fructose corn syrup has approximately the same sweetness as
sucrose, while 90% fructose syrup is approximately 50% more sweet than
sucrose. Use of fructose syrup in soft drink manufacture has other advantges;
it permits substantial reduction in calorie content of the drink and it also
reduces cost of the drink. Fructose syrup is not yet available in India.

231
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Flavouring materials
Three types of flavouring materials are used in soft drinks (z) those ob¬
tained from natural sources, such as fruit concentrates or extracts from
natural flavour materials; (zz) synthetic compounds identical to those ob¬
tained from natural products; and (zzz) synthetic chemical not found in na¬
ture. Most flavours, however, are wholly natural or a blend of natural and
synthetic material identical to those found in nature. The flavouring agents
should have complete solubility, compatibility, clean mouthfeel without an
after taste, resistant to acid and heat, and stable to light. Flavours are used
generally emulsified in vegetable gums. This prevents the flavour substances
(particularly oils) from separating out in the beverages.
Colouring materials
These are used in soft drinks in order to maintain a uniform colour in
the beverage from batch to batch. In some cases colour is derived from
flavouring substance used. Generally, synthetic food colours and natural
colouring ingredients like caramel are used. Caramel in beverages gives
them a dark to light brown colour and is usually associated with flavour of
the type derived from roots, leaves, herbs and berries.
Acids and preservatives
Acids, in addition to taste enhance the flavour of soft drinks. The acid
most widely used is citric acid. Other acids used in considerable quantities
are tartaric and phosphoric acids. Lactic and malic acids are also used in
lesser amounts. Citric acid (present in citrus fruits) adopts itself well to
nearly all light and fruity flavours. Phosphoric acid is used in beverages
with leaf, root, nut or herbal flavours. Tartaric acid (present in grapes) is
used in grape flavours. The acids, besides giving taste and flavour, also act
as mild preservatives. However, to ensure against spoilage, sodium benzoate
is commonly used as a preservative.
Water
Water constitutes the largest (about 92%) component of soft drinks.
Water used in beverage manufacture must be free from suspended matter
and colouring matter. It should not contain minerals which would interfere
with the flavour and colour of the beverage. It should also be free from
objectionable odours. Thus, water used should conform to the specification
set for beverages.
Carbondioxide
Carbondioxide is an important constituent of soft drinks. The gas used
must be absolutely pure. It enhances the flavour of the beverage and gives
it its sparkle. It also extends the life of drink. The level of carbonation is
determined by flavour component and quality of flavour.

ALCOHOLIC BEVERAGES

Alcoholic beverages have been known since antiquity. These are judged in
terms of flavour and stimulant effect and hardly at all as sources of calories.

232
 BEVERAGES

However, the calorific value of alcohol in 7 Kcal/g and excess of alcohol

consumed could add to the total calorie intake of a person. In the case of the
distilled liquors (whisky, brandy, gin and rum), the calorific value is only
due to alcohol and consumption of 100 ml of these beverages would yield
about 230 Kcal of energy. Beer and wine contain some nutrients present in
the original malted barley and the fruit juice used in their preparation and
naturally their energy value would be higher than that of distilled liquors;
350 ml of beer gives about 150 Kcal and 100 ml of wine about 80 Kcal.
Alcohol is absorbed without prior digestion but the body has limited
capacity to oxidize it. Hence alcoholic beverages are to be sipped instead of
gulping them. As a drug the effects of alcohol vary from mild stimulation,
when small amounts are consumed to loss of coordination and even death
when large amounts are consumed.
There are 3 main classes of alcoholic beverage wines, malted beverages
(beer) and distilled liquors. Different starting materials and different meth¬
ods are used in their manufacture. But there is one common characteristic
in all of them, viz. they are made by the process of fermentation. The essen¬
tial step in all the fermentation processes is the conversion of glucose into
alcohol by yeast. The enzymes present in yeast catalyze the breakdown of
g‘ucose- Yeast enzymes
C6H1206 ->2C2H50H+2C02

Wines
Wines are the oldest of the alcoholic beverages made by the fermenta¬
tion of grape juice. Wine, stricitly speaking, is a product of vine, but often
includes all fermented liquors obtained from different fruit juices (fruit wines).
Wines differ greatly in their character, because grapes grown in different
regions differ in their composition, particularly in their volatile components
which contribute to flavour and bouquet and in the method used for wine
making (Amerine, 1972; Amerine etal, 1972; Cruess, 1947).
There are different varieties of wines and in many cases they are named
by reference to their place of origin, eg, champagne is produced in the dis¬
trict of Champagne in France. Most of the wines produced in the world are
natural and still (without excess of carbondioxide). Sparkling wines, such
as champagne, contain excess of carbondioxide due to secondary fermenta¬
tion that occurs after bottling. The carbondioxide generated is stored within
the liquid under its own pressure and gives the wine a sparkle. Some wines
like port and sherry are fortified wines and differ from natural wines in that
some alcohol (grape brandy) is added to them before the completion of fer¬
mentation. Vermouth is also a fortified wine prepared by the addition of
spice mixtures or their extracts at various stages during fermentation (Joe
and Shaheni, 1975; Rice, 1973).
Wines also differ in their colour. The colour of wine may be white or red.
However, the colour does not depend on the colour of the grapes from which

233
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

it is made; in fact, white wines may easily be made from black grapes by
using only the juice. In making red wines both juice and skin are used; the
pigment giving colour to the grapes lies just under the skin and is extracted
from it during fermentation. Wines may be either dry or sweet depending on
the extent to which the fermentation has taken place. If fermentation has
taken place until all the sugar is used up, the resulting wine will be dry;
whereas if it is stopped while some sugar remains, it will be sweet. Yeast
cannot tolerate an alcohol content greater than 16%. Most of the natural
wines contain 8-10% alcohol. Fortified wines contain about 20% alcohol,
which is sufficiently high to kill the microorganisms that attack natural
wines. Wines containing less than 14% alcohol are table wines, whereas
those containing more are dessert wines.
In the manufacture of wine, grapes are picked at the proper time when
the sugar and acid contents are in right proportion. The composition of the
grapes varies according to the climatic conditions prevailing during their
cultivation and thus the quality of wine varies from year to year. Therefore,
there is the practice of vintage dating, the wine with the year of the crop
from which it is made. Immediately after picking, in the case of red wines,
grapes are crushed and juice together with the skin, pulp and seeds are
transferred to fermentors.After fermentation is completed, the fermented
juice is pressed out. In the case of white wines, pressing takes place before
fermentation.
Wild yeast and other microorganisms are present on skin of grapes and
these pass into juicy pulp (known as must) when the fruit is crushed. These
are destroyed by adding sulphurdioxide (or potassium metabisulphite) in
the required quantity. If the sugar content is low sucrose is added to the
desired strength and pH is adjusted to 3.2-3.4 by the addition of tartaric
acid. Next, the must is inoculated with a pure culture of actively growing
yeast (Saccharomyces ellipsoideus). The temperature and duration of fer¬
mentation depend on whether dry or sweet wine is required. Fermentation
usually lasts 4 to 10 days. Table wines have a comparatively low content of
alcohol and little or no sugar, while dessert wines are fortified sweet wines.
On complete fermentation, the clear wine is symphoned from the yeast
sediment into barrels (raking) and the wine allowed to age. During this
period secondary fermentation takes place and the wine also loses its raw
and harsh flavour and mellows down. During this period of maturation clari¬
fication takes place in the natural way. It can also be achieved by finning
and filtration. Next, the wine is bottled and allowed to mature; the time of
this maturation extends to a number of years, depending on quality de¬
sired.
Wines are also made from juices of other fruits and berries. Cider is
fermented apple juice. The method of fermentation with fruit juices other
than of grapes is almost similar to that of preparation of grape wine. French
dry sherry is made from grapes which have a high sugar content. The other

234
 BEVERAGES

wines are perry wine made from pears and mead (honey wine) made from
diluted honey (Frazier and Westhott, 1995).
Beer
Beer, next to wine, is the oldest alcoholic beverage to have been made.
There are evidences of existance of fermented beverage from barley in Indus
Valley civilization about 5000 years ago, and in China, Egypt and other
countries even earlier. The first brewery in India was started in 1860, and in
1981 there were 29 breweries and the beer production was about 1.7 mil¬
lion hectolitres, which is very insignificant compared with a world production
of 960 million hectolitres in the same year. The chief beer producing countries
in the world are the USA, FDR, USSR, UK and Japan.
The term beer is normally applied to a beverage made by the fermenta¬
tion of barley malt. However, terms like ale, stout, lager and porter are also
used for beer, the difference between them being the method of production.
The materials used in the manufacture of beer are barley, malt cereal adjunct,
hops, water and yeast. The principal operations involved in the production
of beer are malting, mashing and fermentation. The starting material for
the production of beer is barley malt. For malting of barley see part III,
millets.
Starchy materials that are cheaper than malt are used as adjuncts to
replace some malt. The most commonly used cereal adjunct is maize in the
form of grits or flakes. Other adjuncts suitable for brewing are broken rice,
wheat, raw barley, tapioca, starch and sorghum. Such adjuncts should not
impede the fermentation process or have an undesirable effect on the qual¬
ity of the product. The entire starch of the adjunct is to be converted into
sugar. Thus, the percentage of adjunct that can be added is restricted by
the amount of enzymes in the malt. The introduction of microbial enzymes
has increased the flexibility of varying adjunct proportion, as these exzymes
supplement malt enzymes. They also reduce the cost of raw material and
maintain the quality of beer. Liquid syrup adjuncts can also be used, but
they are yet to enter the brewing field in India.
Suitablity of water for brewing is of great importance in beer making.
Water should be hard, and if soft, salts are added to the required hardness.
If the water is too hard, it may have to be boiled to remove most of the
temperary hardness.
The yeast used depends on the type of beer to be manufactured. For the
production of ale, top fermentation systems are used with the yeast
Sacharomyces cerevisiae. In top fermentation, the yeast is carried to the top
of the fermentating vatt by rapidly evolving bubbles of carbondioxide. For
the production of lager, the bottom fermentation system is employed with
Saccharomyces carlsbergensis. During fermentation, the yeast settles at the
bottom of the vats.
In the manufacture of beer, the malt is mashed, i.e. the ground malt is
steeped in hot water in vessels called mash tun. Two mashing methods are

235
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

generally employed, viz. infusion mashing, followed in India, and decoction

mashing. In infusion mashing, hot water at 65.5°C is mixed with ground
malt to consistency of porridge. Cereal adjuncts (gelatinized) are added to
malt grit. Sugar syrups, if desired, are also added at this stage. The period
of infusion is about 2 hr and the temperature is maintained at 65.5°C.
During this period, malt amylases degrade starch in aqueous solution to
produce sugars approximately in the following ratios: 7-10% monosaccha¬
rides, 48-55% disaccharides, 12-15% trisacharides and 20-30% dextrin.
By regulating the mashing conditions, the proportion of various carbohydrates
can be varied to suit the requirement of the beer to be brewed. When steeping
is complete, the extract known as wort is filtered off through barley husks
which settle on the perforated false bottom of the mash tun.
The wort is then boiled with hops. This boiling destroys the malt en¬
zymes and sterilizes the wort. The essential oil and bitter substances of
hops are extracted and the proteins are coagulated. The coagulation of pro¬
tein assists in clarifying the beer. The liquor is filtered through spent hops
which retain the precipitated materials. The liquor, when cold, is seeded
with yeast and allowed to ferment for a few days during which time sugar is
converted into alcohol. When the fermentation is complete, the beer is al¬
lowed to stand for 1 or 2 days when yeast settles down.
After fermentation, the beer is run-off to storage tanks for maturing
when secondary fermentation takes place and flavour and bouquet of beer
develop. The maturing process varies from only a few days for mild beer to
several months for strong beer. Next, the beer is pasteurized or sterile fil¬
tered and bottled or canned, with the introduction of carbondioxide under
pressure.
Variation in quality of beer, such as the strength of alcohol, colour and
extractives, depends on the quality of malt, malt adjuncts used, mashing
method, amount of hops added and the condition of fermentation (Broderick,
1977). Beer, ale, porter and stout are beverages produced by top fermenta¬
tion while lager beer is a product of bottom fermentation. Ale is made like
lager but is usually stronger in hop character and contains a higher alcohol
content. Porter is a heavier and darker drink made with longer dried, roasted,
or caramelized malt with less hops. Stout is like porter except that it has
heavier malt flavour much darker than any other malt drink. It has a stronger
hop taste than porter. The alcohol content of various beers varies from 2.5
to 7% by volume. Beers produced in India contain 4-5% alcohol and have a
calorific value of about 30 Kcal/100 ml (Frazier and Westhott, 1995).
Sake is Japanese beer, which is made entirely from rice. Whole grain
rice is soaked until it is quite soft and then steamed. The steamed rice is
partially dried by spreading on straw mats. It is then inoculated with a
yeast-like mould and after 10-14 days, the completely fermented material
is filtered. This fluid is placed in barrels to settle. After a few days, the clear

236
 BEVERAGES

liquid is withdrawn and pasteurized giving saki It contains about 14-17%

or more alcohol by volume (Hardwick, 1973).
Sonti is a rice beer or wine of India. The mould Rhizopus sonti and
yeasts are active in the fermentation.
Pulque is a latin-American beer like beverage containing about 6% alco¬
hol that results from a natural yeast fermentation of the juice of the agave
or century plant.
Ginger beer is a mildly alcholoic, acid beverage made by fermentation of
a sugar solution flavoured with ginger.
Pilsener is a large type beer, light in colour, containing little remaining
fermented carbohydrate.
Bock beer is a very dark beer with a high alcohol content.
Coconut sap or juice is obtained by tapping or cutting the stalk of the
young flower bunches of coconut. The main constituent of the fresh juice is
sucrose (12.3-17.4%); the juice is rich in ascorbic acid (16-30 mg/100 ml).
The juice in the fresh state is sweet toddy or neera and is used as a bever¬
age. Sweet toddy, if carefully collected in sterile vessels, remains unfermented
for a considerable time. However, as collected, fermentation gets in the fer¬
mented product toddy is used as a beverage and contains about 4.0% alco¬
hol. Arrack is the product obtained by the distillation of fermented toddy
and contains about 35% alcohol. Coconut sap when strained and evapo¬
rated gives jaggery.

Distilled spirits
Distilled spirits are made by distilling fermented liquors. Whisky is made
by the fermentation and distillation of fermented cereal grains, brandy from
wine and rum from fermented molasses. Gin is a distilled spirit flavoured
with juniper (Juniperus communis) berries or some other aromatics. Dis¬
tilled liquors usually 40% alcohol and thus have excellent keeping qualities.
Usually, distilled liquors, other than gin, are allowed to mature before con¬
sumption, e.g. whisky, are matured in wooden racks for 5-15 years to be¬
come smooth and mellow.
An essential stage in making spirits is distillation. The liquid obtained
by fermentation from different materials contains dilute alcohol and is concen¬
trated by distillation. Originally, distillation was carried out in a pot still. To
obtain a concentrated alcoholic liquor, the distillation in a pot still has to be
repeated a number of times. To overcome this disadvantage, continuous
distillation stills have been developed. In spite of this development, pot still
distillation is still used for making the finest whiskys, brandies and other
renowned spirits. Pot still allows many of the volatile components which
contribute characteristic and subtle flavours to the drink to pass over with
the alcohol during distillation. The best of brandies, cognac, is made by
distilling twice in a pot still.

237
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Whisky is made using different cereals. Scotch malt whisky, the original
whisky, is made from malted barley and scotch grain whisky from barley
malt and other unmalted cereal grains. The US whiskys are generally made
from rye (straight rye whisky) and maize (straight maize whisky). Canadian
whisky is made from maize, wheat, rye or barley. Irish whisky is made from
malted barely alone or with a mixture of unmalted barely, wheat, rye and
oats.
In the manufacturing process, the grain is converted into beer except
for the omission of hops and is distilled to obtain a distillate containing 80%
alcohol by volume. It is then diluted with water and stored in charred bar¬
rels. After the desired aging period, the whisky is adjusted to required alco¬
hol strength and bottled. The characteristic flavour of scotch whisky is said
to be due to fumes from peat used for firing malt kilns and the characteris¬
tics of the water used.
Brandy can be made from any fruit. Generally, brandy refers only to
distillate from grape wine. Grape wine obtained from selected grapes is com¬
pletely fermented using pure cultures of yeast and distilled. The brandy
obtained is stored in oak casks and is allowed to age in a damp storage
building for as long as 20 years.
Rum is an alcoholic beverage distilled directly from fermented sugarcane
products, such as sugarcane juice, syrup of molasses. The rum obtained by
distillation is stored in either charred, plain or reused barrels or vats. Rum
readily improves in characters and flavour with aging. After aging, the
strength of alcohols is adjusted to 40% and bottled.
Gin is produced by diluting neutral spirit with distilled water so that the
alcohol content is 60%. This is distilled in a pot still in the head of which are
placed juniper berries and other aromatics. During distillation, the alcohol
water vapour extracts the flavouring principles. The distillate is then reduced
to the required alcohol strength by the addition of water and bottled. No
aging is required for gin; in fact, it may be harmful as the essential oils in
gin may decompose with time.
Vodka is a distilled liquor without any identifying characteristics except
that of dilute alcohol. It is free from all traces of colour and flavour. Vodka is
made by diluting neutral spirit obtained from wheat or other cereal grains
or potato.
For preparation of gin and vodka, and for fortification of any other bev¬
erage with alcohol, a colourless and tasteless spirit is required and this can
be obtained by distillation in a continuous still. Dilute alcohol from any
source when distilled in a continuous still can give 95% alcohol. Such alcohol
is very pure and has only the odour and flavour characteristic of alcohol.
Such alcohol is known as neutral spirit (silent spirit).
Liquors are products obtained by steeping herbs, fruits, flowers or plants
in neutral or distilled spirits and distilling the resulting produce. To the
distillate, sugar is added up to 2.5%. As a rule, liquors are sweet, and cara-

238
 BEVERAGES

mel colour or other colouring may be added. Liquors like Benedictine.

Drambuie, Creme-de-menthe are obtained this way. The recipes of most
liquors are closely guarded secrets.

Traditional eastern alcoholic beverages

Toddy is the sap from palm and other trees which has undergone alco¬
holic fermentation. The method of tapping the sap differs depending on tree
species. In coconut palm, the lower portion of unopened spadex is bound by
a strong cord, and the uncovered portion is pounded with a mallet; the sap
that oozes out from the prepared tip is collected in pots tied to it.
Chang is a traditional alcoholic beverage from the North-Western part
of India. Cooked rice and other cereals are used as the substrate, called
grim, and the inoculum, called phab, is prepared from herbs. The inocu¬
lated material is fermented under defined conditions. The extract obtained
after fermentation is called chang. Rice beer, shonti annum and other simi¬
lar beverages are prepared from rice, wheat and huskless barley in different
parts of the country, and are called by different names.
Kaomak and takju are traditional alcoholic beverages from Thailand.
Kaomak is prepared from boiled glutinuous rice with spices. Takju is pre¬
pared from barley, corn and wheat.
Feni is a traditional distilled alcoholic beverage of India prepared from
cashew apple in Goa. The juice is fermented, and distillation is carried out
in 2 stages. The distillate of coconut toddy is called coconut feni
Country liquor is prepared from such raw materials as jaggery, potato,
fruits like orange and mango, etc., spices like cardamom, aniseeds, coriander
and ginger, and flower like rose and jasmine, are also used for distinctive
perfuming. Modhuka is another alcoholic beverage prepared from mahua
flowers.
The main types of alcoholic drink and their calorie values are given
below (Brian and Allen, 1970).

Type Alcohol content Calorie value (cal/100 ml)

Beer
Bitter 3 30
Mild 3 25
Cidey
Dry 4 35
Sweet 4 40
Wine
White 9 70
Red 9 65
Fortified 16 135
Spirit
Whisky 31 220
Liquor
Benedictine 39 270

-1
239
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

The salient features of traditional methods area:

(z) Use of microorganisms to modify the substrate and release
fermentable sugars
(u) Use of starter cultures prepared under specific conditions, some¬
times using natural plant materials.
(zzz) Absence of rigid temperature control.
(iv) Fermentation normally by mixed flora.
(v) Absence of any stringent precautions during fermentation
or processing to avoid cross-infection. In contrast, modern conven¬
tional fermentations include highly rigid controls and demanding
conditions of fermentation and processing.
Traditional alcoholic beverage may be relevant to developing countries
on grounds of cost, technology, and availability of infrastructure and raw
materials.

REFERENCES

Amerine, M.A. 1972. Quality control in the California wine industry. Journal of Milk Food
Technology 35: 373-378.
Amerine, M.A., Berg, H.W. and Cruess W.V. 1972. Technology of Wine Making. Edn 3. AVI
Publishing Co., Inc. Westport, Connecticut.
Alok, J., Mann, R.S. and Balachandran, R. 1996. Tea: A refreshing beverage. Indian Food
Industry 15(2): 22-28.
Brian, A.F. and Allon, G.C. 1970. Food Science—A Chemical Approach. University of London
Press Ltd, St. Pauls, Warwick Lane, London.
Broderick, H.M. 1977. The Practical Brewer. A Manual for the Brewing Industry. Edn 2. Master
Brewery Association of the Americans, Madison, Wisconsin, USA.
CSIR, New Delhi. 1950. Wealth of India, Vol II. Council of Scientific and Industrial Research,
New Delhi, 299 pp.
Cruess, W.V. 1947. The Principles and Practice of Making. AVI Publishing Co., Inc., Westport,
Connecticut.
Frazier, W.C. and Westhott, D.C. 1995. Food Microbiology. Edn. 4. Tata McGraw-Hill Publish¬
ing Co. Ltd, New Delhi.
Hardwick, W.A. 1973. Recent Advances in Brewing Technology, (in) Fermented Foods. Proceed¬
ings of Eighth Annual Symposium. N. Y. State Agricultural Experiment Station Special Re¬
port, 16 April 1974.
Joe, A.M. and Shahani, K.M. 1975. Grapes and wine technology: grapes to wine. Journal of
Milk Food Technology 38: 237-243.
Rice, A.C. 1973. Yeast fermentation in wine technology. Proceedings of Eighth Annual Sympo¬
sium, N.Y. State Agricultural Experiment Station Special Report, 16 April 1974.
Shakunthala, M. N. and Shadaksharaswamy, M. 1987. Foods: Facts and Principles. Wiley
Eastern Limited, New Delhi.

LEARNER’S EXERCISE

1. What care is required in preserving the flavour of coffee in processing and preparation
stages?
2. How are beverages classified? List their functions.
3. What are the different stimulating beverages? Name the stimulant in these beverages.
4. Write in detail about the processing and preparation of any two beverages.

240
 Condiments
and spices

I ndia is considered to be the home of spices. Even before the Christian era,
traders and explorers from various parts of the world came to India to
exchange their valuable merchandize for Indian spices.
A diet composed of just the nutritive components may be quite insipid.
To be palatable it should have flavour. In other words, man does not live by
bread alone! The spice of his food life is concerned with what goes with his
bread. According to the International Organization for Standardization, there
is no clear-cut division between spices and condiments and so they are
clubbed together. The term spice or condiment applies to such natural plant
or vegetable products or mixtures thereof, in whole or ground form, as are
used for imparting flavour, aroma and pungency to and for seasoning food.
There are about 70 spices grown in different parts of the world. Many of
them are grown in India. Spices can be classified in different ways, such as,
according to their botanical families, economic importance, method of culti¬
vation or part of component of the plant, such as seeds, leaves, bark, etc.
Each system has its own merits and demerits. A method of classification
depending on the origin and active principles present in spices (Shakuntala
and Shadaksharaswamy, 1987) is as follows:

1. Pungent spices: Pepper, ginger, chillies, mustard

2. Aromatic fruits: Cardamom, nutmeg and mace, fenugreek, anise,
fennel, caraway, dill, celery, cumin, coriander etc.
3. Aromatic barks: Cinnamon, cassia
4. Phenolic spices containing eugenol: Cloves, allspice (pimento)
5. Coloured spices: Paprika, saffron, turmeric

Spices are mostly used as flavouring agents in a number of food stuffs,

such as curries, bakery products, pickles, processed meats, beverages, liq¬
uors etc. They enhance or vary the flavours of foods. Spices are also flavour
disguisers. They help mask the off-flavour of foods which, if unspiced, have
to be thrown away. Some spices posses antioxidant properties while others
are used as preservatives in some foods like pickles and chutney. Others,
like cloves and mustard, possess strong antimicrobial properties and, as
such, prevent food spoilage. Spices were used to preserve meat for long
periods when there was no refrigeration. Many spices also possess impor¬
tant physiological and medicinal properties.

241
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Composition
Spices are obtained from a large number of different plants. They are
parts of plants, such as roots, buds, flowers, fruits, barks or seeds. Most
spices owe their flavouring properties to volatile oils, and in some cases, to
fixed oils and small amounts of resins, which are known as oleoresins. In
many cases, no single compound is responsible for flavours; a blend of dif¬
ferent components, such as alcohols, phenols, esters, terpenes, organic ac¬
ids, resins, alkaloids and sulphur-containing compounds contribute to the
flavour. In addition to flavour-contributing components, all spices contain
usual components of plant products, such as proteins, carbohydrates, fi¬
bres, minerals and tannins or polyphenols.

Flavouring extracts
Spices, being agricultural commodities, are prone to spoilage by insects
or microbial attack. Hence the spice oils or oleoresins which contain all the
active principles of spices are extracted and marketed. Spice oils are ob¬
tained by the steam distillation of ground spices. Oleoresins are obtained by
solvent extraction of ground spices or more advantageously, the steam dis¬
tilled spice. The spice oils contain only aromatic principles, while the
oleoresins contain both the aromatic and pungent principles. Various sol¬
vents like acetone, isopropanol, methanol, hexane, etc. are used as sol¬
vents. According to BIS Standards, oleoresins obtained from solvent extraction
should not contain more than a specified amount of solvent. The processed
products of spices have several advantages—they are convenient to use,
free from contamination, have better storage life and are easy to transport.
Technology has developed in India to prepare ready-to-use oleoresins from
spices (Shakuntala and Shadaksharaswamy, 1987).
The list of spices along with the common and botanical name used as
under the purview of Spices Board, India, are given in Table 29 (Spices
Board, India, 1994).

Table 29. List of spices (under the purview of the Spices Board, India, 1994)

English name Botanical name Family Part used

1 2 3 4

1. Cardamom (small) Elettaria cardamomum Zingiberaceae Fruit seed

Cardamom (large) Amomum subulatum Zingiberaceae Fruit seed
2. Pepper Piper nigrum Piperaceae Fruit seed
3. Chilli, bird chilli Capsicum frutescens Solanaceae Fruit seed
Capsicum Capsicum annuum Solanaceae Fruit seed
Chilli Capsicum annuum Solanaceae Fruit seed
Paprika Capsicum annuum Solanaceae Fruit seed
4. Ginger Zingiber officinale Zingiberaceae Rhizome
5. Turmeric Curcuma longa Zingiberaceae Rhizome
6. Coriander Coriandrum sativum Umbelliferae Leaf and seed

242
 CONDIMENTS AND SPICES
(Table 29. concluded)

1 2 3 4

7. Cumin Cuminum cyminum Umbelliferae Fruit

8. Fennel Foenicutum vulgare Umbelliferae Fruit
9 Fenugreek Trigonella foenum- Fabaceae Seed
graecum
10. Celery Apium graveoiens Umbelliferae Fruit
11 Aniseed Pimpineila anisum Umbelliferae Fruit
12. Bishop’s weed or Trachyspermum ammi Umbelliferae Fruit
carum
13. Caraway Carum carvi Umbelliferae Fruit
14. Dill Anethum graveoiens Umbelliferae Fruit and seed
15. Cinnamon Cinnamomum verum Lauraceae Bark
16. Cassia Cinnamomum aromaticum Lauraceae Bark
17. Garlic Allium sativum Alliaceae Bulb
18. Curry leaf Murraya koenigii Rutaceae Leaf
19 Kokam Garcinia indica Clusiaceae Peel of fruit
20. Peppermint Mentha piperita Lamiaceae Leaf
21. Indian mustard Brassica juncea Brassicaceae Seed
22. Parsley Petroselinum crispum Apiaceae Seed
23. Pomegranate Punica granatum Punicaceae Seed
24. Saffron Crocus sativus Iridaceae Stigma
25. Vanilla Vanilla planifolia Orchidaceae Pod
26. Tejpat Cinnamomum tamala Lauraceae Bark and leaf
27. Indian long pepper Piper longum Piperaceae Fruit
28. Star anise lllicium verum Magnoliaceae Fruit
29. Sweet flag Acorus calamus Araceae Fruit
30. Greater galangai Alpinia galanga Zingiberaceae Rhizome
31. Horse-radish Armoracia rusticana Brassicaceae Rhizome
32. Caper Capparis spinosa Capparidaceae Fruit/root
33. Clove Syzygium aromaticum Myrtaceae Unopened flower bud
34. Asafoetida Ferula asafoetida Apiaceae Oleogum resin from
rhizome and thickened
root
35. Cambodge Garcinia cambogia Clusiaceae Pericarp
36. Hyssop Flyssopus officinalis Lamiaceae Leaf
37. Juniper berry Juniperus communis Cupressaceae Berry
38. Bay leaf Leurus mobilis Lauraceae Leaf
39. Lovage Levisticum officinale Apiaceae Leaf
40. Marjoram Marjorana hortensis Lamiaceae Leaf and flower top
41. Nutmeg Myristica fragrans Myristicaceae Seed
42. Mace Myristica malaparica Myristicaceae Aril of fruit
43. Basil Ocimum basilicum Lamiaceae Leaf
44. Poppy seed Papaver somniferum Papaveraceae Seed
45. Allspice Pimenta dioica Myrtaceae Fruit and seed
46. Rosemary Rosmarinus officinalis Lamiaceae Leaf
47. Sage Salvia officinalis Lamiaceae Leaf
48. Savory Satureja hortensis Lamiaceae Stem, leaf, flowering top
and seed
49. Thyme Thymus vulgaris Lamiaceae Leaf and flowering top
50. Marjorum Origanum vulgare Lamiaceae Leaf and flowering top
51. Tarragon Artemisia dracunculus Asteraceae Leaf
52. Tamarind Tamarindus indica Caesalpiniaceae Fruit

243
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Spices are listed alphabetically. Common names of spices, condiments

and herbs, and a couple of their Indian names are also given. Chief con¬
stituents (abbreviated to CC) that confer on their distinctive flavour and
taste. Most of these commodities are familiar Indian products, but a few
that are imported for use in manufactured foods, or in the home kitchen to
create exotic dishes are also included (Balasubramanyam, 1985).
Allspice or pimenta (seetul, gandamenasu, kattukuruva)
Round, reddish-brown unripe berries that are dried and sometimes
ground. Name derived from its mixed flavour of cloves, cinnamon, nutmeg
and black pepper. Ingredient of curry powders, pickling powders, mince¬
meat spice. CC: eugenol.
Aniseed (vilayati saunf, shonibu)
Seed obtained by simply drying the whole fruit. Strongly resembles true
Indian saunf or fennel. Mostly imported from Europe. CC: anethole.
Arecanut (supari, adekke, pakku)
Nuts of a palm, which may be used after simple halving and drying. To
improve colour, taste and keeping quality, the excess of tannins and muci¬
lage is removed, the nuts are frequently cured by boiling the whole nut, or
halves, or slivers, in an extract from the previous year’s operation. Betal
nuts are chewed as such, after scenting, sweetening and blending with sugar,
copra and other spices, or along with betel leaves and slaked lime. Kattha,
which is also smeared on betal leaves, is a tannin-rich material derived
from the heartwood of the same tree. CC: catechin (astringent), arecolin
(stimulant).
Asafoetida (king, perungayam)
Root exudate, collected and formed into ‘tears’ (balls), mass or paste. In
commerce, hing is the light-coloured, water-soluble, less aromatic product,
while hingra is the darker, oil-soluble, more aromatic product derived from
a different variety of tree. Mostly imported from Iran and Afghanistan. CC:
mixed alkyl disulphides.
Bay leaf
Leaf, used fresh. CC: linalool, methyl cinnamate.
Betal (paan, tambula, vettilai)
Green leaves of a creeping vine, belonging to the pepper family, which
grows all over India. The leaves are of various sizes, shapes, shades of green
and degrees of pungency. They are chewed after a meal to stimulate the
digestion, usually after being smeared with slaked lime and kattha pastes,
and folded over arecanut grits. CC: eugenol.
Bishop’s weed (ajowan, omum)
Both seed (the dried greyish-brown fruit) and fresh leaf are used. CC:
thymol.
Caper (kabra, mullukatari)
Flower buds of a trailing European shrub. Used green, or pickled in
vinegar, to flavour mutton and fish. CC: rutic acid.

244
 CONDIMENTS AND SPICES

Caraway (shia jeera, seemai shembu)

Seeds, obtained by drying whole plant and then threshing. Smaller than
jeera. CC: carvone.
Cardamom (choti elaichi, yelakki)
Fruit capsule. Grows on long spikes that take off underground from the
stem, and shoot straight out of the ground. Nearly ripe fruits are dried with
hot air to a dark green colour. White cardamoms are obtained by bleaching
with burning sulphur (dioxide) fumes or bleaching powder. CC: cineol,
borneol, camphor.
Celery [ajmoda, shalari)
Ripe fruit of the same plant that carries salad leaves. Fruit is dried to
small seeds, also used as bird feed. CC: limonene.
Chillies and capsicum (mirch, molaga)
Fruits of several varieties of the family solanaceae that yield pungent
red chillies, pungent green chillies and mild (sweet) bell peppers. Vary in
colour (red, green, yellow, white), length (from 1 to 30 cm) and shape (long,
thin, round, oblong). All chillies originated in the Americas, and were spread
to the rest of the world following Columbus. Introduced into India by the
Portuguese, popularized in the 17th century. Used green or dried. CC:
capsaicin, a pungent compound present in amounts varying from traces to
2% in all chillies.
Chillies paprika or Spanish pimento (hardly cultivated in India)
Belongs to the mild Capsicum annuum group. Fruits red, medium to
small, quite fleshy. Introduced into Hungary through a Turkish invasion,
and hence called Turkish pepper or pimenton. Bred in Europe to a low
pungency and a brilliant red colour, but now also grown in California. Never
used as a whole, but only as powders that come in a range of colours and
flavours from various countries.
Chillies cayenne or tabasco or bird
Varieties of Capsicum frutescens. Small, conical, very pungent fruits,
dried under the sun or mechanically. Used to make tabasco sauce and Chi¬
nese chilly sauce.
Cinnamon bark (dalchinilavang patti)
Bark of several species of true cinnamon and cassia trees. Gutter-shaped
pieces are cut from larger trees, and smaller quills (rolls) from smaller trees.
Washed, dried and sometimes fermented for two days. Also powdered. CC:
cinnamaldehyde.
Cinnamon leaves (tejpat, talisapatri)
Obtained from a species of cinnamon tree. Sun-dried, then packed in
bundles. CC: eugenol.
Clove (lavang)
Unopened flower bud of a tree 10 m tall. Picked green, sun-dried to a
dark colour. Name derived from its resemblance to a nail (French, clou).
Pale brown or whitish cloves result from undesirable fermentation. CC: free

245
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

engenol (80%) and engenol acetate in the bud button, and more of the ac¬
etate in the stem; however the odour is not due to these but to other trace
constituents.
Coriander leaf (kothmir)
Entire tender plant is aromatic. CC (of flavour): decylaldehyde.
Coriander seeds (dhaniya)
Seeds lightly roasted, often powdered and used. Name derived Irom the
Greek koris, meaning bug. CC (of flavour): decylaldehyde.
Cumin, white (jeera)
Fruits dried to yellow-to-greyish brown seeds. Flowers of plant are white
or pink. CC: cinnamaldehyde.
Cumin, black (kala jeera, kalunji)
Seeds of a plant species different from true jeera, with pale blue flowers.
Not common in India. CC: carvone, limonene.
Curry leaf (kari paiha, harsanga)
Leaves, used fresh or lightly-dried. CC: sabinene, pinene, dipentene.
Dill (sowa, surva, sabasige)
Dried ripe seeds. Indian dill is from the same plant family as European
dill seeds, but from a different species, with broader and shorter seeds. CC:
dillapiole, carvone, phellandrene. European dill seed has no dill-apiole and
twice the carvone content.
Fennel (saunf\ shombei)
Dried ripe-fruit seeds. Sometimes confused with aniseed (vilayatisaunfi.
Flavour depends on the plant sub-species and climate in which grown. CC:
anethole.
Fenugreek (methi, venthiyam)
Dried ripe pod carrying 10 to 20 small, hard, oblong seeds. CC: carries
practically no volatile material, but does contain a bitter alkaloid, and also
trigonelline, which on heating is converted into the vitamin, niacin.
Garlic (lassan, vellaipundu)
White underground bulbs, lifted and cured for a few days under the
shade. Consist of sectional ‘cloves’. CC: dialkyl disulphides and trisulphides,
derived by hydrolysis of allicin, the major odour pinciple.
Ginger \adrak, inji)
Rhizome (root), used either green (sunti) or sun-dried (adrak), either
peeled or unpeeled. Contains both aromatic volatile oils (CC: camphene,
zingiberene) and pungent non-volatile constituents (CC: zingerone).
Kokam (murgala, kachampuli)
Globular fruits (3 cm) with 6 large seeds. Used as an acidulant, either
as such, or by soaking the outer rind repeatedly in the juices of the pulp,
and then sundrying the mix. Seeds contain a fat (kokam butter), used as an
emollient and as a hard fat in soap making and confectionery. CC:
hydroxycitric acid (sour).

246
 CONDIMENTS AND SPICES

Mace (javatri, jaiphal)

Scarlet aril that envelops the black seed shell of the mace fruit, and
becomes visible when the ripe fruit bursts open. The aril is carefully pried
away and pressed flat and thereafter dried to give a red-brown, translucent,
brittle material, which is cut into the strips of commerce. Flavour resembles
that of the nutmeg, but is more refined. CC: pinene, camphene.
Mango, green (amchur, manga podi)
Sun-dried slices or powder of unripe fallen mangoes of many varieties.
Keeps for a year or so in airtight bottles. Used as a souring agent in Indian
cooking. CC: malic acid.
Mango-ginger (aam haldi, mangai inji)
Neither mango nor ginger, but the dried rhizomes of a plant of the tur¬
meric family. Flavour lacks the pungency of ginger, but resembles that of
raw mango. CC: ocimene, myrcene, limonene.
Marjoram (marwa, marugu)
Dried grey-green leaves with or without the flowering tops. Often used
in flower garlands and venis, and in Western-style cooking. CC: carvacrol,
linalool.
Mint (pudina, muthina)
Fresh leaves. Used to make chutneys and sauces. There are at least 40
species of Mentha, of which three are important in India, and this includes
a variety imported from Japan. Peppermint oil, obtained from mint, is usu¬
ally used after crystallizing away half the menthol. CC: menthol, menthyl
acetate and menthone.
Mustard (rai, sarson)
A small, round, reddish-brown or purple-black oilseed, four varieties of
which are common; yellow sarson, brown sarson, toria and rai The brown
varieties are used extensively in Indian cooking, and the yellow and brown
varieties as a source of a pungent cooking oil popular in Bengal and Punjab.
Two varieties, Banarsi rai and safed rai, which are particularly pungent, are
ground with water to give Western-style table mustard pastes. The pungency
is the result of an enzyme action, and must be developed by slowly grinding
the seeds with water. Roasting the seeds or frying them, as in Indian cooking
practice, destroys the enzyme and suppresses pungency. CC: various
thioglucosides which are enzyme-hydrolysed to several pungent alkyl
isothiocyanates.
Nutmeg (jaiphal, jajikai)
Peach-like fruit dried down to the kernel. Greyish-brown with white
furrows. Mace or javatri is the aril of the same fruit, usually removed before
the nutmeg is dried. CC: myristicin, geraniol, pinene, camphene.
Onion (piyaz, irulli)
Bulb, partly dried but still succulent, from red to white in colour. Ex¬
tensively used in cooking, or raw as a salad, or for pickling. The pungency of
an onion is developed only when it is cut, by enzyme action on a flavourless

247
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

precursor. Boiling or shallow frying in oil makes the product translucent

through starch gelatinization, and destroys the pungency both by killing
the enzyme and volatilizing the acrid constituents. Further frying causes
browning, and a sweet taste develops by caramelization. CC: alkyl disulphide.
Oreganum (sathra, miranjosh)
Dried, light green leaves and tops. Not common in India. An essential
flavouring constituent of many Mexican foods like chilli con carne, and the
tamale and taco. Resembles marjoram, sage and thyme in flavour. CC:
thymol, carvacrol, terpenes.
Paprika
See chillies, paprika.
Parsley (ajmud, kothambelari)
Leaves, fresh or dried, and seeds. Mainly a temperate crop. The greens
constitute a delicate garnish resembling coriander. The seeds carry a fatty
oil of disagreeable flavour and odour. CC: apiole, alpha-pinene.
Pepper, black (kali mirch, kara menasu)
Sun-dried, unripe berry growing on the spikes of a climbing vine. Fully-
mature but unripe, greenish-yellow berries on drying yield black or brown
pepper: ripe orange-red berries yield white pepper if the skin is removed,
either before or after the drying operation, by steeping in water or steaming.
Both forms of pepper can be ground. CC: piperine and chavicine, both of
which on hydrolysis with saliva or water yield the pungent piperidine, which
gives pepper its bite. The odour is due to alpha and beta-pinene, phellandrene,
other terpenes.
Pepper, long (pipli, hipli)
Dried fruit of a climbing wild plant. Used as a spice, like pepper, but is
less pungent.
Peppermint (gamathi pudina, vilayati podina)
Leaves of a certain variety of mint, not common in India. Source of
peppermint oil with its strong agreeable odour and ‘cooling’ mouth-feel. CC:
menthol, limonene, menthone.
Pomegranate (anardhana, dalambi)
Dried angular seeds (fruit globules) especially from a wild variety called
darn. Used in the form of grits or powder as a souring agent in north Indian
cooking. CC: oxalic acid.
Poppy (khuskhus, gasalu)
Tiny seed of the opium poppy. Used in Indian cooking for its nutty
flavour and crunchy texture. Carries no morphine narcotics, except through
contamination with paritcles of the capsules in which the seeds are housed.
Saffron (zafran, kesari, kunkuma)
Dried,light, deep-orange, strongly-flavoured stigmas of a crocus flower
of lavender colour that grows in Kashmir. After sun-drying, the stigmas are
sorted by hand to give the best whole grade (shafrz); this is followed by float-

248
 CONDIMENTS AND SPICES

ing the rest in water twice, each time collecting the heavier particles (mogra,
laccha). CC: picrocrocin (bitter taste) and crocin (orange colour).
Sage [sefakuss, salvia)
Dried grey-green leaf of a variety of salvia. Hardly known in India, but is
widely used in Southern Europe to flavour meat and cheese dishes. CC;
thujone, linalyl acetate, camphor; tannin (astringent component); picrosalvin
(bitter taste).
Spearmint (pahadi pudina)
Leaves of a mint variety, without the ‘cool’ mouth-feel of peppermint.
Not common in India. CC: carvone, terpenes.
Tamarind (imli, puli)
Ripe, dark-brown, fibrous pod-fruit, used fresh, or after drying and
deseeding. Widely used as an acidulant, especially in south India. CC: tar¬
taric acid, glucose, fructose, pectin.
Tarragon or Estragon
Dried leaves and tops, with an odour resembling aniseed. Not grown in
India. Used to flavour vinegar, pickles, mustard. CC: methyl chavicol,
phellandrene, ocimene.
Thyme (banajwain, marizha)
Dried leaves and flowering tops, brownish-green. Grows only at high
altitudes in India, but is common in the western world. Used to season
tomato soups, clam chowder, poultry meat. CC: thymol.
Turmeric (haldi, manjalj
Dried, boiled and polished rhizome (swollen underground stem). Exten¬
sively used as fingers or powder in Indian cooking for its flavour and colour,
and in religious ritual (orange being a sacred colour), cosmetics (as a hair-
remover, and to make kumkum or sindhoor) and medicine. CC: curcumin
(colour), zingiberene, other ketonic sesquiterpenes, borneol (flavour).
Vanilla (vanilla)
Cured fruit-pods of a climbing variety of orchid. The Malagasy Republic
(formerly called Madagascar) grows three-quarters of the world crop; little is
raised in India. During fermentation curing, the vanilla odour develops by
hydrolysis of a sugar-vanillin precursor. Widely used to flavour ice-cream,
chocolate and many sweet foods. CC: methyl vanillin; both methyl and ethyl
vanillin are made synthetically.

Nutritive value
Since spices, condiments and herbs are consumed in very small quan¬
tities everyday, their contribution by way of the macro elements of nutri¬
tion, viz. carbohydrates, proteins and fats, cannot obviously be of any
significance. Occasionally, however, an exceptionally high level of a min¬
eral, or even more so of a vitamin, which are the 2 micronutrient groups of
nutrients, could have some meaning in nutrition. This is especially true
where the material is one which is used in fair amount in cooking.

249
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Table 30. Micronutrients in some common Indian spices

Material g/100 g edible material mg/100 g edible material

Calcium Phosphorus Iron Thiamine Riboflavin Niacin Vit. C Vit. A

Onion 0.3 0.29 Trace 0.42 0.06 0.6 14.7 0.05

Garlic 0.1 0.42 0.01 0.68 0.08 0.7 12.0 0.05
Ginger 0.1 0.15 0.01 0.05 0.13 1.9 12.0 0.05
Turmeric 0.2 0.26 0.05 0.09 0.19 4.8 49.8 0.05
Chilly powder 0.1 0.32 0.01 0.59 1.66 14.2 63.7 1.85
Green chilli 0.03 0.08 1.2 0.19 1.18 0.5 111.0 Trace
Red (dried) chilli 0.16 0.37 2.3 0.93 0.43 9.5 50.1 0.18
Mustard seeds 0.3 0.79 0.01 0.65 0.45 8.5 22.1 0.06
Tamarind 0.2 0.11 0.01 Nil 0.07 0.7 3.0 0.03
Curry leaf 0.8 0.60 0.01 0.08 0.21 2.3 4.0 3.78
Dhaniya 0.8 0.44 0.01 0.26 0.23 3.2 12.0 0.05
(coriander seed)
Jeera 0.9 0.45 0.05 0.73 0.38 2.5 17.0 0.05
(cumin seed)
Adult daily 0.5 (0.5) 0.024 1.4 1.7 19.0 40.0 0.75
requirement

Table 30 shows some micronutrient minerals and vitamins present in

spice materials, listed roughly in decreasing order of their use in an Indian
kitchen. Calcium is high in Jeera, dhaniya and curry leaves, and iron in
green chillies and dried red chillies (Spice Board, 1994). Phosphorus is present
in good amounts in mustard seeds, and curry leaves, but many other spices
(dhaniya, jeera, garlic, red chillies, chilli powder, onion and turmeric) carry
sizeable quantities. In case of vitamins, thiamine occurs in chillies and their
powders, mustard seeds, onion and garlic; riboflavin in chilli products and
mustard seeds; and niacin in chilli powder, mustard seeds and turmeric
powder. Rich sources of vitamin C are green chillies, dried red chillies, chilli
powder, and turmeric powder, while curry leaves and chilli powder are good
sources of vitamin A. Thus use of these materials in everyday cooking in
reasonable amounts cannot but contribute cumulatively towards the needs
of vitamins and minerals of the human body.
The antimicrobial or antiseptic properties of many spices are well docu¬
mented experimentally. Allicin, present in garlic, has a killing action against
a very wide range of bacteria, and markedly reduces the actual bacterial
load in experimental animals. It is also active against fungi. Curcumin, the
yellow colouring matter of turmeric (haldi), has likewise a powerful antibac¬
terial action, and asafoetida destroys coliforms and anaerobes in the caecum.
Similarly the suppressive power of many other spice oils has been proved,
such as those of ajowan, aniseed (saunj), asafoetida (king), clove, cinnamon,
onion and pepper (even against dangerous organisms of the E. coli group).
In the body, such antibacterial action could help to reduce to the flora in the
large intestine, thus reducing gas formation there. Another desirable conse-

250
 CONDIMENTS AND SPICES

quence is the selective stimulation of acid-forming Lactobacillus species, an

effect known to occur when curds are consumed (Achaya, 1986).
The antiseptic properties of spices also lend them a preservative value
when used in foods. Mustard seed and mustard oil perform in this way in
Indian pickles, and cloves and cinnamon in murabbas and fruit preserves.
The preservative action of pepper in meat storage is historical knowledge.
The curcumin of turmeric is an antioxidant that can prevent the food going
bad by oxidative spoilage, a very common occurrence if an oil is present. So
does a material present in betel leaf called chavicol. Spoilage microbes are
more easily destroyed in an acidic environment, and the various souring
agents used in foods, like tamarind, amchur, kokam and anardhana, could
assist in this way. Kokam has actually been shown to extend remarkably
the keeping quality of fresh fish, and garlic that of pork.

REFERENCES

Achaya, K.T. 1986. Everyday Indian Processed Foods, pp. 78-88. National Book Trust, New
Delhi.
Balasubramaniam, N. 1985. Simple home remedies. WISDOM International, pp. 35-37. Govinda
Rao, K.V (Editor).
Shakunthala, M. N. and Shadaksharaswamy, M. 1987. Foods: Facts and Principles, pp. 322-34.
Wiley Eastern Ltd, New Delhi.
Spices Board of India. 1994. Ministry of Commerce, Government of India, Cochin.

LEARNER’S EXERCISE

1. What are the various uses of spices and condiments?

2. How do condiments and spices enrich the food preparation in general?

251
 Miscellaneous foods—
sugar, jaggery and cocoa butter

T he art of making sugar (sucrose) from sugarcane had its birth in India.
Early Indian scripts refer to gur (jaggery) as an article of food. From
India, the making of sugar spread to East to Malaya and China and West to
Persia and beyond. India is the world’s largest producer of sugar and
sugarcane with 276.3 million tonnes in 1997-98. The Union Government
had set a target to produce 300 million tonnes of sugarcane (Indian Agricul¬
ture, 1999). Sugar is a Rs 20,000 crore industry in India. India had even
earlier been the largest producer of sweetening agents out of sugarcane,
when we take into consideration jaggery and khandsari (open pan sugar)
produced in unorganized sector of industry. However, the per caput annual
consumption of gur and sugar in the country is about 24 kg compared with
40-70 kg of refined sugar in developed countries. (Indian Agriculture, 1999).
Sugarcane is the chief source of sugar. Sugarcane belongs to genus
Saccharum. It was recognized in the 19th century that sugarbeet (Beta
vulgaris) is also a rich source of sugar. From the beginning of 20th century,
sugarbeet has become an important source of sugar. In beet, sugar is'stored
in the roots as distinguished from sugarcane where the sugar is stored in
the stem. While sugarcane is grown in tropics, sugarbeet is a crop of the
temperate zones. Sugary substances are also obtained from palmyra, date
palm, coconut, sago palm, maple etc.

MANUFACTURING OF SUGAR

Sugar from cane

Sugarcane contains 12-15% sugars (sucrose, glucose and fructose). In
India, 80-90% of sugarcane is used for the manufacture of 3 products widely
used in food, viz. gur, open pan sugar or khandsari and vacuum pan sugar
or white sugar. The largest quantity, ranging between 50 and 60% of the
cane production, is used for the production of gur, 25-30% for white sugar
and 5% for khandsari. Only a very small quantity of refined sugar is produced
in the country. The balance of about 10% of sugarcane is used for chewing
and sugarcane juice, which is used as a beverage, and as seed and feed. The
cane juice is acidic (pH 5.0-5.4) and in addition to sugars, it contains minerals
(0.4-0.7%) and vitamins. The vitamins present are thiamine 53, riboflavin,
31, niacin 49, pantothemic acid 2.180, biotin 22, and vitamin D 176 pg/
100 g. (Shakunthala and Shadaksharaswamy, 1987).

252
 MISCELLANEOUS FOODS—SUGAR, JAGGERY AND COCOA BUTTER

Raw sugar
In India, sugar from sugarcane is obtained in 3 forms, i.e. raw sugar,
refined sugar and white sugar.
Raw sugar is made by crushing the sugarcane and extracting the juice
by pressure. The juice from the mills is dark green, turbid and acidic (pH
5.0-5.4). The sucrose content varies from 10-18%. The juice is strained
through fine screens to remove particles of fibre and suspended matter.
Then sufficient milk of lime is added to neutralize the acids present and
heated to the boiling point. The lime and heat treatment cause coagulation
of colloidal substances (mud or scum). The hot juice is then run into clarifi¬
ers for sedimentation of mud and decantation of the clear juice. The clari¬
fied juice which is yellow to brown contains 85% water which is evaporated
in multiple effect evaporators to a syrup containing 75-85% sucrose. Sugar
is crystallized from the syrup in single-effect vacuum pans. The crystals are
separated from massecuite (mixture of crystals and mother liquor or molas¬
ses) by centrifugation (Fig. 36).

Fig. 36. Manufacture of raw cane sugar

The raw sugar so obtained consists of brown crystals with an adhering

film of molasses. It contains 96-97% sucrose, 0.75-1.00% reducing sugar
and 0.5-0.75% of moisture; the remaining being organic nonsugars.

253
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Refined sugar
In refining, raw sugar is dissolved in water and the solution filtered
through animal charcoal which adsorbs the colouring matter and some other
impurities. The decolourized solution is then evaporated in multiple-effect
vacuum pans as in the case of raw sugar production, until the sugar crystal-
izes. The massecuite is separated into crystals and syrup and the crystals are
dried in revolving drums or granulators, through which a hot current of air
is drawn. In the case of refined sugar, the size of the crystals is important and
the crystals are screened into granulated sugars of different coarseness.

White sugar
In India, most of the sugar manufactured from sugarcane is white or
direct-consumption sugar. In this case, sugar is made from cane syrup di¬
rectly without the intervening step of making raw sugar. The lime-treated
cane juice obtained as in the manufacture of raw sugar is treated with
sulphurdioxide (sulphitation) or carbondioxide (carbonation). The former
process is more commonly used in India. The rest of the process is some¬
thing of a repetition of the raw sugar manufacturing processes. Sulphitation
produces a near white to yellow sugar, whereas the carbonation process
gives a white product comparing favourably with refined sugar. The recov¬
ery of sugar varies from 9.5-11.5% (Fig.37).

Fig. 37. Refining cane sugar

254
 MISCELLANEOUS FOODS—SUGAR, JAGGERY AND COCOA BUTTER

GUR (JAGGERY)

Gur is produced throughout India and forms an important item of Indian

diet. It is mainly obtained from sugarcane. Gur is also obtained from palmyra,
date palm and coconut. In the manufacture of gur, cane is crushed soon
after cutting (within a day) to avoid loss of weight and sugar due to inver¬
sion. For small-scale crushing, iron crushers driven by bullocks, and for
large-scale crushing, power driven crushers are used. Coarse suspended
impurities from the juice are removed by straining and then the juice is
boiled. When the juice is slowly heated up to the boiling temperature, veg¬
etable or chemical clarificants are used to floculate colloids present in the
juice. After clarification, the cane juice is boiled vigorously to 115°-117°C
(striking point) with the constant stirring, and then concentrated into a
thick almost semisolid mass which, on cooling, solidifies into gur. Special
types of gur are manufactured by decolourizing clarified cane juice by the
use of sodium hydrosulphite or activated carbon obtained from rice husk.
Gur is produced in different forms, viz. as lumps of various sizes and shapes
(Rajyalakshmi, 1974).
Generally, good quality gur has a light colour, good flavour, hardness,
crystalline structure and good keeping qualities. Gur contains 65-85% su¬
crose, 10-15% invert sugar and 2.5% ash. Gur is an article of food which is
peculiar in Indian diet (Frazier and Westhoff 1978). Because of colour and
flavour, it has special appeal in certain preparations like coconut burfi,
groundnut toffees, holige, etc. It lends itself to forming moulds and since it
does not easily crystallize because of the presence of invert sugar, it is very
much preferred when non-crystalline candies are prepared. It is specially
used when it has to act as binder in the preparation of groundnut and
puffed rice balls and other similar products. It is more pliable than sugar
which forms crystals easily or gets caramelized beyond a certain tempera¬
ture. The temperature to which jaggery syrup is to be heated to get the
necessary consistency for different preparations is given in Table 31. The
consistency is determined in the same way as in the case of sugar syrups
(Raghavendrarao etal, 1989).

Table 31. Consistency of jaggery syrup at various temperatures

Preparation Temperature Consistency Behaviour

(°C) obtained of syrup

Balls: puffed rice, groundnut 110-120 Soft ball Transparent

and gingelly balls
Burfies 120-130 Hard ball Transparent
Caramel 130-140 Brittle ball Transparent
Butterscotch 140-145 Hard and cracking Opaque
Brittle 145-150 Multiple needle like thread Opaque

255
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

KHANDSARI SUGAR

For the manufacture of khandsari sugar (open pan sugar or khandi), the
cane-juice extraction and clarification are done in the same way as in mak¬
ing gur. The clarified juice is boiled quickly to the required consistency. The
crystals that separate are removed by centrifugation and dried. Recovery of
khandsari sugar is about 6.0-7.5% on the weight of the cane, which is
rather low. During 1980-81, 54% of the cane crushed in the country was
used for the production of gur and khandsari sugar.

BEET SUGAR

In the manufacture of beet sugar, most of the methods employed in cane

sugar manufacturer are used. Proceedings of Eighth Annual Symposium, N.Y.
State Agricultural Experiment Station Special Report 16 April 1974. Beet
sugar is produced in a one-stage process from beet to refined sugar, unlike
cane sugar which, in many cases, is produced as raw sugar which is then
refined (Magnus Pyke, 1982).
Sugar present in beet is extracted by membrane diffusion operated on
the counter-current principle, using batch system or a continuous diffuser.
The thin juice obtained from the diffusion process is heavily limed and
carbondioxide is passed. The precipitate formed is quickly filtered off and
carbondioxide is again passed through the clear filtrate to precipitate re¬
sidual lime salts. This is followed by a second filtration, after which the
carbonated juice is treated with sulphurdioxide. The sulphated juice is boiled
to drive off occluded gas and again filtered to remove all precipitate. The
purified thin juice is processed to the refined sugar product in much the
same manner as the process used for making refined sugar from sugarcane.

FORMS OF SUGAR

Various forms of sugar are available for use in food preparations. Some
forms are crystalline solids and others are liquids (syrups). The following
are some of the solid forms, other than gur and khandsari.

Cube sugar
This is granulated sugar moistened with white sugar syrup, moulded
into cubes, and then dried in that shape. The cubes are convenient for
sweetening tea and coffee.

Powdered sugar
Such sugar (icing sugar) is made by pulverizing granulated sugar with
or without the addition of any edible starch. Starch, if added, absorbs mois¬
ture and prevents the caking of the powdered sugar. Powdered sugar is
mostly used in confectionery for dressing cakes, pastries and other bakery
products.

256
 MISCELLANEOUS FOODS—SUGAR, JAGGERY AND COCOA BUTTER

Brown sugar
Brown sugar contains some of the molasses from which the crystals are
separated and some glucose and fructose. Some flavour substances are
present in brown sugar. Because of its pleasing and distinctive flavour, brown
sugar is frequently used in baked products. The darker sugar has more
flavour than a light sugar. Brown sugar forms lumps during storage. To
overcome this difficulty, liquid brown sugar is now available.

Rock sugar
Rock sugar (kallu sakkare) is made by boiling sucrose solution to a
syrup consistency (110°—115°C) and pouring it into big trays. Due to slow
evaporation (takes 3 to 4 days) the sugar syrup forms big slabs with few
lumps on top. This is broken into big pieces and used, generally on festive
occasions.

Diamond sugar
Diamond sugar is a decorative sugar in small rectangular crystals. It is
used with beetle nuts and in other confectionery (Thangam Philip, 1965).

SUGAR COOKERY

Sugar is not a dietary essential but ordinarily forms a part of our diet.
Most people seem to have a craving for sweet foods. Every festive occasion is
celebrated with sweets. The bulk of sugar consumed is used in beverages
such as tea, coffee and milk. Sugar is used for preparations of sweets, fruit
preserves and the like. Sugar is also used as a preservative in the preparation
of jams, jellies and cordials. Toffees, chocolates and other popular candies
are made almost entirely of sugars.
Sugar cooking is a task requiring skill. In cakes, biscuits, etc. the sugar
has to blend homogenously with the flour and fat to form a colloidal product
which do not crystallize. In products such as laddus, the sugar tends to
form crystals on the surface if the syrup is not cooked to the right texture.
Preventing crystallization is a major problem in the refrigerator method of
preparing ice-creams as crystals tend to form when the milk is frozen without
constant agitation. This can be prevented by the addition of whipped cream,
beaten eggs, and re-freezing the frozen product after thorough beating and
aeration. The addition of a small quantity of custard powder and the use of
evaporated or condensed milk also help to prevent crystallization.
Sugar is extensively used in confectionery and other foods. The kind of
use depends on the reactions that it undergoes on heating and hydrolysis.
The essential component contributing to the texture of confectionery is the
sugar crystal. Sugar can be ciystalized in different forms and sizes by varying
factors influencing crystal growth.

Caramelization
Sugar, when heated by itself or in a highly concentrated solution, under-

257
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

goes a change called caramelization. As dry sugar is heated it melts to a col¬

ourless liquid and it soon develops a brown colour, giving a pleasing charac¬
teristic caramel aroma. Caramelization can be halted by the addition of water
when the desired colour and flavour have developed. Sugar breaks down
during caramelization and various organic acids are formed. Carameli-zation
of sugar is useful in the preparation of confectioneries (Swaminathan, 1988).

Hydrolysis
Sugar undergoes hydrolysis with acids or enzyme (invertase) when it is
converted into a mixture of glucose and fructose (invert sugar). Invert sugar
can prevent or help control the degree of sucrose crystallization because
glucose and fructose crystallize more slowly than sucrose and also because
a mixture of invert sugar and sucrose has greater solubility in water than
sucrose. Thus the use of invert sugar in candy preparations can alter these
properties. Invert sugar, apart from limiting the amount of crystallization of
sucrose, encourages the formation of small crystals, and this gives smooth¬
ness to candy. The hygroscopicity of invert sugar helps prevent more chewy
candies from drying out and becoming overtly brittle. Invert sugar is sweeter
than sucrose and thus has an effect on the sweetness of candy.

Crystallization
The way sugar crystallizes from its solution is of great importance in the
preparation of confections and other sugar containing products. Fairly large
quantities of sugar are soluble in water at room temperature and the amount
dissolved increases with temperature. The amount of sugar dissolved in boil¬
ing water is about twice the amount of that dissolved at room temperature in
the same volume of water. When a solution of sugar saturated at the boiling
point of water is cooled, crystals of sugar start forming. The size of the crys¬
tals formed depends on the rate of formation of nuclei about which the crys¬
tals grow and the crystal growth rate around these nuclei. In the preparation
of candies, the size of crystals formed and the speed of crystallization are very
important in achieving the right structure. If the crystal formation is rapid,
the size of the crystals is large as there are only a few nuclei on which the
crystal formation can grow. Confectionery with large crystals has a grainy, al¬
most a sandy feel on the tongue (Thangam Phillips, 1965).

Crystaline and non-crystaline sugar

From boiled sugar solution, 2 types of confectioneries are prepared, viz.
crystalline (e.g. fondant and fudge) and non crystalline (amorphous) (e.g.
toffees and brittles).
The first step in the preparation of crystalline products is to dissolve
sugar in water. In crystalline or cream candy, a smooth textured, soft yet
firm, product is to be obtained. This is possible by the addition of ingredients
to sugar solution which aids in the formation of fine crystals.

258
 MISCELLANEOUS FOODS—SUGAR, JAGGERY AND COCOA BUTTER

Table 32. Temperature of tests for syrups and candies

Product Temperature (°C) Test Description of test

Syrup 110-112 Thread When syrup is dropped from a spoon,

syrup spins a 5 cm thread
Barfi, fondant, fudge 112-115 Soft ball Forms a soft ball when syrup is dropped
into cold water; flattens on removal from
walls
Caramels 118-120 Firm ball Forms a firm ball when syrup is dropped
into cold water; does not flatten on re¬
moval from water
Divinity, laddu, marsh 120-130 Hard ball Forms a hard ball enough to hold its
mellow shape when syrup is dropped into cold
water
Butter scotch, toffees 132-143 Soft crack Forms threads which are hard but not
brittle when syrup is dropped into cold
water
Brittle, glace 150154 Hard crack Forms thread which are brittle when
syrup is dropped
Barley sugar 160 Clear liquid Sugar melts
Caramel 170 Brown liquid Sugar melts and browns

Fondant
The ingredients for fondant are acid (cream of tartar) invert sugar and
glucose or corn syrup. The candy mixture is concentrated by boiling until it
reaches doneness. The doneness of the candy mixture is determined by
measuring the temperature of the boiling solution (113°-114°C). Another
method of measuring doneness in making candies is by dropping a small
portion of boiling syrup into very cold water, allowing the syrup to cool and
evaluating its consistency. The consistency of syrup at different tempera¬
tures is given in Table 32.
In the preparation of fondant, at an appropriate stage, boiled solution is
poured on a smooth flat surface and allowed to cool to 40°C. Then it is
beaten continuously until it becomes a creamy mass. At first, the mixture
becomes cloudy from the air beaten into it and then sets into a stiff mass. A
24 hr ripening period in a lightly covered container softens the crystalline
candy slightly and promotes smoothness.
Fondants are used in confectionery for numerous purposes. They are
used to make mints. In this case, the super-saturated sugar mixture in the
boiling kettle is cooled to about 71°C and flavoured with mint. The mint
quickly solidifies on further cooling. Softened fondant is used in coating
fruit and nut mixtures that are moulded and sliced. Fondants are largely
used as cream centres of chocolate confectionery.
The principles of making fudge do not differ from those of making fondant.

Amorphous non-crystalline confectionery

Crystallization of sugar is prevented either by cooking the solution to a

259
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

high temperature so that the finished product hardens quickly before crystals
have a chance to form, or by adding large amounts of interfering substances,
or a combination of both. Temperatures used for making different confections
vary. The final temperature of syrup for caramels is 118°-120°C. During
cooking, a brown colour develops owing to caramelization of sugar and also
due to reactions of amino groups of milk proteins and reducing sugars,
when milk is one of the ingredients. In preparation of caramels, corn syrup,
fats and concentrated milk products are used as ingredients. Brittles are
made merely by the melting and caramelization of sugar. Toffee is made
from simple sucrose syrup with the addition of cream of tartar, vinegar or
lemon juice. Flavour substances are added when the solution has cooled
sufficiently. Spongy candies like marshmallow and gum drops are made
using gelatin as an ingredient.

CONFECTIONERY AND CHOCOLATE PRODUCTS

The art of making confectionery is an old one. Confectionery is essentially a

sugar-based industry and includes sugar-boiled confectionery (candies or
sweets), chocolate confectionary and traditional Indian sweet meats. It is a
product liked by all, especially children.
The commercial production of confectionery started in the 19th century
and its development has been phenomenal. In advanced countries, confec¬
tionery is produced on a very large scale and the annual per caput con¬
sumption is 20-25 kg, while in India it is just about 0.1 kg.

Confectionery ingredients
A variety of ingredients are employed in the manufacture of candy. The
chief among them are sugar and syrups. Dairy products like butter and
whole milk, condensed, evaporated, skim milk and dried milk are used. The
edible portion of fruits, such as apple, lemon, orange, pineapple etc. and
dried fruits like figs and raisins are also used. Amongst nuts, almond, coco¬
nut, the toasted edible portion of peanuts, pecans and walnuts find use.
Other ingredients used are starch and its derivatives, fats, flavours, colours,
gums, pectin and gelatin. Besides, in chocolate confectioneiy, cocoa products
are used (Shakunthala and Shadaksharaswamy, 1987).

Starch and its derivatives

In the confectionery industry, maize starch powder and its derivatives
like liquid glucose, thin-boiling starch, dextrin, dextrose, sorbitol and malto-
dextrin are being used in large quantities.
Liquid glucose, is obtained by the acid and or enzyme hydrolysis of
starch. The combined acid and enzyme hydrolysis gives a syrup of high
dextrose equivalent and better quality. Liquid glucose is mostly used in
toffee, chocolate, lollipops, chewing gum, bubble gum and chikki. It is used
along with sugar.
260
 MISCELLANEOUS FOODS—SUGAR, JAGGERY AND COCOA BUTTER

Maize starch powder is used in the manufacture of chewing gum, pas¬

tries and panned sweets. Starch derivatives like crystalline dextrose, sorbitol
and malto dextrin are used in confectionery industry because they confer
special characteristics to confectionery, such as prevention of drying, im¬
provement of shelf life, increase of nutritive value, etc.

Confectionery fats
Confectionery fats can be divided into 2 categories, viz. fats for general
and traditional functions and fats associated with chocolate confectionery.
Fats play an important part in providing the desired textural property which
can be adjusted by the amount of fat used and how it is mixed. Fats lubri¬
cate the ingredients, thus improving their overall eating qualities which are
dependent on moisturization and tenderness. Confectionery fats should have
a sharp melting point at approximately body temperature and have an opti¬
mal solid-to-liquid ratio to ensure no waxy or oily mouthfeel of the finished
product.
Cocoa butter is an essential ingredient in the manufacture of choco¬
lates. It contracts on solidification which makes possible the moulding of
chocolate blocks and bars with attractively shaped confections. It exhibits
brittle fracture below 20°C. It has sharp melting point around 30-32°C. The
melting and solid: liquid ratio of cocoa fat gives the finished product excel¬
lent snap property.
Ghee is a traditional confectionery fat. It is easily prone to rancidity and
staleness. Because of its cheapness, vanaspati has almost replaced ghee in
the preparation of confections. Indian confectionery products where the struc¬
ture is furnished by ghee or vanaspati lose their structure, especially during
summer months owing to oil seepage. By appropriate hydrogenation, a fat
of required functional properties should be obtained to overcome this defect.

Colours and flavours in confectionery

In order to achieve attractiveness and variety to confectionery, addition
of colours and flavours becomes necessary. Colours are used to increase the
eye appeal and be suggestive of flavour employed. For example, an orange
colour to match the orange flavour or a yellow colour to match lemon flavour
may be used. Colours should be harmless, readily soluble in water and
should not be affected by action of acid, alkali, temperature and light. Artificial
colour should not be added when the product has a rich natural colour as in
chocolate. Lemon, orange, pink, coffee and chocolate shades are the most
commonly used colours.
There are 2 classes of colours used in confectionery—natural and syn¬
thetic. Natural colours like those obtained from black and purple grapes,
red beet, florets of safflower, rind of ripe fruits and from some insects, as
also turmeric and saffron are useful as colourants. In case of artificial colour,
only the permitted colours are to be used and it is better to use only mild
colours.

261
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

A wide variety of flavours are used in confectionery. They belong to 3

main categories, viz. natural, synthetic and blends. Natural flavours are
prepared from the skins and peels of fruits and from roots etc. Most popular
flavour is vanilla. Other important natural flavours are those of lemon, or¬
ange, coffee and cocoa. Synthetic flavours can be used when the desired
flavours cannot be completely extracted from natural raw materials. To stimu¬
late natural flavour, acids such as citric, tartaric and malic are used. Syn¬
thetic flavours are powerful and should be used with caution. The dosage
should be just sufficient to suggest the desired flavour and should not leave
an intense after-taste in the mouth. There are also flavours prepared by
blending natural and synthetic materials. It is better to use blends rather
than any pure or synthetic flavours.

Gums, pectin and gelatin in confectionery

The softer candies such as gum drops and jellies owe their chewiness in
part to gums, pectin and gelatin. These are valuable as binders, filters,
stabilizers and coatings. Gums used in confectionery are gum arabic and
gum tragacanth, sea weed extracts, such as agar-agar and carrageenan,
are also used. However, these are being replaced by starch and pectin. Gelatin
is used in confectionery industry because of its elastic consistency and its
power of holding air and water. It also inhibits the crystallization or graining
of sugar.

Chocolate confectionery
Chocolate is widely appreciated confectionery. Because of its satisfying
value and high energy, it is manufactured and consumed in large quantities
in the western world. The shelf-life of chocolate, particularly in summer
months, is poor. Chocolate confectionery manufacturing starts with cocoa
mass or bitter chocolate from which plain or sweet chocolate and milk choco¬
late are obtained. In making chocolates, the ingredients—chocolate liquor,
cocoa butter, sugar and milk solids in case of milk chocolates—are sub¬
jected to fine grinding, which results in reduction of size of the sugar crys¬
tals and other ingredients. The product at this stage will be a flaky powder.
This is next conched or kneaded in special heated tanks provided with pres¬
sure rollers that grind and aerate the now melted mass to develop
increased smoothness, viscosity and flavour. Conched liquid chocolate is
tempered by stirring and then cooled to promote controlled crystallization of
cocoa fat. This treatment helps obtain chocolate of uniform texture.
Tempered chocolate is used for making bars and coating candy pieces.
For making bars, the tempered chocolate mass is poured into pre-heated
moulds and cooled. The coating of small and round confections is carried
out by panning, the candies are added into revolving heated pans and molten
chocolate is sprayed into the pan. As the candies gently tumble, they become
uniformly coated with chocolate. Then the pans are chilled with cool air to

262
 MISCELLANEOUS FOODS—SUGAR, JAGGERY AND COCOA BUTTER

solidify the chocolate coating. Chocolate panned items frequently are further
polished and glazed.
Larger candy pieces and those that are not rounded are coated with
molten chocolate by a method known as enrobing. In this case, the candy
centres are first bottomed by passing on a screen over a layer of molten
chocolate. Then they pass through a tunnel in which they are showered by
molten chocolate. The pieces emerging from the tunnel quickly cool, solidi¬
fying the coating.

Indian confectionery
Indian confectionery products (sweet meats) occupy a privileged place
in our social customs, being always associated with happy and gay occa¬
sions. There are many varieties of preparations, each with its own unique
texture, flavour and other sensory attributes.
Classes of Indian confectionery
Indian confection may be broadly classified under 4 groups depending
on the base ingredients used.
(a) Khoa (open pan concentrated milk) based products like burfi, pedas,
gulab jamoon, kalakand, etc.
(b) Channa (acid-precipitated casein) based products, like sandesh,
rosogolla, rasamalai, chamcham, channa kheer, etc.
(c) Flour, sugar and fat based products like sohal haliva, shonepapadi,
mysorepak, laddoo, boondi, jalebi, etc.
(d) Others like walnut burfi and other nut candies, sajappa, shrikhand,
etc.
The physical forms of Indian sweet meats vary. Products like mysore
pak, sandesh, barfi and peda are solid; kalakand and rabbi are semisolid;
and rosogolla and jamon are balls of protein-starch with the interstitial spaces
filled with sugar syrup.
Sweet meats show a wide variation in to moisture content. Some have
less than 3% moisture (mysore pak, shone papadi), some have 10-20%
(pedha, barfi, jalebi, etc.), others have more than 20% moisture (rasogolla,
shrikhand). Similarly, they vary in their fat content. Those containing up to
5% fat are shrikhand and rosogolla, about 20% are barfi, cashew, burfi,
sandesh, etc. and 25% and above are mysore pak, shone papadi, etc. The
sugar content of Indian sweet meat is invariably high, lying between 35 and
55%.
The shelf life of Indian confectioneries is poor. Those with a moisture
content of about 15% have a shelf life of only 2-5 days. Storage results in
loss of flavour, staleness, rancidity, discolouration, change of structure and
microbial spoilage.
The BIS has laid down specification for confectionery products. Standards
have also been developed for raw materials and additives. However, permitted
colours (Rhodamine-B and Metanil yellow) are still being used in preparation
of sweet meats.
263
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Chikki—A nutritious snack

A confection containing about 10-12% of protein which is good to eat,
inexpensive and with a good shelf life could help fight malnutrition of the
poor. The Indian traditional confection, chikki, could well serve this pur¬
pose. Chikki is very popular, particularly amongst children. It is produced
with minimum effort and it can be made on small scale and it has shelf-life
varying from 2-4 weeks, which can be increased up to 12 weeks with proper
packaging.
Chikki is a jaggery based sweet, commonly containing groundnut, but
also made from puffed gram, sesame, puffed rice, coconut scrapping and so
on, either individually or in combination. In the preparation of groundnut
chikki, groundnut with a low fat content yield a good quality product that is
also less susceptible to rancidity on storage. Groundnut is medium roasted
on a sand bath (120°-125°C). Jaggery should be hard, yellow or brownish
and have a high sucrose: glucose ratio. The jaggery is dissolved in colour
and have a high sucrose: glucose ratio. The jaggery is dissolved in an ad¬
equate amount of water and filtered to remove extraneous material. The
solution is heated to 145°-150°C, cooking on a medium flame after reaching
a temperature of 130°C, which imparts brittleness and a mild caramel to
the product. Groundnuts (or other ingredients) are transferred to the syrup
and mixed thoroughly till all the nuts get coated with jaggery syrup.
The hot mass is then transferred to wooden boards dusted with starch
using roller. It is spread and rolled to a thickness of about 8 mm. The rolled
mass is then cut into square slabs (sometimes, they are shaped into balls
depending on local consumer preference). One requires to master the skill
of quickly transferring, rolling and cutting before attempts. The slabs are
then removed from the board, cooled to room temperature, wrapped in suit¬
able wrappings, sealed and packaged in airtight tins. Chikki stored this way
will have a shelf life of 8-12 weeks.

BY-PRODUCTS OF SUGARCANE

Molasses
Molasses is dark coloured syrup product resulting after the removal of
crystalline sucrose by centrifugation from the concentrated clarified cane
juice. It amounts to about 3.6-4.5% of the cane crushed. In India, molasses
is obtained as a by-product chiefly in the manufacture of direct consump¬
tion white sugar and also in khandsari sugar manufacture. In other coun¬
tries, it is a by-product of raw sugar manufacture.
The composition of molasses depends on the way it is obtained in the
manufacture of various forms of cane sugar. Generally, it contains about
35% sucrose and 15% invert sugar.
Most of the molasses produced in the country is used in fermentation

264
 MISCELLANEOUS FOODS—SUGAR, JAGGERY AND COCOA BUTTER

industry for manufacture of industrial alcohol and potable spirits. Molasses

is also used as a flavouring agent in hookah tobacco, for feeding cattle and
indirectly in the manufacture of vinegar and yeast. Molasses obtained during
sulphitation process, which is light brown, with a characteristic tang and
flavour, is also used for edible purposes and in manufacture of confectionery.

Syrups
Cane syrup
Cane syrup is similar to molasses and is obtained by simply boiling
sugarcane juice to a syrup consistency. The term liquid sugar is used for
commercial products, such as a solution of sucrose and solutions contain¬
ing varying proportions of invert sugar. They are made from raw cane sugar
and their composition varies from pure sucrose to full invert sugar.
Corn syrup
Corn syrup is prepared by hydrolyzing corn starch with hydrochloric or
sulphuric acid with heat and pressure. The syrup is a mixture of glucose,
maltose and dextrin. The composition of the syrup is variable and depends
on the extent of hydrolysis. Glucose is the principal sugar and is present up
to 35%. The dextrin content varies from 30-35%. The presence of dextrin
makes the syrup inhibit crystallization of sucrose and other sugars and
thus corn syrup inhibit crystallization of sucrose and other sugars therefore
used when sugar crystallization is to be controlled.
Corn syrup may also be prepared by the enzymic hydrolysis of starch.
Enzyme hydrolyzed corn syrup contains a higher proportion of glucose and
less dextrin than acid hydrolyzed syrup. A combination of acid and enzyme
hydrolysis is sometimes used in the production of corn syrup. The syrup
thus obtained contains a high percentage of maltose.
High fructose syrup
Recently, a high-fructose corn syrup is prepared from corn syrup by the
use of the enzyme glucose isomerase. The enzyme converts half of the glucose
in the syrup to fructose. Because fructose has almost twice the sweetening
power of glucose, less syrup is needed to achieve the desired sweetening
with high-fructose corn syrup than is required when the regular corn syrup
is used. High-fructose syrup contains about 42% fructose and is used in the
manufacture of soft drinks, candies, preserves and some baked products.
Maple syrup
Maple syrup is prepared by evaporating the sap of the maple tree (Acer
saccharum). The sap contains sucrose and the syrup has sugar 64-68%.
The importance of the syrup is its special flavour. The sap as it comes from
the tree has no flavour but it develops as it is evaporated into syrup. Organic
acids present in the sap enter into the process of developing flavour by heat.
Maple syrup is used most frequently for sweetening pancakes and waffles,
and occasionally to add flavour and sweetness to baked products.

265
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

HONEY

Honey is produced by honeybees from the nectar of flowers and stored in

the comb. The flavour of honey depends on the nectar in question. Honey is
extracted from the comb, strained and marketed. Honey contains larger
quantities of fructose (about 38%) than glucose (31%). Sucrose constitutes
about 2% of the total sugar content. Honey has the capacity to retain water,
and hence cakes, candies, etc. made with honey remain moist for a longer
period than those made with other sweetening agents.

COCOA PRODUCTS

Cocoa is a very important raw material in confectionery. Because of rich

brown colour, exotic taste and aroma, it is favourite material for bakers, ice¬
cream producers and other food manufacturers. Its important use is in
production of chocolate and chocolate-coated or enrobed confectioneiy. A
large variety of goods like plain chocolate, milk chocolate, flavoured choco¬
late and chocolate coated nuts, wafers and biscuits are produced and they
are very popular.

Cocoa butter
Cocoa butter which accounts for more than 50% of cocoa bean is a
valuable by-product of the cocoa industry. The butter is mostly used in the
manufacture of chocolate.
The butter is a pale yellow liquid with a characteristic odour and flavour
of chocolate. It is brittle at temperatures below 25°C, softens in the hand
and melts (34°C) in the mouth. It is not greasy to touch. It is rich in satu¬
rated fatty acids (palmitic and lower acids 26.21%, stearic and higher acids
34.4%). Oleic and linoleic acids are present up to 37.3 and 2.1% respec¬
tively. The butter keeps well due to the presence of fat-soluble antioxidants
in it.

REFERENCES

Frazier, W.C. and Westhoff, D.C. 1978. Food Microbiology, pp. 281-291. Tata McGraw-Hill
Publishing Co. Ltd, New Delhi.
Magnus Pyke. 1982. Food Science and Technology, edn 4. John Murray Ltd, London.
Raghavendra Rao, M.R., Chandrasekhara, N. and Ranganath, K.A. 1989. Trends in Food
Science and Technology, (in) Proceedings of the Second International Food Convention
(IFCON-88), held at Central Food and Technology Research Institute, Mysore.
Rajaylakshmi, R. 1974. Applied Nutrition, pp. 239-241. Oxford & IBH Publishing Co., New
Delhi.
Shakunthala, M. N. and Shadaksharaswamy, M. 1987. Foods: Facts and Principles, pp.
335-357. Wiley Eastern Limited, New Delhi.
Swaminathan, M. 1988. Essentials of Food and Nutrition, vol.II, p. 51. Bangalore Printing and
Publishing Co. Ltd, Bangalore.
Thangam E. Philip. 1965. Modem Cookery for Teaching and the Trade, vol.l, pp. 501-534.
Orient Longmans Limited, New Delhi.

266
 MISCELLANEOUS FOODS—SUGAR, JAGGERY AND COCOA BUTTER

LEARNER’S EXERCISE

1. Explain stages of sugar cooking with suitable examples.

2. How high concentration of sugar preserves the foods?
3. Write in brief about (a) Khandari sugar, (b) beet sugar, (c) cube sugar, (d) brown sugar.
4. Distinguish caramalization and ciystallization.
5. Write about colours and flavours in confectionery.
6. Enumerate the various classes of Indian confectionery.
7. What are the by-products of sugarcane?

267
Part IV

Animal food products and

processing techniques
’
 Milk and
milk products

I ndia is now the largest producer of milk in the world with 74 million tonnes
in 1998-99 (Indian Agriculture, 1999). In the first decade after independ¬
ence (1950-60), the production was 17 to 20 million tonnes. There was no
drastic increase in its production in the next 2 decades. The production was
accelerated to reach 58.6 million tonnes in 1992-93. Success in raising the
level of milk production is ascribed to the operation flood project. More than
68,900 Dairy Co-operative Societies have been organized in 170 milk sheds,
involving about 8.8 million farmers by 1999 (Indian Agriculture, 2000). World¬
wide production of milk, in thousand metric tonnes, is given below (FAO,
2000).

Milk World Asia India

Cows milk, whole fresh 474,960 68,823 72,200

Buffalo milk 11,451 5,977 2,220

NUTRITIONAL COMPOSITION

Milk from different sources, regardless of breed or even species, will contain
the same classes of constituents. They are milk fat (3-6%), protein (3-4%),
milk sugar (5%) and ash (0.7%). Water accounts for the balance of
85.5-88.5%. All the solids in milk are referred to as total solids (11.4-14.5%)
and the total solids without fat is known as milk solids-non-fat (MSNF) or
solids-non-fat (SNF). The price of milk depends on its fat content and, to a
lesser extent, on its SNF content.
There are quantitative differences in the constituents of milk from dif¬
ferent sources; widest variations occur with fat, next with protein, followed
by milk sugar and minerals (ash). The yield of milk and its composition,
from the same source, vary depending on many factors. These include the
breed of the animal, its age, the stage of lactation, time of milking, time
interval between milking, season of the year, feed of the animal, condition of
the animal and so on.

Proteins
The main protein in milk is casein and it constitutes 3.0-3.5% of milk.

271
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

It is present as calcium caseinate in collidal suspension. When milk is con¬

verted into curd by lactic acid bacteria, a fine precipitate of casein is formed.
When milk is curdled by addition of lemon juice, casein is precipitated as a
flocculent precipitate. When milk is acted upon by rennin or pepsin in pres¬
ence of calcium salts, a thick curd of calcium paracaseinate is formed. This
is the basis of manufacture of cheese. Besides, casein, milk contains albumin
(lactalbumin) at a level of 0.5% and globulin (lactoglobulin) in small amount
(0.1%).

Fats
The fat content of milk varies from about 3.5% in cow’s milk to about
8% in buffalo milk. Fat is present in the form of fine globules varying in
diameter from 1-10 microns, the major portion having diameter of 3 mi¬
crons. Milk also contains small amounts of phospholipids and cholesterol.

Carbohydrates
The chief carbohydrate of milk is lactose. It is present up to 4.4-4.8%.
When milk is autoclaved, the colour becomes light brown. This is due to
reaction between the reducing group of lactose and the end amino group of
lysine residue in casein. This reaction is known as Maillard reaction.

Minerals
The important minerals present in milk are calcium, phosphorus, sodium
and potassium. The salts of these minerals function as buffers maintaining
the pH of milk at a constant level of 6.5-6.6. At this pH, casein exists mostly
as calcium salt in colloidal suspension. Calcium is essential for the formation
of curd from milk by the action of rennin (Swaminathan, 1988).

Enzymes
The enzymes of milk which are of interest to the food scientists are
alkaline phosphatase, lipase and xanthine oxidase. The enzymes in milk
are distributed throughout the entire system, some bound to the fat globules
surface, some associated with the casein micelles and some existing in free
colloidal systems.

Vitamins
Milk is a good source of both fat-soluble and water-soluble vitamins.
The concentration of fat-soluble vitamins except vitamin K, depends on con¬
centration of these vitamins in the feed consumed. Vitamin K is synthesized
in the cow’s rumen or tissues.
Milk is especially rich in riboflavin but this vitamin is lost rapidly on
exposure to light and may produce an oxidized off-flavour involving both
riboflavin and protein. The concentration of niacin and ascorbic acid is rela¬
tively low in milk.

272
 MILK AND MILK PRODUCTS

METHODS OF STERILIZATION

To ensure safe milk free from disease-producing bacteria, toxic substances

and foreign flavours, fresh whole milk is to be processed before marketing
(Magnus Pyke, 1982). The methods of sterilization of milk include clarifica¬
tion, pasteurization and homogenization.

Clarification
Noticeable quantities of foreign materials, such as particles of dust, dirt
and many other substances find their way into milk due to careless handling.
To remove these, milk is generally passed through a centrifugal clarifier.
Speed of the clarifier will be such that there is little separation of cream.
This operation removes all dirt, filth, cells from the udder and some bacteria.
Clarification does not remove all pathogenic bacteria from milk. The clarified
milk is ready for pasteurization.

Pasteurization
Pasteurization of milk is compulsory in modern milk operations, this
processing step is of primary importance. The process is essentially based
on the minimum temperature-time combination which will assure destruction
of all pathogenic bacteria which may be present in the raw milk. This can be
accomplished at various temperatures provided that the time is adequate.
Effect of pasteurization: Destroys any tuberculosis infection derived from
the cow and also other bovine infections such as Borucella abortus (causing
undulant fever). Streptococcus pyogenes (causing septic sore throat and scar¬
let fever).
• Reduces the number of milk souring organisms.
• Destroys bacteria accidentally derived from equipment, utensils and
milk handlers
• Does not affect chemical composition and the flavour of milk.
• Reduces small amount of vitamin ‘C’ that milk naturally contains.
There are 3 types of pasteurisation (i) Holder process (63-65°C for 30
min.) and (zz) Flash process (72°C for 15 sec) and (in) Ultra-high temperature
process.
Holder-process pasteurization: This involves following steps.
Milk is pumped through a stainless steel heat-exchanger
1
Passes across one side of a series of plates which are in contact with hot
water on the other side
I
Milk emerges from the heat exchanger and passes into a stirred tank
I
It is held for 30 min at 65°C
i
This tank is preferably fitted with a temperature recorder clamped to a

273
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

clock to ensure that the temperature is maintained long enough to de¬

stroy the bacteria
i
At the end of the 30 min. the milk is run out over a surface cooler or
through another heat - exchanges in which cold water is run counter -
current to the milk on reverse side of the plates
Flash pasteurization: Short time, high temperature pasteurization may be
used to treat a continuous flow of milk.
Pasteurizing units can be constructed in such a way to have the re¬
quired conditions of 72°C for 15 sec.

Raw milk
l
Regenerator (heated)
i
Flow access the other side of the heat exchanger plates

The milk is raised to pasteurizing temperature

i
Passes through the heater unit and remains at this temperature for the
time it takes to flow through holding tubes
I
It is then coolled first by passing through the regenerator and then
through the cooler
Ultra-High-Temperature (UTH) process: Long period storing for retaining its
palatability or protecting it from getting spoiled, the milk is heated to 132°C
for 1 sec. This can be done either by passing it through a heat-exchanger or
by the direct ingestion of live steam. After milk has been subjected to UHT
treatment, it must be packed under sterile conditions. A Swedish device for
packing with milk in sterile cartons is the so-called Tetra Pack Process.

HOMOGENIZATION

The process of making a stable emulsion of milk fat and milk serum by
mechanical treatment and rendering the mixture homogenous is homog¬
enization. This is achieved by passing warm milk or cream through a small
aperture under high pressure and velocity. Milk and cream have fat globules
that vary from 0.1-20 micron in diameter. High-pressure homogenizers,
low-pressure rotary-type homogenizers and sonic vibrators are used for the
purpose. The fat globules of milk and cream have a tendency to form into
clumps and rise due to their lower density than skim milk. When milk is
homogenized, the average size of the globules will be about 2 micron. Decrease
in size of the fat globules increases their number and surface area.

274
 MILK AND MILK PRODUCTS

The newly formed fat droplets are no longer coated with the original
membrane material. Instead, they are covered with an adsorbed layer of
plasma proteins, including casein micelles, micellar subunits and remnants
of membrane material. This brings about the stabilization of milk emulsion
and thus prevents rising of the cream and this process provides a uniform
or homogenous products.

PRESERVATION OF MILK

Milk is such a delicately flavoured, easily changeable food that many pres¬
ervation methods cannot be used without causing an undesirable change
or, at best, making a different food product. In fact, most of the products
from milk or cream evolved for the purpose of improving the keeping qual¬
ity. Milk and milk products, which serve to illustrate most of the principles
of preservation and spoilage of foods, have had more research done on them
than most other foods (Frazier and Westhott, 1978).

Asepsis
The prevention, as far as is practical, of the contamination of milk is
important in its preservation. Keeping quality is usually improved when
smaller number of microorganisms is present, especially those which grow
readily in milk.
Since the number of bacteria in milk is indicative of the sanitary pre¬
cautions and careful handling employed during the production, the bacterial
content of milk is used to measure its sanitary quality and historically, milk
has been graded on the basis of some method of estimating bacterial num¬
bers.
Packing serves to keep microorganisms from bottled milk, fermented
milk, packaged butter, canned milk, dry milk and packaged cheese and so
do the coatings of plastic, wax or other protective substances on finished
cheese. The bacteriological quality of the paper stock used in fabrication of
paper milk cartons has been examined. Normally, the packaging material
contributes very little to total microbial load in finished product.

Removal of microorganisms
After microorganisms have entered milk, it is difficult to remove them
effectively. The process of centrifugation, as in clarifying or separating will
remove some microorganisms from milk. High-speed centrifugation removes
about 99% of spores and more than half the vegetative cells of bacteria plus
some protein. However, the centrifugal procedure used for removing bacteria
from milk, known as bactofugation, is not used extensively on a commercial
basis. Moulds can be removed physically from the surface of some kinds of
cheese during curing process by scraping or periodic washing, but aside
from these limited instances physical removal is difficult.

275
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

USE OF HEAT

Pasteurization and ultra pasteurization

Because milk and cream are so readily changed by heat, the milk heat
treatment called pasteurization usually is used for preservation. The objec¬
tives of market milk pasteurization are to kill all the pathogens that may
enter the milk and be transmitted to people and also to improve its keeping
quality.
The first widely used pasteurization process for milk involved heating
the milk in large tanks or vats to 60°C for at least 20 min. This holding
method was subsequently changed to 61.7°C for 30 min. and finally to 62.8°C
for 30 min. to eliminate Coxigella burnetii, a rickettsia responsible for ‘Q’
fever which can be transmitted to milk. This was not a continuous process
and was referred to as vat pasteurization.
The use of plate heat exchangers and a continuous operation involves
high-temperature-short-time (HTST) pasteuriza-tion process at a tempera¬
ture of at least 72°C for at least 15 sec. The HTST is the most widely used
commercial pasteurization process today.
Heat-treatment process in excess of pasteurization of milk and milk
products have been designated as very-high-temperature (VHT) and ultra-
high-temperature (UHT) systems. There does not appear to be a precise
definition for a VHT system. The UHT processes usually refer to pasteuriza¬
tion techniques with temperatures of at least 130°C in a continuous flow,
with holding times of approximately 1 sec. or more. The current drawback
of UHT is that the severe heating needed could affect or alter the nutritive
and organoleptic properties of the product. The most popular of the UHT
systems are the direct heating methods, including a steam-injection-into-
milk process and a milk-injected-into-steam process, referred to as a steam-
injection technique and a steam-infusion technique respectively. The
combination of this type of heat treatment with aseptic packaging results in
a category of products usually referred to as sterilized milk or sterilized
cream.

Boiling
Boiling milk or heating in flowing steam destroys all microorganisms
except spores of bacteria and changes the appearance, palatability, digest¬
ibility, and nutritive properties of milk.

Steam under pressure

Evaporated milk is canned and then heat-processed by steam under
pressure, often with accompanying rolling or agitation. The forewarming of
milk at about 93-100°C or higher before evaporation kills all but the more
resistant bacterial spores. Sealed cans of evaporated milk are processed at
115°C-118°C for 14-18 min, which results in a commercially sterile product.

276
 MILK AND MILK PRODUCTS

USE OF LOW TEMPERATURES

With the exception of canned milk and dry milk, most dairy products re¬
quire use of low temperatures as one factor in their preservation, and often
it is the most important factor.

Refrigerated storage
For the production of good quality milk prompt cooling is essential after
it is drawn from the cow. The Grade A pasteurized milk ordinance of the
United States Public Health Service stipulates that Grade A raw milk for
pasteurization should be cooled at 10°C or less within 2 hr after being drawn
and kept that cold until processed. Newly pasteurized milk is to be cooled to
7.2°C or less and maintained there. It is preferable, of course, to cool it to
temperatures well below 7°-10°C.
Refrigeration temperatures are recommended for bottled milk or related
products during storage in plant or in retail market and during delivery and
in the home or restaurant until consumption. Some storage temperatures
are given in Table 33 for various dairy products.

Table 33. Storage conditions and sheif-life of various dairy products

Product Temperature Relative humidity Appropriate storage

(°C) (%) period

Cheese
Blue 0-1.1 70 3-6 months
Cheddar 0-1.1 70 12 months
Cream 0-1.1 70 4 weeks
Pasteurized and processed 0-4.4 6-10 months
Swiss 0-4.4 70 8-12 months
Milk
Evaporated and condensed 0 + 1 year
4.4 6-12 months
10 Few months
21.1 Few weeks
HTST 1.6-4.4 2-3 weeks
1.4-7.2 1-2 weeks
UHT 1.6-4.4 + 1 month
Non-fat dry milk 4.4 60 10 months
21.1 60 5 months
37.7 60 2 months

Freezing
Icecream and other frozen dairy desserts are frozen as part of manufac¬
turing process and are stored at low temperatures in the frozen state, where
microbial multiplication is impossible. Pasteurization, of course, reduces
the number and kind of microorganisms, but freezing kills relatively few of
the organisms and storage in the frozen state permits survival of most of the
microorganisms for a longer period.

277
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Butter in storage is held at -17° to -18°C or lower, where no microbial

growth can take place. Frozen cream is stored in considerable amounts at a
similar temperature. Milk, concentrated to one-third its volume, can be fro¬
zen at-17° to-18°C and stored at -23° to -24°C or lower and can be held for
several weeks without deterioration. Frozen milk can be concentrated by
freeze-drying methods.

Drying
Various milk products are made by removing different percentages of
water from whole or skim milk. Only in the manufacture of dry products
enough moisture is removed to prevent growth of microorganisms. Reduc¬
tion in moisture and consequent increase in the concentration of dissolved
substances in liquid condensed-milk products inhibit the growth of some
kinds of bacteria.
Condensed products: Evaporated milk is made by removing about 60% of
the water from whole milk, so that about 11.5% lactose would be in solution,
plus twice the amount of soluble inorganic salts in whole milk. This high
concentration of sugar is inhibitory to growth of some bacteria. Condensed
milk is more concentrated than evaporated milk and is still a poor culture
medium for organisms not tolerant of high sugar concentrations.
Dry products: Among the dairy products prepared in dry form are milk,
skim milk, cream, whey, butter milk, icecream mix and malted milk.
Dry milk is prepared either by roller process, or with or without vacuum,
or by the spray process. Milk and other liquid dairy products can be dried
by lyophilization, a process in which the quick-frozen product is dried under
a high vacuum. The moisture content of the finished dried dairy product
should be low to prevent growth of microorganisms, but survival of microor¬
ganisms in dry dairy product is variable.

USE OF PRESERVATIVES

Added preservatives
Addition of preservatives to dairy products is permitted only to a limited
extent. The use of sorbic or propionic acid or one of their salts is permitted
in cottage cheese, yogurt and some of the hard cheeses and processed
cheeses. The primary objective in adding a preservative to hard cheeses or
preserved cheeses is to prevent growth of moulds. Likewise the addition of
preservatives to cottage cheese and yogurt is to prevent growth of moulds on
the surface of product and to extend its shelf-life.
Added sugar acts as a preservative of sweetened condensed milk and
also it reduces the moisture, thereby making moisture unavailable to mi¬
croorganisms. Sodium chloride or common salt is added in the manufacture
of various kinds of cheese, but usually it is more of flavour or for controlling

278
 MILK AND MILK PRODUCTS

the growth of microorganisms during manufacturing and curing than for

preservation of finished product.
Carbonation of milk, butter, and icecream has been tried as an aid in
preservation but without much success. Cheese is smoked primarily for the
addition of flavour, although the drying, especially of the rind, and chemical
preservatives from smoke may improve keeping quality. Mold spoilage of
cheese is delayed or prevented when sorbic acid, propionic acid, sorbates or
propionates are added or incorporated in the wrapper.
The addition of hydrogenperoxide combined with a mild heat treatment
has been used for pasteurization of milk for certain kinds of cheese (e.g,
swiss and cheddar).

Developed preservatives
Most fermented products are microbiologically more stable or have a
longer shelf-life than initial substrate. Fermented milks and cheese are pre¬
served partly by developed acidity produced by the bacterial culture and
therefore have a longer shelf-life than fluid milk.

USE OF IRRADIATIONS

Although an effect equivalent to pasteurization can be obtained by treat¬

ment of milk with ultraviolet (UV) rays, this method is not used in preserva¬
tion of milk because only a thin layer of milk can be successfully irradiated
and unless great care is taken, a burnt flavour will result. Other uses of UV
light in the dairy industry include irradiation of rooms to reduce number of
microorganisms in the air in processing rooms where sweetened condensed
milk is being prepared or cut cheese is being packaged and in cheese-curing
rooms. The rays inhibit mould growth.
There are several types of milk products, consumed all over the world
and there are many different ways of making them. It is worthwhile to con- -
sider in detail a few selected processes (Raghavendra Rao et al, 1989) that
have come into vague in recent times and examine the possibility of their
utilization in the manufacture of dairy products with marketable potential
in India. The process are (z) Membrane technology reverse osmosis and ul¬
tra filtration, (n) UHT treatment of milk and milk products, and use of en¬
zymes in dairy technology.

Membrane technology
The main application of membrane technology (Reverse osmosis) in dairy¬
ing is the concentration of whey and to a lesser extent of milk to facilitate
handling, transport and storage. Reverse osmosis is being considered as the
initial step of partial concentration in drying of milk from the point of view of
energy saving. There is some activity for making icecream and yoghurt from
reserve osmosis concentrates instead of using milk powder. Trials are also

279
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

in progress for cheddar cheese making. Application of membrane processes

in the food industry includes concentration of milk, adjustment of protein
in milk, removal of salts and lactose from milk and whey concentration
(Nanjudaswamy, 1992). Concentrated milk could be utilized for later con¬
version into fluid products like flavoured milk, icecream, high protein milk,
preparation of cream and butter, yoghurt, dried products like whole milk
and skim milk powders, khoa, an important indigenous Indian milk prod¬
uct (Nanjudaswamy, 1992).

Ultra filtration
The first use of ultra filtration in the dairy industry was to fractionate
whey, concentrate the proteins for use in food processing and reducing the
pollution load of carbohydrate portion by making use of permeate. More
direct use to industry is the ultra filtration of milk for cheese making which
has become its widest application. Lesser applications are milk standardi¬
sation and making of fermented milks. The principal aim of ultra filtration
in cheese making is to include the whey products in cheese thereby increas¬
ing yield of the product.
Turning to possible applications in India, reverse osmosis is worth con¬
sidering as a means of reducing transport cost of milk. Bulk to be trans¬
ported can be reduced significantly if milk is first submitted to reverse osmosis
and the concentrate transported and diluted to milk at packaging dairy,
ultra filtration can be adopted in the initial concentration of milk for prod¬
ucts like shrikhand and yoghurt before to culturing. Trials are underway in
this direction.

Ultra high temperature treatment of milk

Ultra high temperature processing centres have been established in
dairies close to urban centres like Mumbai and Hyderabad to aseptically
pack UHT milk for distribution in these cities. The packaging material is
produced in a plant sponsored by the National Dairy Development Board.
Two kinds of packs are available, viz. one a Tetra-Palk in the form of a
tetrahedron which has a shelf-life of 3 weeks when stored under ambient
temperature i.e. without refrigeration and the other a Tetra-Brik, brick¬
shaped as the name implies, which has a minimum shelf-life of 3 months
without refrigeration.
A number of flavoured milk drinks formulated by the co-operative dair¬
ies and UHT treated and aseptically packed have also been introduced in
Gujarat and Delhi and their production is planned in Andhra Pradesh and
Tamil Nadu, and Kerala in near future.

USE OF ENZYMES IN MILK PRODUCTS

The enzymes proteinases, lipases, lactase and beta-galactosidase, are used

in milk products. _
280
 MILK AND MILK PRODUCTS

Proteinases are capable of clotting milk. The proteolytic activity of the

vast majority is too high relative to their milk clotting activity which results
in poor yield and quality of cheese. At present, 4 proteinases, bovine and
porcine pepsins and acid proteinases of Mucor michei and M. pusillus are
regarded as suitable substitutes of rennet.
Lipases cause considerable food spoilage through hydrolytic rancidity.
Compared with proteinases and carbohydrases, exogenous lipases have lim¬
ited application in food technology. They do have a few important applications
in dairy processing. The principal application of lipases is in cheese manu¬
facture, particularly hard Italian varieties. The special flavour of these vari¬
eties is due mostly to short chain fatty acids produced by the action of
lipases present in special kind of rennet paste used for their production.
Lactose is the most dominant carbohydrate in milk. The presence of
lactose in some food preparations is desirable, for example to stabilize flavour,
taste and texture and as a reducing agent to bring about Maillard browning
as a source of desired flavour and colour.
Beta-galactosidase is widely distributed in plant, animal and microbial
sources; only the enzymes from Aspergillus rtiger, Kluyveromyces lactis, K.
fragilis and E. coli are commercially available.

MILK PRODUCTS

Milk is used mainly as such or in the form of curd, butter and milk bever¬
age. It is used in the preparation of icecream, milk chocolates, malted bev¬
erages and milk sweets such as khoa, peda, gulab jamun, rasagollas, sandesh
etc. (Rajalakshmi, 1974).

Curd (Dahi)
It is the major product obtained from milk in India. Milk is fermented by
Lactobacillus and Streptococci bacteria which convert the lactose in milk to
lactic acid responsible for sour taste of curd. The difference in the flavour of
the curds is believed to be due to microorganism involved in fermentation.
The preparation of curd is a way of preserving milk. The growth of acid¬
forming bacteria prevents the growth of other microorganisms which cause
milk to spoil. During curd formation, the lactose of milk is converted into
lactic acid. There is some breakdown of protein increasing the non-protein
nitrogen. The fat globules coalesce and distribute themseles on the top physi¬
cally during curd formation. Milk proteins are jellied and a thin exudate of
clear serum on the curd is seen.

Buttermilk
It is obtained by adding water to curd and churning it or as a by-prod¬
uct in the process of preparing butter. Curd is used in preparation of bever¬
ages (lassi) by beating it with water and adding sugar or salt and spices.

281
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Butter
Butter making is an ancient process and involves separation of butter
from milk in which it is present as an emulsion. This separation is achieved
by churning, so that lighter fat layer floats on top. Either whole milk or
cream can be used for preparation of butter.

Ghee
It is prepared from butter by removing all the moisture. The other non¬
fat components separate out as cheesy particles. To get ghee with good
flavour as well as keeping quality, the butter should be heated till all the
moisture evaporates. When it is prepared just right the cheesy particles
separate out and are golden brown in colour. The ghee can be strained off
and cooled to room temperature.
Various forms of milk such as homogenized milk, evaporated milk and
non-fat dry milk are now available in the West. Homogenized milk is ob¬
tained by subjecting milk to temperature of 57°-60°C at 453.6-2268 kg
pressure through a very small orifice and in this process size of fat globules
reduces and the milk does not easily form a top scum. With the reduction in
size, the number of fat globules increases and there is a corresponding
increase in total surface area which increases the absorption of proteins
and phospholipids resulting in a high degree of emulsification.
Because of the larger surface area of fat globules, homogenized milk
increases thickness of certain products and coagulates more easily. The
cooking quality of homogenized milk therefore differs from that of non-ho-
mogenized milk when used in puddings etc.

Evaporated milk
The evaporation of milk is accomplished by removing a considerable
amount of water from whole milk. After removal of 60% of the water, prod¬
uct is homogenized and sterilized in sealed cans. The cooked flavour char¬
acteristic of evaporated milk is not usually detected in cooked food and
improves the flavour of certain foods such as those made with cocoa and
chocolate.

Condensed milk
Condensed milk is one which has been concentrated from full cream
milk by removal of its water with or without addition of sugar. The removal
of water is achieved at a relatively lower temperature by bringing down the
boiling point to 55°-63°C by reducing the pressure. The total milk solids are
not less than 28% and milk fat not less than 9.5%.

Toned milk
Toned milk has reduced fat content, the reduction being brought out by
either partial skimming or by addition of skim milk. Skim milk and fat are
also skilfully blended so as to give reconstituted milk.

282
 MILK AND MILK PRODUCTS

Dry milk
In this type of milk most of the water has been removed leaving a fine
creamy white powder. It is prepared from either whole milk or skim milk,
the latter giving a product with better keeping qualities. Non-fat dry milk
(skim milk powder) can be used with or without fat to replace fluid milk in a
recipe or to enrich the product. It can be either be reconstituted or used in
dry form.

Cheese
Cheese is classified as hard, semihard and soft cheese depending on
the moisture content. Cheese may be ripened by bacteria or moulds, or may
be unripened. The cheese that is directly made from milk is natural cheese
as opposed to processed cheese which is essentially melted or blended form
of the natural cheese. Whey cheese is made from the whey remaining after
coagulation and removal of casein.
The composition of cheese varies with the method of manufacture. The
protein content varies, being 20-25%, fat 30-35% and moisture 30-50%. It
also contains appreciable quantities of calcium, phosphorus and vitamins.
Cheese has thus a high nutritive value. About 150 g of cheese is equivalent
in food value to 1 litre of milk.
Cheese is made by coagulating or curdling of milk with acid or rennin or
both, drawing off the whey and processing the curd. Desirable flavour and
texture of cheese are obtained by curing (ripening), i.e. holding it for a speci¬
fied time at a specified temperature and humidity.
Manufacture of cheddar cheese is illustrative of the cheese manufac¬
turing process (Shakuntala and Sadaksharaswamy, 1987). Mostly pasteur¬
ized milk is used since pasteurization destroys undesirable enzymes and
most spoilage type organisms. The pasteurized whole milk is brought to a
temperature of 31°C and lactic acid-producing starter culture is added. The
required colouring matter is added at this stage. After about 30 min., to the
mildly acidic milk, renin solution is added, stirred and allowed to set. After
30 min. the milk forms a firm curd. The curd is then cut with curd knives
into small cubes. The removal of whey is easy from small cubes, which can
lead to a drier cheese.
After the curd is cut, it is heated so that the whey surrounding the curd
reaches a temperature of 38°C in 30 min. and is held at that temperature
for about 45 min. During this period the curd is stirred to prevent malting.
The whey formed due to heating is drained off and curd is allowed to mat.
Next it is subjected to the process of cheddaring. Matted curd is cut and
piled in 2 or 3 layers. During cheddaring operation, which takes 2 hr, acid
formation continues.
The cheddared curd is passed through a curd milk which cuts the slabs
into strips and whey is eliminated. The milled pieces are sprinkled with salt
and stirred for uniform distribution of salt. Addition of salt draws the whey

2831
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

out of curd by osmosis, and acts as a preservative, holds down spoilage

organisms and adds flavour to final product. The milled and salted curd
pieces are placed on hoops fitted with cheese cloth and the hoops are placed
in a hydraulic press under pressure overnight. The pressing determines the
final moisture content of the finished cheese. The processed cheese is al¬
lowed to dry by keeping in a cool dry place. To prevent mould growth and
excessive drying out during long period of ripening, the cheese is dipped in
hot paraffin. The waxed cheese is boxed and cured at 2.2°C and 85% rela¬
tive humidity for at least 60 days. For maximum flavour, ripening may be
continued for 12 months or longer.
Cottage cheese
This is made from skim milk. Similar process of preparation as in Ched¬
dar cheese is followed up to the stage of cutting the curd and removing
whey. The curd is then mildly salted, as a mild preservative measure and for
flavour. The curd may be blended with cream to obtain cream cottage cheese.
Cottage cheese is soft and contains 80% moisture.
Cream cheese
This is made by methods similar to the preparation of cottage cheese
using whole milk.
Other cheeses
Swiss cheese, which is a hard cheese like cheddar, is characterized by
formation of holes or eyes and a sweet nutty flavour. This is obtained by the
action of the organism Propionibacterium. This organism acts after lactic
acid organisms and produces propionic acid and carbondioxide. The propionic
acid contributes to nutty flavour and carbondioxide formed collects in pock¬
ets within the ripening curd-forming eyes.
There are a number of varieties of blue cheese. These are made from
cow milk except Roquefort which is made from sheep milk. There are a
variety of other cheese made in India on a small scale. These are paneer,
decca cheese, surti cheese, bandal cheese and chartna.
Panir {paneer): It is a cheese which can be compared to western cheese.
This is obtained by acid coagulation of milk containing more than 5% fat.
Milk is coagulated by adding 1% citric acid to heated milk and whey is
separated by squeezing out bag containing precipitate.
Decca cheese: This is made from whole milk. Milk is clotted with renin.
The cheese is made by breaking curd into small pieces and filling into wicker
baskets. A weighed board is placed on top to help drain whey. The weights
are removed after 10-14 days, when a thindry coat is formed on the surface
due to evaporation. The cheese is then smoked with wood or cowdung smoke.
It keeps for lor 2 months.
Surti cheese: This is made by precipitating curd by methods similar to
decca cheese preparation. The curd, without breaking, is transferred to small
wicker baskets to drain whey. Then it is immersed in acid whey containing
salt which makes it firm and salty. The cheese is drained dry. It has a short
keeping period of 10-14 days. _
 MILK AND MILK PRODUCTS

Bandal cheese: Bandal cheese is a cream cheese similar to surti except

that it is smoked. It is made from cream. It contains approximately 50% fat,
10-15% protein and 40% moisture. Its keeping quality is lower than that of
the smoked decca cheese.
Channa: This is very popular form of cheese prepared by addition of
lemon juice to boiling milk. The channa contains 4-5% fat. Citric acid may
be used for curdling milk. After the coagulation is completed, whey is sepa¬
rated by filtering through a thick cloth. Then bag containing precipitate is
pressed between boards to squeeze out remaining whey.

Traditional milk preparations

Several indigenous milk products are made on a cottage industrial scale
in India and used in preparation of sweets. Some of these milk products or
preparations are khoa, dudpeda, rasagolla, basundhi, srikhand, jamun and
ice cream.
Khoa: In India surplus milk is used for preparation of rabdi or (khoa\
Khoa is an important indigenous milk product. It is used as a base for
making various sweets. Khoa is nothing but dehydrated whole milk product
prepared by continuous heating of milk in a pan over direct fire. During
heating, milk is stirred constantly till it reaches a semisolid dough consist¬
ency.
During preparation of khoa, milk proteins are coagulated. This is accel¬
erated by incorporation of air and frothing during stirring. Because of ap¬
preciable homogenization during vigorous boiling, when coagulation of protein
sets in, all the fat globules are entrenched in coagulant. Similarly, water is
dispersed and therefore khoa does not appear to be wet. Lactose will be
present as an anhydrous sugar in khoa when it is hot and its crystallization
on cooling is not favoured because of high viscosity of products. There is a
decrease in vitamin A and some water-soluble vitamins of milk in formation
of khoa.
Khoa is obtained from cow or buffalo milk or mixed milk. Buffalo milk is
generally preferred, as it is more in solids. Composition of khoa depends on
composition of milk (Swaminathan, 1988; Raghavendra Rao et al, 1989).
General composition of khoa: The khoa contains following:

Composition Cow milk (%) Buffalo milk (%)

Moisture 25.6 19.2

Fat 25.7 37.1
Protein 19.2 17.8
Lactose 25.5 x 22.1
Ash 3.8 3.6

Types of khoa making: Khoa can be made by direct fire method, con¬
tinuous, automatic method and hot water or steam method (indirect heating).

285
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Khoa is used in preparation of various types of milk sweets and is con¬

sumed as such with the addition of sugar. Khoa is an ingredient of several
Indian sweets. However, these products are sold at a high price. Sandesh is
prepared from cheese separating from whey. The separated cheese is kneaded
with powdered sugar and pressed into desired shapes to make sandesh.
The kneaded cheese is shaped into balls and steeped in sugar syrup for a
few hours to form rasagollas.
Khoa is mixed with powdered sugar, kneaded well and shaped into de¬
sired shapes to form peda. Nuts such as pistachio are sprinkled on top and
product is coloured.
Gulab jamun: Khoa is mixed with a little flour, curd and baking soda,
kneaded well, rolled into balls, deep-fried in ghee or hydrogenated oil at a
low temperature and the fried balls put in thin syrup to form gulab jamuns.
Saffron and rose water may be added to the syrup. Milk and baking powder
can be substituted for curd and baking soda.
The preparation of khoa, needed for making gulab jamun, is a time con¬
suming process. Gulab jamuns can also be prepared from milk powder. As
khoa contains about 33% fat and 17% moisture, a product resembling khoa
can be made by kneading together 6 parts of volume of skim milk powder,
1 % parts of ghee or hydrogenated oil (or 7-8 parts of whole milk powder and
a little ghee) 2 parts of curd, 1 part of maida and baking soda or baking
powder (1/4-1/2 teaspoon for 3 cups of milk powder). The dough is shaped
into balls, deep-fried and put in sugar syrup prepared from 8 parts of sugar
and 12 parts of water.
Basundhi: It is prepared by heating milk for a prolonged period at a low
heat so that some cheesy particles are formed. It is then sweetened, sea¬
soned and served as a dessert.
Icecream: One of the other milk products which is very commonly con¬
sumed and liked by all is the icecream. Icecream is a very popular product
in western countries. It is becoming popular in our country also.
Icecream is a frozen dairy product. It contains a variety of dairy ingredi¬
ents. These include whole milk, skim milk, cream, butter, butter oil (which
contains 99% butter fat), condensed milk products and dried milk prod¬
ucts. The composition of icecream varies, depending on the ingredients used
in its preparation. The percentage composition of a good icecream is milk fat
12, milk solids non-fats 11, sugar 15, stabilizer 0.2, emulsifier 0.2% and a
trace of vanilla. This composition is exclusive of air, i.e. they are based on
the weight of icecream mix (Shakunthala and Shadaksharaswamy, 1987).
Srikhand: It is a semi-soft, sweetish sour whole milk product prepared
from lactic fermented curd. The curd is partially strained through a cloth to
remove the whey and thus produce a solid mass called chakka (the basic
ingredient for srikhand). This chakka is mixed with required amount of sugar
(about 10% of milk) to yield srikhand. The srikhand is further dessicated to
a headmass by heating over an open pan to make srikhand vadi.

286
 MILK AND MILK PRODUCTS

Composition: The composition of chakka will depend on the initial com¬

position of milk, the degree of fermentation, i.e. acidity developed, and the
extent of whey removed. These 3 factors together with the amount of sugar
added influence composition of srikhand.
The composition of srikhand vadi depends on the extent to which
srikhand is dessicated.
Milk and milk products are easy to digest, highly relished and well tol¬
erated by groups such as infants and convalescents.

Milk beverages
Skim and low-fat milks: Skim milk is milk from which the fat has been
removed by centrifugation. The content of skim milk is usually about 0.1%.
The 2% milk contains 2 per cent milk fat. It is made from fresh whole and
skim milk and is pasteurized and homogenized. It may be enriched with
non-fat milk solids.
Concentrated milks: Concentrated milk may be fresh, frozen, evaporated,
condenced or dried. Milks are concentrated by removal of water in varying
amounts. They may be reconstituted to their original form.
Concentrated fresh milk is first pasteurized and homogenized and then
has two-thirds of water removed at low temperatures under vacuum. This
3 : 1 concentrate, standardized to about 10.5% fat, is rehomogenized,
repasteurized, and packaged. Eventhough perishable, it will retain its sweet¬
ness and flavour under refrigeration for about 2 weeks or as long as 6 weeks
at near freezing temperatures. This milk is not available in many communi¬
ties.
Concentrated fresh milk may be quick-frozen and held at-23.3 to -30°C
for keeping longer periods. It should be used soon after defrosting. Steri¬
lized milk is aseptically packaged in cans. This product would keep up to 3
months of room temperature or longer periods of time under refrigertion.
Evaporated milk is the whole milk that has slightly more than half the
water evaporated in a vacuum, A forewarming period of 10 min. is effective
in preventing coagulation of the casein during the sterilization period after
the product is homogenized and canned. High-temperature short-time steri¬
lization has been shown to produce the best product in both colour and
flavour. Most of the evaporated milks in the market are fortified with 400
International units of vitamin D concentrate per quart.
Theoretically, sterilized and evaporated milks keep indefinitely until
opened but on long standing the homogenized fat particles tend to separate,
thus breaking the emulsion. Cans of evaporated milk and condensed milk
should be turned every few weeks because the solids tend to settle.
The browning of evaporated milk and condensed milk is probably of the
Maillard reaction type (sugar-protein interaction) and occurs during both
sterilization and storage. The rate of browning is greater at room temperature
and with longer time of storage. Some amino acids are also lost on long

287
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

storage at room temperature or above. The best storage temperature tor

evaporated milks is 4.4°C.
Sweetened condensed milk has about 15% of sugar added to the milk,
after which the product is concentrated to about one-third its former volume.
Because the 42% sucrose content of the finished product acts as a pre¬
servative, the milk is not sterilized after canning. Federal standards require
28% total milk solids and 8.5% milk fat.
Non-fat dry milk powder is usually made from fresh pasteurized skim
milk by removing about two-thirds of the water under vacuum and then
spraying this concentrated milk into a chamber of hot filtered air. This proc¬
ess produces a fine powder of very low moisture content, about 3%. The
roller process, in which the milk is sprayed on the surface of heated metal
cylinders may also be used in drying of milk. Milk powder may be treated
with an additional instantizing process, so that it will disperse in water
more readily. The substance is remoistened and redried to form larger ag¬
glomerated particles than regular non-fat by milk. Evidently more water-
soluble substances are on the outside of the larger particles, thus enhancing
the ease of dispersion in water.
Dried whole milk is made from fresh whole milk with water removed by
the same procedure as is used for non-fat dry milk. Dried whole milk contains
not less than 26% milk fat and not more than 5% moisture. Because of the
fat content it has a poorer keeping quality than dried skim milk but methods
have been developed for manufacturing dried whole milk of improved keeping
quality. It should be kept cool and dry. Another dried dairy product is but¬
termilk, which has a rather wide use in commercial flour mixes. Dried milk
whey solids are also available and are used in some commercial baked prod¬
ucts.
Consumer acceptance of dried milks requires that procedures for manu¬
facturing, packaging, and storing result in a palatable product that retains
its original nutritive value and that is easily redispersible if the milk is to be
used in liquid form.
When dried milk is reconstituted, powder is added to water and is shaken
or stirred. If used in flour mixture and some other products, the dry milk
may be mixed with dry ingredients or with melted fat. The quantity of instant
milk powder to use for one quart of fluid milk is usually one and one-third
cups.

Homogenization
Most whole milk today is homogenized immediately after it is pasteurized.
Evaporated milk is also homogenized. Homogenization consists of forcing
milk or cream under pressure through a small aperture in a machine called
a homegenizer to break up the fat into much smaller globules which will
remain dispersed. The amount of pressure used partly determines the size
of fat particles. Temperature is also a factor, the degree of dispersion in-

1288
 MILK AND MILK PRODUCTS

creasing from 40 to 65°C and reaching its maximum at 65°C F.A film of
absorbed protein immediately surrounds each of new globules and prevents
them from reuniting. It is estimated that about one-fourth of milk protein is
adsorbed on finely dispersed fat particles of homogenized milk. No cream
line forms and the increased dispersion of fat imparts richer flavour and
more body to the milk.
The greatly increased surface exposed in highly dispersed fat of homog¬
enized milk increased the tendency towards development of rancidity, be¬
cause it destroys the enzymes that could otherwise attack the more highly
dispersed fat.
Canned and frozen whole milks: Fresh whole milk that is homogenized may
be sterilized at 132.2- 137.7°C for 8-10 sec., after which it is canned asep-
tically. It may be stored at room temperature until opened, then it must be
refrigerated. The brief high-temperature heating is said to produce only slight
cooked flavour. Canned whole milk is available chiefly for use on ships or
for export to other countries where milk is less abundantly produced.
Pasteurized, homogenized, whole milk can be quick-frozen but it keeps
best if held below -23.3°C until used. It should be used soon after defrost¬
ing. Unless quick-frozen milk is held at the above low temperature, the
physical characteristics change as mentioned previously. The milk may also
develop an off-flavour.
Quick-frozen human milk has been prepared and used successfully for
infant feeding.
The principal advantage of frozen, homogenized and pasteurized milk is
that it can be shipped to distant areas where milk is needed and not other¬
wise available.
Soft-curd milk: Natural milk from some cows form a softer curd during
digestion than that from other animals. Natural soft-curd milk has a lower
percentage of casein, calcium, and phosphorus than does average milk. The
manufacture of soft-curd milk has been accomplished by the removal of
about 20% of original calcium and phosphorus and by a brief digestion with
pancreatic enzymes. Digestion period preceedes pasteurization which
destorys enzymes, thus stopping digestion at desirable stage. The soft curd
is suitable for infant feeding for all cookery purposes. Now almost all fresh
fluid milk sold is homogenized, and thus has a relatively soft curd, the
product labelled soft-milk prepared by other processes is seldom seen.
Low-sodium milk: Fresh whole milk may be passed through as ion-ex¬
change resin to replace 90% or more of its sodium with potassium. The low-
sodium milk produced is pasteurized and homogenized and may be canned
or dried. Some B vitamin and calcium are lost in processing but this milk
has special uses in sodium-restricted diets.
Malted milk: It is a dried mixture of whole milk and other liquid obtained
by cooking barley malt and wheat in water. Some malted milks used for
beverages are flavoured with chocolate (Osee and Bennion, 1970).

2891
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Cultured milks: Milk sours when lactic acid bacteria produce acid up to
0.3%, but coagulation of casein does not occur until acidity reaches 0.6-0.7%.
Although milk which sours naturally is not much used for beverage purposes,
acidophilus milk produced by inoculating fresh milk with a pure culture of
Lactobacillus acidophilus bacteria is commonly used in some countries. Such
types of milk introduces acidophilus bacteria into the intestine, where they
retard the development of putrefactive organisms. Acid milk is also sometimes
used in infant feeding.
Ordinary buttermilk, which is a by-product of churning sour cream into
butter, may be used for drinking and cooking purposes.
However, commercially produced buttermilk is a cultured product, usu¬
ally made from fresh skim milk. Pasteurized skim milk is cultured chiefly
with Streptococcus lactis and incubated at 20°-22.2°C. until the acidity is
0.8-0.9%, expressed as lactic acid. Butter granules are sometimes added in
amounts that produce 1% or less fat in the butter milk.
Yoghurt is usually cultured from partially skimmed milk with the addi¬
tion of a mixed culture of one or more strains of microorganisms, such as
Streptococcus thermophilus, Bacterium bulgaricum, and Plocamobacterium
* yoghourtii. The milk is pasteurized, homogenized, inoculated, and incubated
at 3.7°C. Yoghurt contains about 11-12% milk solids and has a sharp, tangy
flavour. It is often sold with added sweetened fruit and may be served as a
dessert.
Flavoured milk and milk drinks: A flavoured milk is whole milk with a fla¬
voured syrup or powder and sugar added. A flavoured milk drink is skim or
partially skimmed milk similarly flavoured and sweetened. Such milk is
pasteurized and usually homogenized. Chocolate milk usually contains 1%
cocoa with 5% sugar and less than 1% stabilizer.

Filled and imitation milks

Filled milk is made by combining fats or oils other than milk fat with
milk solids. The resulting product appears very much like milk. The Federal
Filled Milk Act specifies the type of milk solids as any milk, cream or skimmed
milk, which may be condensed, evaporated, concentrated, or dried, if de¬
sired. Imitation milk resembles milk in appearance but contains no milk
products as does filled milk. Ingredients such as water, corn syrup solids,
sugar, vegetable fat, and a source of protein like sodium caseinate or soya
protein may be used in imitation milks. Coconut oil is commonly used as
vegetable fat. Both types of filled and imitation milk are subject to variable
state regulations but are not as yet governed by the same rigid sanitation
and composition requirements as pasteurized Grade A milk or milk product.
The Milk Ordinance and Code recommended by the U.S. Public Health
Service formulates grades and standards for the production and
merchandizing of dairy products. The Code was formulated as a guide for
state, city, and rural communities interested in protecting their milk supplies.

290
 MILK AND MILK PRODUCTS

Grades of milk are designated in some areas for both raw and pasteur¬
ized milk. The grades are based on the conditions under which the milk is
produced and marketed, and on the bacterial count of the finished product.
Grades and their meanings vary according to local regulation unless the
Ordinance and Code of the U.S. Public Health Service have been adopted, in
which case standards are uniform. The milk supplies of much of the United
States are covered by the Ordinance. Under the Ordinance, Grade A desig¬
nates quality fluid milk and is the grade delivered to consumers and sold in
retail stores. The milk used for manufacturing milk products is designated
as manufacturing grade (Osee and Bennion, 1970).
A processor must operate his plant under continuous inspection if he
wants to use the U.S. Department of Agriculture Grade Shield on his milk
packages in this voluntary, fee-for-service programme. The U.S. Extra Grade
Shield on dry milk indicates high quality and wholesomeness (Joshua, 1971).

Certified milk
Certified milk may be either raw or pasteurized. The quality of milk
must confirm to and be under the constant supervision of the American
Association of Medical Milk Commissioners. Bacterial count is defined and
certain conditions of production are imposed that result in a milk of high
quality and low bacterial content. But because low bacterial count does not
necessarily mean freedom from pathogenic bacteria, most certified milk is
now pasteurized. Although little of the milk of commerce is certified milk,
the movement behind its production as safe milk for infant feeding has had
the effect of improving all dairy practices and of raising the sanitary quality
of all marketed milk.

Fermented milk
Since milk goes bad very soon, it is converted into sour milk which is
acidic and hence will keep for a longer time. Milk from different animals and
different organisms are used for preparation of fermented milk in various
countries. The consumption of soured-milk preparations is widespread be¬
cause of their supposedly therapeutic value and also because they do not
get spoilt as easily as milk. They appear under various names which iden¬
tify the country in which they are produced (Joshua, 1971).
Curd: It forms an essential part of the diet in India and Ceylon. Curd is
prepared from cow’s or buffalo’s milk which is boiled, cooled and while still
slightly warm, inoculated with a few drops from the previous day’s curds.
When allowed to ferment only for 5 or 6 hr, the curds are not sour, but
within 10-12 hr, they become acidic. The organisms responsible for con¬
verting milk into curds are Streptococcus lactis and Lactobacillus.
Yoghurt: It is the sour milk preparation of countries like Bulgaria and
Turkey. This is usually prepared from camel’s or mare’s milk, though milk
from other animals like the cow are also sometimes used. The fermentation
is produced by acid-forming organisms like Lactobacillus bulgaricus\ some-

2911
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

times yeasts are also present and produce a small amount of alcohol and
carbondioxide.
Kumiss: This is fermented milk prepared by the action of yeasts, lactobacilli
and streptococci on mare’s or cow’s milk used in Russia. The yeast pro¬
duces alcohol and carbondioxide and the bacteria produce lactic acid.
Leben: It is the sour milk prepared in Egypt from cow’s milk or goat’s
milk or buffalo’s milk, by the action of lactic acid producing bacteria and
yeasts. The bacteria hydrolyse the lactose to glucose and galactose; some of
the sugar is then fermented by the yeasts with the production of alcohol and
carbondioxide and some converted into lactic acid by bacteria.
Kefir: It is prepared by the addition of kefir grains to milk. Kefir grains
are cauliflower like aggregates of a mixture of microorganisms chiefly
Saccharomyces, Lactobacillus casei and Streptococcus lactis and S. cremoris.
The yeasts produce alcohol and carbondioxide and the bacteria produce
lactic acid.
Matzoon: It is the sound milk preparation of Armenia and is similar to
yoghurt in flavour and microflora.
Gioddin
Gioddin: Gioddin is the fermented milk preparation on the island of Sar¬
dinia. It contains the same organisms as Bulgarian yoghurt and Armenian
matzoon.
Taette: It is a ropy butter milk made by means of a ropy variety of
Streptococcus lactis.
Skyr: Skyr is a semisolid fermented milk in which chiefly, Streptococcus
thermophilus and Lactobacillus buglaricus have been active.

REFERENCES

Agriculture. 2000. Economic Intelligence Service Centre for Monitoring Indian Economy Pvt
Ltd, Mumbai.
Frazier, W.C. and Westhoff, D.C. 1978. Food Microbiology, pp. 281-291. Tata Me Graw-Hill
Publishing Company Ltd, New Delhi.
Indian Agriculture, 1999. Indian Economic Data Research Centre, 13-173. Panchvati, New
Delhi.
Joshua, A.K. 1971. Microbiology, edn 1, pp. 122-34. The Indian Printing Works, Mylapore,
Madras.
Nanjundaswamy, A.M. 1992. Membrane processes in Food Industries. Food Digest 15(2):
173-83.
Osee, H. and Bennion, M. 1970. Introductory Foods, pp. 236-74. The Macmillan Company,
Collier - Macmillan Limited, London.
Raghavendra Rao, M.R., Chandrasekhara, N., Ranganath, K.A. 1989. Trends in Food Science
and Technology, (in) Proceedings of Second International Food Convention (IFCON-88),
held during 18-23 February 1988 at Central Food and Technology Research Institute,
Mysore, pp. 388-402.
Rajalakshmi, R. 1974. Applied Nutrition, pp. 239-241. Oxford & IBH Publishing Co., New
Delhi.
Shakunthala, M. N. and Shadaksharaswamy, M. 1987. Foods : Facts and Principles, pp.
335-357. Wiley Eastern Ltd, New Delhi.

292
 MILK AND MILK PRODUCTS

Swaminathan, M. 1988. Essentials of Food and Nutrition. Bangalore Printing and Publishing
Co. Ltd, Bangalore, Karnataka.

LEARNER’S EXERCISE

1. Discuss the relative merits and demerits of the various processing techniques of milk.
2. Write the composition of different kinds of milk.
3. Why is milk considered a complete food? What are its uses in food preparation?
4. Explain the factors responsible for souring and gas production in milk.
5. What are the effects of heat processing on milk?
6. Write the following in brief:
(a) Membrane technology
(b) Homogenization
(c) Ultra filtration
7. Write about various milk products.

293
20
E ggs are a good and an important source of portein in the human diet.
Egg is a complete and perfect food by itself. Eggs of all birds may be
eaten, but in India eggs of hen and duck are mainly utilized for human
consumption. It is an ideal protective food owing to presence of important
essential amino acids. Thus egg protein is termed as reference protein. Our
Indian diets are mostly deficient in lysine and methionine. Since egg is rich
in these amino acids, it supplements the diet. Production of eggs is repre¬
sented in Fig. 38 (FAO, 2000).

Fig. 38. Egg production (million tonnes) during 1999-2000

STRUCTURE

The egg is composed of shell, white and yellow or yolk. The shell of an egg is
covered with a protective coating that aids in maintaining freshness of the
egg by covering the innumerable minute holes in the shell. If this mucin
layer or bloom is removed, the egg spoils due to entry of microorganisms,
which hasten the deterioration of quality.
Within the shell there are 2 membranes—the outer and the inner mem-

294
 EGGS

brane. The egg white is made up of 3 layers, of them 2 are thin and hold the
thick layer between them. The yolk is creased in the vitelline membrane and
held in the centre of the egg white by 2 cord like structures which are called
chalazae. Indistinct spot on the yolk is germ spot or blastoderm, beneath
which extends a white column called latebra. The yolk is made of alternate
layers of white and yellow (Fig.39).

Fig. 39. Structure of an egg of hen (Source: Mudambi and Shalini, 1993)

NUTRIENT COMPOSITION

The composition of the egg white is quite different from that of the yolk. Of
importance is the large amount of water (87%) and absence of fat in the
white, as contrasted with the reduced amount of water (49.5%) and large
quantity of fat (33.3%) in the yolk. The white contains protein albumin,
whereas the yolk consists of fat, fat-soluble vitamins, water-soluble vita¬
mins and minerals. Nutritionally, eggs are very rich and provide almost all
nutrients at a reasonable cost.
Protein content of eggs is 13.3% and is of excellent quality, containing
all essential amino acids required by man, hence are of vital importance
especially during childhood, adolescence, pregnancy and lactation. They
also contain 13.3% fat, hence eggs provide 173 Reals/100 g. Eggs also con-

295
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

tain fat-soluble vitamins, A, D and E. The water-soluble vitamins thiamine,

riboflavin, niacin, pyrodoxine, pantothenic acid and vitamin B]2 are also
present in eggs. Minerals like calcium, phosphorus, iodine, sodium and
iron are present in egg in good amounts. Cholesterol content of egg yolk is
high, thus egg yolk restricted in patients suffering from cardiac and liver
diseases.

CHANGES DURING STORAGE

The egg starts deteriorating soon after it is laid. Therefore eggs should be
refrigerated promptly after they are collected. The air cell in a good-quality
egg is less than 0.3 cm deep. The yolk is in the centre. When the egg is
broken the condition of yolk and white can be observed. The yolk is firm and
stands up in the centre of white, which is viscous. The egg white forms a
definite ring around the yolk and thick white holds its shape. No blood spots
are present and there is no bad odour (Mudambi and Shalini, 1993).
Factors which affect quality of eggs include age, atmosphere and tem¬
perature of storage, relative humidity and any pre-treatment given before
storage.
A number of changes occur in egg during storage (Fig. 40). These in¬
clude:
(i) The air cell increases in size due to loss of moisture.
(zi) Carbondioxide is lost resulting in increased pH.
(iii) Water passes from white to yolk, thus the size and fluid content of
yolk increase. Due to pressure of the enlarged yolk the vitelline
membrane weakens and eventually breaks.

A fresh egg

A stale egg
(a)

Air cell Enlarged and

Enlarged
air cell displaced air cell

(b)

Fig. 40. Changes during storage of egg. (a) egg quality, (b) air cell

296
 EGGS

(iv) The thick egg white becomes less viscous and it changes to a watery
white fluid which runs easily.
The extent of spoilage in eggs can be assessed both by external and
internal examination. Externally the egg is examined for a good shape of
74-75 Index and must weigh around 55-58 g with a sound and clean shell.
The criteria given here indicate the extent of quality of egg. The egg can
be termed as spoiled if the air cell size, albumin and yolk index increases.
The common indicators such as size of air cell, albumin index, yolk index
and thickness of shell used to determine the spoilage in eggs are given in
Table 34.

Table 34. Indicators to determine spoilage in eggs

Criteria Range

Air cell size 2-3 cm

Albumin index 0.08-0.1
Yolk index 0.35-0.45
Haugh (unit score) 80 or above
Thickness of shell (mm) 0.35 or above

The extent of spoilage in egg for all practical purposes is done by break¬
ing and testing the albumin, yolk and haugh indices. But for marketing
purposes, any spoilage is determined by 2 methods called candling and
grading.

Candling
Egg is placed against a small aperture from which a sharp, bright light
passes through the content of the egg. The albumin, yolk, size of air cell,
presence of any blood clots or extraneous matter is checked. This method is
most commonly used in determining the spoilage in eggs.

Grading
The parameters like thickness, size and colour of the shell and weight
of the egg are considered for determining the spoilage. The weight reduces
as the extent of spoilage increases, the thickness of shell decreases and
shell becomes creamy in colour (OTA, Canada 1961).
Appropriate care must be taken in preventing the spoilage and to pre¬
serve eggs for longer life. Certain preservation methods have to be followed.
The purpose of preservation is to:
(a) Prevent embryonic development (among fertile eggs).
(b) Retard process of evaporation and shrinkage.
(c) Counteract changes causing liquification and ongress of water into
yolk.
(d) Check against microbial contamination (rots and moulds).

297
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

(e) Avoid development of undesirable odours and flavours.

(/) Ensure supply of high-quality eggs to consumers.
Eggs can be preserved as whole egg in shell or in liquid or processed
foods.

PRESERVATION OF SHELL EGGS

Shell eggs are preserved by 4 methods (Siddiqui, 1975).

Wet immersion methods

This method is used under village conditions for small-scale operations.
In the wet method, only infertile, fresh, good-quality eggs should be
used. Materials used for preservation should not impart undesirable taste
or odour. Prevention of deterioration of solutions is a necessary precaution.
Gaseous exchange between eggs and the surrounding atmosphere should
be prevented. There are 2 types of wet or immersion methods.

Lime water or lime sealing method

A saturated solution of lime water is used. When eggs are held in lime
water, C02 released from the eggs combines with it to form calcium carbon¬
ate which deposits and seals shell pores. The reaction is completed in 16 hr.

Ca (OHJg + CO —^ CaC03 + H O
2 2

About 0.45kg of quick lime is mixed with 0.568 litre of water and stirred
well. After the reaction is over, 113.6 g salt is added to increase the specific
gravity, so that the eggs do not strike hard against the bottom of container
when immersed. Further 2.56 litres of water is added and stirred. The solu¬
tion is filtered through a muslin cloth and to filtrate a small quantity of
slaked lime is added to maintain the concentration. Eggs are gently lowered
and held in the solution for 14-16 hr and later removed and stored at room
temperature. Such eggs can be stored for 3-4 weeks.

Water glass method

A 10% solution of sodium silicate, commonly called water glass, is used.
The colloids absorb and block the shell pores without any chemical reac¬
tion. Water is boiled thoroughly to remove the dissolved carbondioxide which
otherwise forms a complex with sodium silicate. The calculated amount of
chemical is added to prepare solution. The eggs are dipped in cooled water
glass solution. The solution is most effective at 23.9°-26.7°C. Eggs are to be
kept overnight, later removed and stored at room temperature.

Dry methods
Oiling: Eggs may be treated with oil using suitable, light weight, mineral
oils which are colourless, odourless and tasteless. Standards of egg coating

298
 EGGS

mineral oils are: specific gravity, 0.83-0.84; viscosity, 50 poises; colourless;

pour point, -3.9° to 1.7°C flash point, about 137.8°C and reaction, neutral.
Coating with oil seals shell pores and thus evaporation of water, C02
and other changes are prevented, thus preserving egg quality. Oiling is car¬
ried out by dip method or spray method.
Dip method: Eggs are dipped for a few seconds in the oil, withdrawn and
allowed to stand to drain off the excess oil. This oil could be heated (82.2°C
for 20 min.), filtered, cooled and reused. About 400 ml oil is required for
200-250 eggs. Sometimes oil is prewarmed to maintain slightly higher tem¬
perature than that of eggs required to be dipped.
Spraying method: The eggs are kept broad end up in egg-filler flats and
the oil is sprayed with a sprayer to cover one-half to three-fourth of the shell
surface. A 400 ml oil is sufficient to spray 1,000 eggs. Bactericides and
fungicides may be added to the oil. Spraying oil is less expensive and requires
less labour than oil dipping. Oiled eggs are preserved up to 3 weeks at room
temperature.
Gaseous atmosphere: Some kind of overwrap along with inert gases is used.
Eggs are kept in plastic bags or retail cartons, filled with gas and sealed.
Maintenance of higher C02 pressure surrounding the eggs precludes C02
loss thus preserving egg quality. This is not a convenient method in view of
cost and hazards to workers.

Thermostabilization or heat treatment methods

In this method heat is used. Even fertile, fresh eggs can be preserved by
destroying the viable germ. Eggs are thermostabilized by immersing shell
eggs for 15-20 min. at 55°C while water is constantly stirred. This results in
fine film of peripheral albumin immediately next to the shell being coagu¬
lated (Kandilkar et a/., 1972). Coagulation inhibits C02 loss. Different heat
treatments can be used:
48.9°C for 35 min.; 66°C for 5 min.; 57.2-100°C for 15 min. (defertili¬
zation); 100°C (boiling water) for 3 to 5 sec.
This is called flash treatment. Thermostabilized eggs can be stored at
room temperature for 3-4 weeks.

Cold storage or refrigeration

It is of 2 types.
Long term storage: Eggs are stored at a temperature of about -1.1°C and
a 85-90% relative humidity. A suitable insulated room is required, and an
anteroom to avoid entry of air. Proper air circulation is important to help
loss of heat from eggs. Cold temperature storage should not be less than
28°F (-2.2°C). Eggs keep well for a long time up to 5-6 months in cold storage.
Short-term storage: For storage up to 2-3 weeks, a temperature of-12.8°C
with relative humidity of 60-70% is sufficient. Hatching eggs up to 10 days
can also be stored under these conditions.
A combination of any 2 compatible methods is preferred to a single one,

299
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Shell eggs

Shell eggs
i
Candling (removing the unfit eggs)
I
Removal of egg contents
I
Inspection of egg meats by sight and smell
I
Separation of yolks and whites when desired
I
Mixing and churning of yolks of whites when desired
si

Straining to remove chalazas and pieces of shell and membrane

I
Addition of sugar, salt or other ingredients
si

Pasteurization
I
Freezing and drying of the product

Fig. 41. Frozen egg

Contents of egg

Fresh egg (cold storage for 24 hr at 3-5°C)

i
Candling and inspection
si

Cleaning in detergent sanitizer solution for 5 min.

(water temperature 37.5°C containing 200-500 ppm chlorine)
si

Draining and drying the eggs

I
Separation of egg contents
si

Blending and Alteration

!
Addition of conditioners
(sugar, salt, etc. 10-15% and 0.05% pepsin)
to prevent gelation of the product
i
Pasteurization
1
Packing in metal cans
si

Freezing at -20°C
si

Storage (frozen)

Fig. 42. Frozen egg powder (Source: Tandon, 1973)

300
 EGGS

e.g. oiling of thermostabilized eggs. Oil treatment combined with cold stor¬
age is also done.
Lime water method is best under village conditions, the next is oiling
and thermostabilization. When large number of eggs are to be preserved in
a central place, cold storage is ideal.

PROCESSING OF EGGS

Processing refers to removing the contents of eggs from their shells, produc¬
ing products such as liquid whole eggs, liquid yolks, liquid albumin and
then processed into frozen eggs (Fig.41), egg powder (Fig.42) and egg solids
(Fig. 43).

Spray dried whole egg

Fresh eggs
1
Cold storage (maintained at 4-5°C)
I
Candling and inspection
(candling room preferably maintained at 15°C)
I
Cleaning in detergent-sanitizer solution
(2% sodium hydrochloride solution, water temperature 40°C for 8 min.)
1
Breaking and collection
(steam sterilized, examination of egg contents)
I
Churning and filteration
(homogenized for 5 min. without beating air into egg mass, then filter)
i
Pasteurization (place heat exchanger, at 62.5°C for 3-5 min.)
destroys Salmonella and other organisms
I
Desugaring (0.5% yeast, fermentation at 30°C for IV2 hr)
I
Repasteurization (62.5°C for 3-5 min. to reduce bacterial load and to kill yeasts)
'l'
Spray drying (air inlet temperature 185°C and outlet temperature 85°C,
moisture content 1.5% in dried powder)
I
Redrying (in a vacuum shelf drier at 60°C for 2 hr, vacuum not less than 27.5 mm Hg.
Moisture content 2% (max.) in finished product)
si
Packing (in a tin container with inert gas)
>1
Stored (shelf-life of egg powder 14 to 21 months)

Fig. 43. Manufacture of whole egg powder

301
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

While processing, the following precautions must be taken.

1. Functional properties are not much altered
2. Baking quality is not changed
3. Mayonnaise prepared from frozen whole eggs is more stable
4. Volume of sponge cake is not affected
5. Frozen eggs are more uniform than shell eggs
6. Undergo less deterioration in quality
7. Occupy less space under storage
The basic operations performed in producing commercial egg products
are as follows (Sreenivasaiah, 1982).

Dried eggs/egg solids/egg powder

After pasteurization of liquid eggs, they are used to produce dried eggs
by 2 methods.
Spray method: This method employs milk driers slightly modified for dry¬
ing eggs. The liquid egg or yolk is delivered to the spray nozzle under high
pressure (126.55-351.53 kg/cm2) and the drier temperature ranges from
110°-148.9°C. The moisture content of the product is reduced to 3-5% in
the drying process.
Pan method: Freshly prepared albumin is used. Clarified albumin is poured
into shallow pans which are placed in drying rooms at a temperature of
45.6-47.8°C and the albumin is dried into flake albumin.

Advantages of dried eggs

The dried eggs occupy less space and do not require refrigeration for
storage. These eggs require no defrosting before use and are quite suitable
for various food preparations.
Dried whole eggs and yolks should be vacuum packed. Manufacture of
whole egg powder is given in Fig.43.

By-products
Albumin flakes and egg shell meal are the two common by-products of
processing eggs.

Functions of eggs in cookery

The egg proteins coagulate on heating. The coagulation of proteins is
accompanied by binding of moisture and increase in viscosity. Therefore,
eggs can be used as thickening agents in food preparation. Egg custard is a
good example of this property of eggs.
The egg proteins coagulate between 65 and 70°C and help to hold the
shape of the product in which these are used. Eggs are therefore useful as
binding agents in cutlets, chops, fried and fish.
Eggs, when beaten, form elastic films, which can trap air. This air ex¬
pands during baking, and gives fluffy, spongy product. Thus eggs are used

302
 EGGS

extensively as leavening agents in baked products such as cakes and muffins.

Besides proteins, eggs contain phospholipids such as lecithin, which
are known for their emulsifying quality. Hence the egg as an excellent emul¬
sifying agent in products such as mayonnaise.

Common methods of cooking eggs

Boiling: Eggs are to be heated at a simmering (at about 100°C) to avoid
toughening of protein. A standard hard-cooked egg is tender, the well-cen¬
tred yolk is completely coagulated, and there is no ferrous sulphidering
surrounding the yolk (Margeret, 1968).
Soft cooked eggs are also prepared in simmering water to promote ten¬
derness of the product. The white should be firm but tender, the yolk slightly
thickened, yet not firm at the edges.
Frying: A favourite breakfast item. A high-quality egg should be used
with controlled low heat.
Poaching: These eggs consume no fat. The poached eggs are prepared by
breaking the egg into a bowl and then carefully slipping it into a pan of
simmering water. Directing the egg towards the edge of the pan, as it is
poured into the water, helps to keep the egg from spreading too much in
water. Water should be simmered before the egg is added to minimize spread¬
ing, the water is hot enough to quickly begin coagulating the egg. A well-
prepared poached egg has a firm, tender white surrounding the slightly
thickened, unbroken yolk.
Scrambling: This is an excellent way to serve eggs that are not of very
good quality. Scrambled eggs are customarily prepared by adding a small
amount of milk to dilute the protein and prepare a tender product. Heating
should cease when egg pieces are slightly moist. It should be stirred occa¬
sionally rather than continuously.
Panfrying: Eggs and milk are beaten until they form a homogenous mix¬
ture. When fat is smoking in the pan, the beaten mixture is poured in and
allowed to begin to coagulate undisturbed. The omelette is a continuous
disc of coagulated egg that is slightly moist on the upper surface. A pleasing
brown unbroken exterior and a homogenous yellow-coloured interior are
desired. Controlled low heat produces a tender product.
Baking: Low temperature helps to produce a tender, completely coagu¬
lated white and a slightly thickened yolk.
Thickening agent: Since egg is a good thickening agent, it is used to make
stirred custards, baked custards, cream puddings, pie fillings etc. As egg
proteins coagulate in a product, the entire mixture becomes more viscous.
This property is utilized in preparing these products. Meringues are also
prepared based on this property of eggs.
Foaming: Egg white is a good foaming agent. A foam is defined as bubbles
of gas encaved by thin layers of a liquid. Thick egg whites form stable foams.
Egg whites at room temperature beat quicker and have higher foam volumes.

303
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Hard and soft meringues are simple egg white foams. Fluffy omelettes make
use of egg white foams. Souffles, sponge cakes, angel cakes use egg foams.
Emulsifying agents: The emulsifying properties of eggs are significant in
salad dressings. Cheese souffles, cream puffs, cake batter.

REFERENCES

OTA, Canada, 1961. The production, identification and retention of quality in eggs. Ontario
Department of Agriculture, Canada.
FAO. 2000. FAO Bulletin of Statistics 2000. Food and Agriculture Organization of the United
Nations, Rome.
Kandilkar, Y., Siddiqui, S.M., Reddy, C.V. and Mathur, C.R. 1972. The comparative efficiency
of oil treatment and thermostabilisation on the quality of shell eggs stored at room tem¬
perature. Journal of Food Science and Technology 9(2): 79-82.
Margaret Me Williams. 1968. Food Fundamentals, pp. 217-42. John Wiley & Sons, Inc.,
New York.
Mudami, S.R. and Shalini, R. 1993. Food Science, pp. 126-30. Wiley Eastern Limited, New
Delhi.
Siddiqui, S.M. 1975. A Review: Recent researches in India on the preservation of shell eggs.
The Indian Poultry Gazette 59(4): 90-93.
Sreenivasaiah, P.V. and Siddiqui, S.M. 1982. Preservation of shell eggs. Poultry Guide 19(12):
73-78.
Tandon, H.P. 1973. Egg and its care. Directorate of Extension, Ministry of Agriculture, Gov¬
ernment of India, New Delhi.

LEARNER’S EXERCISE

1. Explain the uses of eggs in food preparations and discuss the changes that occur in eggs
on storage.
2. What points do you remember while selecting the eggs and how do you cook them?
3. Why is egg called a highly nutritious food? List its uses in cooking.
4. Discuss the role of eggs in cooking as a binding, foaming and emulsifying agent.
5. Explain the nutritional contribution of eggs and uses of egg in food preparation. What
are the tests to identify fresh egg?
6. What are the sources of contamination of egg and describe the methods of preservation
of egg?
7. Explain the parts of hen’s egg with the help of a neat diagram.
8. Write in detail about the nutritive value of egg.

304
 Meat, poultry
and fish

M eat is rich in most of the nutrients required by man. This is to be

expected since the tissues and body fluids of man are very similar to
those of animals. Meat is rich in protein and contains all the essential amino
acids. It is also rich in minerals and vitamins. Phosphorous, copper and
iron are present in significant amounts in meat. Of particular interest is the
quantity of iron and copper contained in liver. Thiamine, riboflavin and
niacin occur in good amounts in all meats. Liver usually contains a useful
amount of vitamin A. There are different types of meat derived from different
animals.

TYPES OF MEAT

Beef: Various terms are used to designate meat from different types of
cattle. Veal is the meat from cattle slaughtered 3-4 weeks after birth. The
carcass of 14-52 weeks cattle is classified as calf. Beef is the term applied to
meat of cattle over one year old. Beef carcass is classified according to the
sex, age and sexual conditions of the animals as:
Stear: A bovine male animal castrated at very young age
Heifer: A female bovine animal that has not borne a calf
Cow: A female bovine animal that has borne calf
Stag: A male bovine animal that is castrated after maturing
Calf: A male or female bovine animal up to 12 months of age, generally
from 3 to 8 months of age.
The quality of meat from stear and heifer is the same if the animals are
of the same grade. The quality of meat from cow and bull depends on matu¬
rity, but is generally inferior to that of stear and heifer. The quality of meat
from stag varies depending on the age at which animal is castrated
(Shakunthala and Shadaksharaswamy, 1987).
Mutton: Sheep carcasses are classified under three main classes, based
largely on the age of the animal.
Lamb: This term is used to represent the flesh of young and ovine ani¬
mals of both sexes whose age is 12 months or less. Lamb carcass is distin¬
guished from its smaller and lighter bones, lighter coloured flesh and softer
and whiter external and internal fats. The usual test for lamb carcass is the
break joint of the foreleg. When feet is broken off sharply, the break shows
four distinct ridges that appear smooth, moist and red with blood.
Yearling mutton: Carcasses of young sheep usually from 12 to about 20

305
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

months old are termed yearling mutton. Such carcasses are distinguished
from lamb carcasses by harder and whiter bones, darker and somewhat
coarser flesh and thicker external and internal fat. The break joint of the
foreleg usually breaks in ridges similar in shape to a lamb joint but the
surface is rough, porous, dry and lacks redness.
Mature mutton: This is the flesh of both the males (castrated and
uncastrated) and females of the bovine species that are 20 months age at
the time of slaughter. The colour of the mutton ranges from light to dark
red. The break joint fails to break due to hardening and ossification of bones.
Pork: Pork is the meat of swine. Good-quality pork is obtained from
animals of 3 to 12 months age before the amount of fat becomes excessive.
Pork is not differentiated based on age and sex of swine. Generally pork has
more fat than other meats. Because of this, pork is tender cut of meat. The
young lean pork is highly pink and changes to rose colour as the animal
matures. Bacon is the cut from the belly portion of hog carcass and has a
high percentage of fat.
Organ meats: These include liver, kidney, heart, sweet bread (thymus
and pancreas), brain, lung, tripe (first and second stomach of the rumi¬
nants), head and tail of the animal. Organ meats are less expensive and
more nutritive. Cooking methods vary according to tenderness.
Sausages: These are made of ground or minced meat. Mostly cured meat
and to a lesser extent, uncured meat are used for this purpose. There are
large number of sausage varieties of sausages marketed under different
classes depending on whether the ground meat is fresh or cured, and whether
the sausage is cooked or uncooked, smoked or unsmoked, and dried or not
during manufacture. The cooked and smoked sausages are known as table-
ready meats.
Sausages are enclosed in casings. Normal casings are made from the
animal intestine. As natural casings are expensive, non uniform artificial
casings made of film plastic are used now.

NUTRITIONAL COMPOSITION

Meat contains 15-20% proteins of outstanding nutritive value. The lean

meat contains 20-22% proteins. Of the total nitrogen content of meat, ap¬
proximately 95% is protein and 5% is smaller peptides and amino acids.
The amino acid make up of meat proteins is very good for the maintenance
and growth of human tissue.
The fat content of meat varies from 5 to 40% with the type, breed, feed
and age of the animal. When the animal is well fed, fat deposits subcutane¬
ously as a protective layer around the organs.
Meat fats are rich in saturated fatty acids and it is likely that it pro¬
duces certain forms of atherosclerosis. The cholesterol content of meat is 75

306
 MEAT, POULTRY AND FISH

mg for 100 g. The lean portion of meat contains greater proportions of

phospholipids (0.5-1.0%) and the fatty acids in this lean portion have higher
proportion of unsaturated fatty acids than tissue fats.
In meat carbohydrates are found in very small quantities in the form of
glycogen and glucose. Meat is an excellent source of some of the vitamins of
the B complex and a good source of iron and phosphorus. Meat also con¬
tains sodium and potassium. The vitamins and minerals are found in the
lean portion of the meat. Meat contains the protein-hydrolyzing enzymes,
cathepsins, and these are responsible for the increased tenderness of meat
during ageing.
The colour of meat is primarily due to myoglobin. Variations in colour of
meat depend on the chemical state of myoglobin. Meats cured with nitrates
remain pink as nitric oxide myoglobin is stable. Haemoglobin also contrib¬
utes to the colour of meat to some extent.

METHODS OF SLAUGHTER

Slaughtering techniques
Slaughtering means putting the food animals to death and thereafter
prepare the carcases for human consumption. Methods of slaughter should
thus be aimed at complete bleeding as far as possible and least unneces¬
sary suffering and minimum struggling to the animal. For good bleeding,
more than half of the blood must drain out at the time of slaughter which
determines the keeping quality of meat. In some countries, however, stun¬
ning of the animals prior to slaughter is now mandatory for human consid¬
erations.
It is considered that for efficient bleeding, the heart and respiration of
the animal must remain in function after slaughter for as long as possible.
It is believed that animals stunned before slaughter bleed more per¬
fectly, although colour of the meat from ritualistically slaughtered animals,
without stunning, may remain more pale, due to retention of more oxygen
in the blood.
However, there are some socio-religious prejudices among different meat-
eating communities of the world about the method of slaughter of food ani¬
mals. There are other described as Hindu or Sikh (jhatka), Muslim (halalj
and Jewish methods. Animals are thus slaughtered either after prior stun¬
ning or without stunning. For stunning there are various methods such as
stab or blow at the back of neck, pithing (puncturing at the back of neck),
use of captive bolt, electrical and chemical etc. (Joshi, 1994).
Generally in cattle, stunning is done with a captive bolt and thereafter
pithing is done by inserting a rod through the aperture of captive bolt to
destroy the medulla to prevent reflex muscular activity at the time of dress¬
ing of the carcase.

307
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Cattle, sheep and goat are slaughtered by cutting the animal’s throat;
severing the larger vessels in the anterior thorax such as jugular vein, ca¬
rotid artery, anterior aorta and anterior vena cava (Mohmeddon method). It
does not severe the spinal cord and medulla, thus ensures efficient bleeding
and is universally adopted method of bleeding, in the Western countries.
Neck stab method of slaughter using a double-edged knife pierced at
the back of the neck (nape) at atlanto-occipital space, to severe the medulla
is in vogue in South America. Thereafter large vessels of throat are cut
(carotid, throat vein and oesophagus). It is followed for reindeer processing
also.
According to Hindu mythology slaughter comprises severing the neck of
the animal at one stroke as close to the head as possible, with a single blow
of a sharp-edged heavy instrument. It also includes ritualistic slaughter.
This method is said to be inferior as far as the efficacy of bleeding is con¬
cerned. The animal is allowed to bleed for 2-10 min. but does not ensure
efficient bleeding.
Jewish slaughter regulations are very old (500 ad) in which slaughter is
done without previous stunning. This method of slaughter is called schechita
and is done with the help of jewish slaughter knife known as shocket. Such
meat is designated as koscher meat. The neck of animal including skin,
muscles, oesophagus, trachea carotid and jugular vein are severed in this
method (pig is prohibited for human consumption and jewish code probably
because of trichinosis and cysticerocosis).
Pigs are slaughtered by knifing along the middle line of neck at the
depression, in front of sternum, severing the vena cava and a corotid artery.
In sheep and goats, after the incision, head is jerked back to severe the
spinal cord near the brain.
In pithing, neck is punctured by knife, pierced between the first cervical
vertebra and occipital bone to damage the medulla. It renders the animal
motionless at the time of bleeding and also unconsciousness.
Animals before slaughter are stunned to render them unconscious ei¬
ther with a striking instrument (club or maul), striking at the roof of skull
(cattle and horse—at a point intersecting the lines drawn from the base of
horns on one side to the inner canthus of the eye on the other side; sheep
and goat—at the back of the neck; pigs—unsuitable due to stout skull bones,
it is also used in poultry). Pole axe is also used for stunning at the same spot
as for the club, which drives into the cerebrum of the animal, destroys it
and renders the animal unconscious.
In addition to these, striking instruments of different kinds using a bolt
driven into the brain of the animal by spring action or pistol discharging a
free bullet or a bolt (captive bolt instrument) are also used for stunning,
prior to slaughter. But it may sometimes fail to produce desired result and
may cause gushing of blood, and thus have been replaced by superior tech¬
niques such as electrical and chemical stunning used in modern abattoirs.

308
 MEAT, POULTRY AND FISH

METHODS OF INCREASING TENDERNESS OF MEAT

The methods commonly used for increasing the tenderness of meat are
(z) conditioning or ageing, (iz) mechanical alteration of meat, (ziz) cutting the
meat before it is chilled and before rigor mortis has set in, (iv) treatment
with proteolytic enzymes, (v) freezing, {vi\ change in pH, (vii) cooking and
(viii) addition of acid, salts, and sugar before cooking.

Conditioning or ageing
Conditioning of the meat at 0°C for 48 hr is the method commonly used
for tenderizing meat.

Mechanical alteration
Mincing, grinding or pounding of meat helps to break the muscle fibres
and connective tissue and results in increased tenderness in meat.

Treatment with proteolytic enzymes (artificial tenderizing)

Methods used are (z) injecting enzyme into the animal before slaughter,
(z'z) introducing enzymes through fork holes into meat before cooking and
(zzz) freeze drying the meat and rehydrating with water containing proteolytic
enzymes before cooking. The injection of proteolytic enzymes (fungal protease,
papain, bromelin and tiypsin) into animals one hr before slaughtering results
in marked tenderness in meat. Introducing proteolytic enzymes into meat
through fork holes before cooking has been found to bring about marked
increase in tenderness in meat. Freeze drying meat and rehydrating it in
water containing proteolytic enzymes proved effective in tenderizing meat.

Freezing
Meat is conditioned by keeping at 0°C for 24 hr and preserved by freez¬
ing. Tenderness of meat is increased.

Changes in pH
Several workers have found that when solutions of lactic acid or ammo¬
nia were injected into meat cuts and the cuts stored at 0°C for 4 days, the
cuts having pH 5.0-6.0 were the least tender whereas the meat cuts having
pH 4.0 or 7.0 were quite tender.

Cooking
The effect of cooking depends on the balance between the extent of
softening of collagen and hardening the muscle fibres. The effect of cooking
also depends to a great extent on the content of connective tissue of the
meat, the degree of doneness, the temperature at which meat is cooked and
the rate of cooking. As cooking proceeds, protoplasmic proteins of the muscle
fibres begin to coagulate and become tougher, while the connective tissue
break down to gelatin.

309
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Acid
There is not sufficient time for organic acids to penetrate into meat in
ordinary cooking periods. Among factors affecting penetration of added or¬
ganic acids into meat are size of the meat piece, degree of postmortem changes
in the meat and the molecular weight of acid.

Mineral salts
Addition of sodium chloride or sodium and potassium phosphate in¬
creases tenderness of meat. Meat soaked in a mixture of mono-and
dihydrogen sodium phosphates with pH 6.0 has been found to increase in
its tenderness after braising.

MEAT COOKING

The two basic types of meat cooking are dry and moist dry methods.

Dry-heat methods
Roasting: This is done by the constant-oven-temperature method. The
oven thermostat should be set at 148.9°-162.8°C. This temperature pro¬
motes retention of juices and also easy oven-cleaning due to less splattening/
burning than high oven temperature. Oven roasts carve better if removed
20 min. before serving.
Broiling: This uses direct heat. It is suitable for tender meats, which are
at least 2.54 cm thick. Meat should be broiled on a specially designed pan
that allows fat to collect in a tray beneath the meat rack.
Panfrying: In this method fat is added to the skillet to prevent meat
from sticking. It is necessary to turn the meat occasionally to develop an
even colour on the meat, but turning should be kept to a minimum. High
temperature should be avoided, as it breaks the fat into a product called
Acrolein which not only impairs meat flavour but also causes smarting of
the eyes.
Deep fat-frying: This method is well suited to quick preparation of chicken
fryers and fish. Temperature should be controlled at 148.9°-176.7°C as high
temperature causes smoking and also leaves meat undone in the middle
while imparting a pleasant colour outside. Too low a temperature will lengthen
frying time and result in a greasy product.
Moist-heat methods: These methods are used for less tender cuts of meat.
The combination of moisture, heat and a long preparation time causes the
meat to become more tender as gelatin is gradually formed from collagen.
Braising: Braising is a popular method in which meat is first carefully
but thoroughly browned on all sides. Then a small amount of liquid is added
and the meat is tightly covered for a long time till it becomes tender. The
liquid is maintained at simmering temperature. The relatively low tempera¬
ture prevents toughening of meat but permits conversion of the connective

310
 MEAT, POULTRY AND FISH

tissue. Though water is commonly used as the liquid, many flavours may be
introduced e.g. soup concentrates. Tomatoes and lemon juices may also be
used and they hydrolyze the protein because of their acidity.
Stewing: Stewing, boiling and cooking are terms used for the same proc¬
ess. Stewed meats are browned as the initial step in preparation. Then a
large amount of water is added and the meat is simmered until tender.

Changes produced in meat during cooking

Meat is cooked to destroy any harmful microorganisms present in it
and to improve its palatability. The changes brought about in meat are
change in colour, weight, volume, flavour, fatty tissue and physical changes
in the structural proteins, changes in the connective tissue, and muscle
fibre.
Change in colour: The change in colour during cooking is due to dena-
turation of myoglobin and is converted to brown or dull red globin haemo
chromogen. At the same time, some of the myoglobin is oxidized to
metamyoglobin which has a brown colour. Iron is in the ferric state in
metmyoglobin. Hence cooked meat assumes a dull red to brown colour.
Shrinkage in volume and weight: The temperature of cooking affects both
the rate and extent of shrinkage resulted in loss of volume. The pH of the
meat seems to be most important factor in determining the loss in cooking.
The shrinkage is greatest if the meat has a pH of 5.8, i.e. the isoelectric
point of the main protein of muscle. The shrinkage is less at pH 4.0 or 7.0.
Changes in fatty tissue: The changes in fatty tissue take place due to
breakdown of collegenous tissue and escape of melted fat. The surface brown¬
ing of fat may be due to oxidation of fat. The amount of fat found in drip
varies depending on the fat content of meat.
Changes in connective tissue: The connective tissue contains about 62%
water, 32% collagen and 1.6% elastin. Collagen is converted into soluble
gelatin during cooking of meat. The gelatin gets dissolved in the water used
for cooking. Elastin does not undergo any change during cooking.
Changes in intracellular proteins and muscle fibres: The protoplasmic
proteins found in muscle are denatured and become insoluble in water. The
diameter and length of muscle fibre shrink.
Flavour: The odour and taste of cooked meat arise from water and fat-
soluble substances present in raw meat and by the liberation of volatiles
formed during cooking. Water extract of raw meat develops a meaty flavour
on heating. It is, however, weaker than the flavour of water in which meat is
cooked. Some Japanese workers in 1956 reported that mono-nucleotides
(inosine-5 mono-phosphate) are substantially responsible for the flavour of
meat during cooking. The volatiles of cooked meat contain H2S, ammonia,
acetaldehyde, acetone and diacetyl.
Juiciness: Juiciness depends on ability of meat proteins to retain the
cooked water. The juiciness of cooked meat is greater at pH 4.0 or 7.0 than
at pH 5.8. The damage in juiceness is correlated to shrinkage in cooking.
311
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

nn
OULTRY

Various types of birds like the chicken, turkey, goose, duck are included in
this group. Poultry is one of the sources of animal proteins in our diet.
Poultry is sold in various forms-—whole live birds, or dressed as whole (Fig. 44).
Various cuts of poultry fresh or frozen are also available. Younger birds are
more tender than mature ones. The young bird has a soft skin, which can
be separated easily from the flesh. The breast bone and other bones of
young birds are tender and can be removed easily. Classification of poultry
is given in Table 35.

Table 35. Classification of poultry

Name Age

Chicken
Broiler or fryer 9-12 weeks
Rooster 3-5 months
Capon < 8 months
Hen 5-7 weeks
Stewing chicken Mature female
Cock Mature male

Turkey
Fryer roaster <16 weeks
Young hen 5-7 months (female)
Young tom 5-7 months (male)
Old turkey 15 months (mature)

Ducks Small ducklings

Geese Young bird

Fig 44. Poultry chicken

Poultry cooking
Raw chicken has little or no flavour; it develops during cooking. The
principles of cooking poultry are basically the same as for cooking meats.
The cooking method is selected on the basis of the tenderness of the poultry'
and its fat content, both influenced mainly by the age of the bird. Moist heat
 MEAT, POULTRY AND FISH

methods are applied to older and tougher birds to make them tender and
palatable. Dry heat methods are applied to young tender birds.
The changes that take place during the cooking of poultry are similar to
those of other meats. To obtain tender, juicy and uniformly cooked poultry,
low to moderate heat is to be used. Intense heat results in the toughening of
proteins, shrinkage and loss of juiciness.
Broiling and frying: Young tender poultry is cooked by broiling, frying,
baking and roasting. For broiling, the bird is placed in the broiler with the
skin side down. The whole bird or halves may be broiled. The broiler is
placed about 10 cm from the flame or heating element and cooked at a
broiling temperature of 177°C till the internal temperature of the breast
muscle reaches 95°C (about 45-60 min.). Because of the low fat content of
the young birds, basting with melted fat will improve the flavour, payabil¬
ity and appearance of the preparation.
Frying and deep fat frying are particularly suitable for cooking low-fat,
young, tender poultry and more frequently used than broiling. The halves of
the birds are frequently fried. Before frying they are coated with seasoned
flour or beaten eggs and bread crumbs. They are then carefully cooked to
prevent overbrowning before the meat is tender. If deep-fat-fried, the bird
must be steamed until the stage of doneness before being dipped in flour or
in egg and crumbs, and fried slowly. The time required for browning in deep
fat is too short to promote thorough cooking of meat (Shakunthala and
Shadaksharaswamy, 1987).
Roasting: Poultry may be roasted, stuffed or unstuffed. When the whole
bird is roasted, tender parts, such as the breast may be overcooked before
the legs and thighs are cooked to the desired state. For stuffed birds, roast¬
ing should be continued till the internal temperature of the stuffing reaches
74°C. This eliminates the possibilities of bacterial food poisoning. When the
poultry is roasted without stuffing, it is cooked at an oven temperature of
163°C till the internal temperature of the thigh muscle reaches 85°C.
Tandoor chicken: This is a well-known and popular Indian chicken dish.
This is bar-be-cued chicken. The cooking is done in a clay oven called a
tandoor. It is a long earthenware pot embedded in clay and earth. Charcoal
is put inside and the oven is made red hot. Other types of ovens are de¬
signed and used. Tandoor chicken, either whole or cut, is used. The skin is
removed from the chicken and the flesh pricked with a fork and sprinkled
with salt. Tandoor sauce is then smeared on the chicken which is then left
aside for 6-8 hr. It is then cooked in the tandoor. Half way through the
cooking time it is removed from the oven and brushed all over nicely with
butter or oil and cooked again until the chicken is fork tender. Chicken
cooked this way is delicious.
Braising and stewing: The older tougher birds are cooked this way. Dis¬
jointed pieces of chicken are generally braised. Generally, they are First
browned by frying after which water is added and the bird simmered until it

313
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

is tender. For stewing, the whole bird or cut pieces are used. They are cooked
in water with seasonings and vegetables till they are tender.

PRESERVATION METHODS FOR MEAT AND POULTRY

Refrigeration
Chilling: The dressed poultry is chilled using ice and held at 3°C. This
extends the life of edible meat by discouraging microbial growth, which oth¬
erwise becomes spoiled in 1-3 days. Muscle is attacked by proteolytic enzymes
and free amino acids rise. Intracellular osmotic pressure increases and water¬
holding capacity becomes greater. This increases tenderness. Residual gly¬
cogen is brokendown to glucose by amylolysis. Free sugars, amino acids
and hypoxanthine together contribute to strong meaty flavour.
Freezing
The dressed poultry is packed in polythene bags and frozen at -40°F
(-4.04°C) and held at -23.3°C. When meat is frozen, chemical changes de¬
pend on the rate of freezing, temperature reached and duration of frozen
storage. A major effect is the drip, a reddish exudation on thawing due to
damage to muscle proteins, which reduces water-holding capacity. Slow
freezing can lead to loss of nutrients. Low temperature inhibits and long
storage enhances undesirable changes in fat and protein.

Thermal processing cooking

The effects of heat are progressive with time and temperature. There is
a loss of water-holding capacity. There is a denaturation of protein. Exces¬
sive heating may cause breakdown of amino acids and yields hydrogen sul¬
phide and ammonia.
Canning: The poultry meat is cut and cooked in the usual way for 30
min. It is transferred to heated sterilized cans at 100°C. Steam exhausted at
100°C for 30 min. double seamed and sterilized by cooking in steam under
6.35 kg pressure at -3.9°C for 60 min. (Swaminathan, 1987).
Commercially canned meats are sterile as they are-processed to a point
(3 min. at 121°C) at which most organisms, especially Clostridium botulinum
and its spores are killed. Denaturation, amino acid destruction, H2S libera¬
tion, met myoglobin formation, collagen solubilization, maillard-type browning
and accompanying flavour changes are more marked in canning than in
normal cooking (Varadarajulu, 1973).

Drying
Dehydration: Drying prolongs life but adversely affects meat. Loss of
water causes closer packing of muscle fibres, denaturation on the fiber sur¬
face which opposes re-entry of water. For long-term storage, dehydrated
meat must be packed to exclude as much moisture and oxygen as possible.
Non-oxidative deterioration causes a bitter flavour and brown discolouration.
This can be minimized by drying the meat to a very low moisture content.

314
 MEAT, POULTRY AND FISH

Freeze-drying
Drying meat by sublimation of the water from the frozen state is accel¬
erated freeze-drying. In the accelerated freeze-drying, ice sublimes from the
frozen meat under high vacuum, the moisture content reducing to 2% within
4 hr. Because of low temperature and high speed of operation, the water¬
holding capacity is unaffected. With an increase in time and temperature of
storage, the concentration of brown oxidation form of myoglobin increases.

Curing and smoking

Curing: In curing, the additives, salt or sugar owe their efficacy to their
osmotic action which deprives microorganisms the available moisture. Ini¬
tially there is an osmotic removal of water from the muscle proteins by
25-30% solution of sodium chloride. The final concentration of NaCl at¬
tained is 4-5%. Salt inactivates lipoxidase of muscle, because curing causes
an acceleration of oxidative rancidity in the fat. In brines used for curing,
2.5-4% of potassium or sodium nitrate is included for its beneficial action
on colour, although nitrate has a specific anti-microbial action specially in
acid solution. A limit of 200 ppm is set by regulation for nitrites as it is toxic
at higher levels mainly through its effect on blood pigments. Salt improves
water-holding capacity (Chatterjee et al., 1971).
Smoking: It is an additional process which enhances meat preservation.
Smoke contains phenols (derived from decomposition of lignin) which have
anti-microbial action, specially enhanced by the drying action of the smok¬
ing process. Smoking also delays fat rancidity. The flavour of the smoked
product depends partly on the reaction between the phenols and polyphenols
with the SH groups in protein and between carbonyls and amino groups
(Draudt, 1963).

Chemical preservation
Addition of chemicals such as antibiotics, chlorine, nitrates or nitrites,
polyphosphates, edible organic acids like sorbic, succinic and lactic acids
aid preservation of poultry meat.

Ionizing radiation (beta or gamma)

The efficacy of using this is achieved through considerable depth of the
product even after packing, with little rise in temperature and usually little
total chemical change.

Pickles
Preparation of pickle using poultry and meat is given in Fig.45. Pickling
is practised as a means of preservation. In the pickling process, the pickling
mixture is used. During pickling by salts, the high osmatic pressure of the
external fluid initially draws water and soluble proteins out of the meat.
Later, salt diffuses into the meat and binds to the proteins, causing some
expelled protein to diffuse back in. This causes a swelling of the meat. The

315
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

salt protein complex that forms binds water well (Shakunthala and
Shadaksharaswamy, 1987).

Ingredients (spices) used for pickle

Poultry meat with bone 5 kg

Common salt 220 g
Sodium nitrite 1 9
Monosodium glutamate 5g
Vinegar 1.5 litres
Red chilli powder 75 g
Garlic 30 g
Black pepper 30 g
Cumin 15 g
Clove 5g
Cinnamon 5g
Refined mustard oil 500 ml

A B

Dressed chicken (cut-up parts) Condiment and spices*

ground by adding vinegar
i i
Chilled overnight (2CC) Fried in mustard oil
(left after use in ‘A’)
1 i
Cleaned with vinegar, smeared Remaining quantities of
with salt and pepper ingredients added
1 1
Roasted in mustard oil Cooked at 165°C for 10 min.
(165°C for 15 min.)
I
Cooled and cut into pieces Pickle stored in sterile
screw cap bottles

Fig. 45. Pickling of poultry and meat

PROCESSING OF MEAT

The various important processed meat products are canned meat,

smoked meat, sausages and dehydrated meat (Swaminathan, 1987).

Canned meat
The meat is cooked and filled in the can along with the gravy, leaving a
little head space. The can with the lid loosely fixed on, is placed in a vacuum
chamber where the final operation of double seaming is completed. The
sealed can is heat processed at 121°C in an autoclave for 60 min. to destroy
microorganisms. The can is cooled by dipping in cold water. Adequate heat

316
 MEAT, POULTRY AND FISH

processing is essential to ensure that pathogenic organisms, if present are

completely destroyed.

Cured meat
Meat is pickled by the use of curing agents. The approved curing agents
are sodium chloride, sodium nitrate, sodium nitrite and vinegar. Refriger¬
ated conditions at 30°-4.4°C is needed for curing. The curing agents in the
pickle mixture are as follows:
Sodium chloride : 14-24%
Sodium nitrate : 0.1-0.25%
Sodium nitrite : 0.1-0.15%
The meat is covered with pickle mixture and kept at 4.4°C for 15-20
days.

Smoked meat
Smoking helps preserve the meat and develop flavours in it. Wood smoke
contains small amounts of formaldehyde (25-50 ppm), higher aldehydes
(140-180 ppm), formic acid (90-125 ppm), acetic and higher ends (460-500
ppm), phenols (20-30 ppm), ketones (190-200 ppm) and resins (1,000 ppm).
These compounds have antiseptic properties and destroy microorganisms
present. The temperature and period of smoking vary with the type of meat.
Bacon receives a smoke treatment for 18-24 hr at temperatures of 50°-55°C.
In case of sausages, the smoking is done for a few hours. After smoking the
material is packed in polythene bags and kept at refrigerated conditions
(Bartley, 1959).

Sausages
Sausages usually consist of cooked chopped meat ground to a paste
with seasonings and packed in casings. Sausages are classified into six
groups, viz. fresh, smoked, cooked, cooked and smoked, semi-diy and dry.
Meat is the main ingredient. A limited amount of cereal or potato flour is
used in certain types of sausages. The method of preparation is as follows.
Meat is mashed into fine paste. Curing agents are added to the mashed
meat and mixed well. Salt (2.5% level) and spices (1% level) are added and
mixed well. The blend is stuffed into sheep casing. The sausages are linked
by twisting into pieces of 6.35 cm length. They are cooked at an internal
temperature of 65°C, cooled in water at room temperature. Alternately, sau¬
sage can be smoked for 30 min. before it is cooked, if a smoked sausage is
desired. Smoking develops special flavour in the product. The individual
pieces are separated, packed in polythene bags and stored, under refriger¬
ated conditions.

Dehydrated meat
The meat is cut into pieces and cooked in steam for 30 min. at 4.53 kg
pressure. The cooked meat is passed through a meat chopper and the

317
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

chopped meat dried in a continuous rotary drier. The temperature of incom¬

ing air is 65.6°-71.1°C and drying takes about 3 hr. The moisture content of
dried meat is about 4-5%. The dried meat is compressed and packed in
cans (Margaret and Williams, 1968).

Strained baby foods based on meat

Strained baby foods containing meat are being manufactured and used
in large quantities in USA and Europe for feeding infants. Meat is cooked,
minced and ground before canning.
Strained meat preparations have been included in the diets of infants
at 5-6 months of age.

PROCESSING OF POULTRY

Chilling in slushed ice

The dressed poultry is chilled using ice and held at 3°C. It keeps well for
about 9 days at this temperature.

Freezing
Dressed poultry is packed in polythene bags and frozen at -4.4°C and
held at -23.3°C. The frozen poultry can be kept for about 6 months in good
condition.

Canning
The poultry meat is cut and cooked in the usual way for 30 min. It is
transferred to heated sterilized cans at 100°C, steam exhausted at 100°C
for 30 min. double seamed and sterilized by cooking in steam under 6.35 kg
pressure at 121.1 °C for 60 min.

Sausages
Sausages from poultry meat can be prepared in the same way as those
from meats described earlier.

Dehydration
Poultry meat can be dehydrated in the same way as meat.

Canning of fried chicken

Chicken meat chunks are fried in fat and ground condiment paste is
added. The fried material is packed in cans, double seamed and sterilized at
6.35 kg steam pressure for 60 min.

Cured and smoked poultry

Cured and smoked poultry can be prepared in the same way as cured
and smoked meat described earlier.

318
 MEAT, POULTRY AND FISH

FISH

Fish may be grouped broadly into fin fish and shell fish. The term fin fish
refers to fishes having bony skeleton, while the term shell fish to mollusks
and crustaceans having shells. These fish and shell fish are very good sources
of animal proteins, minerals and vitamins.

Nutritional composition
Fish are an excellent source of protein. Fat content of the fish varies
from 0.2 to 20% depending on the species and season of the year. Most of
the fish have low fat content. The fat content of the herring may range from
8- 20% and of sardine from 1.9-14.6%. The protein content also varies from
9- 20% depending on the water content of the fish. For example Bombay
duck has a protein content of 9.1% because of high moisture content of the
fish (Mudambi and Shalini Rao, 1993).

Types of seafoods
Flesh foods may be classified into two major categories. Fish (vertebrate)
and shell fish (invertebrate). The former are covered with scales and the
latter with some type of shell. Shell fish are of two groups — the molluscs
and the crustaceans. The molluscs are of soft structure and are either par¬
tially or wholly enclosed in a hard shell that is of largely mineral composition.
Molluscs include oyster, clams and mussels of crustaceans and lobster,
crab, shrimp and cray fish.
The kinds of scaly fish available for food vary widely in different locali¬
ties. They include both salt-water and fresh-water varieties and differ in
flavour and quality depending partly on the water in which they are grown.
Fish from cold, clear and deep waters are superior in quality and in flavour
to fish from warm, muddy and shallow waters. Salt-water fish usually have
a more distinctive flavour than fresh-water one and oily fish have more
flavour than the lean varieties (Osee and Bennion, 1970).
Fish are often classified on the basis of their fat content. Lean fish have
less than 2% fat in their edible flesh, whereas medium-fat fish 2-5% fat.
Most of the fat in such lean or medium fish varieties as cod, haddock, hali¬
but and pallock is in the liver.
Fish are sold in many forms (Fig. 46). Drawn fish have only the entrails
removed. Dressed fish are scaled and eviscerated and usually have the head,
tail and fins removed.

Steaks
Dressed fish is cut into slices from head to tail.

Chunks
Dressed fish is cut into big pieces of chunks down its whole length.

319
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Drawn fish

Fig. 46. Fish and fish cuts

Fillets
Dressed fish is sliced length wise from the backbone. Butterfly fillets
can be made by keeping the outer skin intact which holds both pieces to¬
gether. However some varieties of fish have high fat content. These are mainly
used for the extraction of fish-liver oil, e.g. cod-liver oil, shark-liver oil. Fish-
liver oils are rich in vitamins A and D. Fish contains poly-unsaturated fatty
acids. The fish, which contain 6-20% fat, are called fatty fish. As fish are an
aquatic food, they provide us with iodine. Canned fish are also available,
e.g. canned sardines. Some fish are dried, salted or pickled for further use.
Ready-to-eat fish are also available. These require warming before being
served.
Shell-fish may be marketed in the shell, shucked (removed from the
shell), headless (shrimp and some lobster) and as cooked meat.
Ma^iy convenience items containing frozen fish are now available. These
include frozen, breaded, pre-cooked fish fillets and sticks; frozen, creamed
fish dishes; fish soups; fish pies; and fish dinners.

Selection, handling and cleaning

Some points which must be borne in mind while judging the freshness
of fish are absence of unpleasant odour and sunken eyes. The gills should
be red, tails should be stiff, flesh should be firm and not flabby and scales
should be plentiful.

320
 MEAT, POULTRY AND FISH

Handling and cleaning

The fish catch varies greatly according to season and locality. Some
catches are uniform, but for most of the year trawl catches contain a variety
of species and sizes. Fishing takes up many of the working hours of the
small crew of trawlers and leaving little time for the handling, chilling and
storage of the catch. Mechanical equipment for catch handling has so far
been very limited or non-existent.
When industrial fish (small whole Fish intended for reduction to meal)
are stored in the cold without effective chilling, the atmosphere within the
hold may become dangerous because fish undergoing spoilage emit gases
such as C02, and H2S which accumulate in lower part of the hold. Chilling
of industrial fish is essential not only for security and health reasons but
also for maintaining fish yield and quality. Another problem is handling of
large mixed catches and the grading into industrial fish and food fish. With¬
out mechanical-grading equipment, only a fraction of food fish, mainly the
largest fish, can be retrieved. Thus, at times, substantial quantities of smaller
food fish remain among the industrial catch.
Improved equipment and facilities are required if all these fish are to be
handled, chilled and stored properly for food purposes. The larger fish are
gutted by hand, washed and iced either in bulk or boxes.
The chilling system is that developed by the British White Fish Author¬
ity. The containers, which are heat-insulated, are charged with ice in port
before being lined up on the floor of fish hold. Just before the container is
filled with fish, sea-water is added up to the level of the ice, and the contents
are mixed by the introduction of compressed air at the container bottom.
This circulation is maintained while the container is being filled and until
most of the ice has melted and the fish temperature brought below 0°C. The
container is kept closed as long as the fish temperature remains near 0°C.
Repeated chilling by brief air circulation may be required during extended
storage. The fish are unloaded in the containers, which may serve briefly as
raw material for storage for the filleting industries (Karsten Back Olsen and
Poul Hansen, 1982). Many of the modern shrimp trawlers are equipped
with quick-freeze units, capable of freezing the catch from 20°C to -13°C in
30 min. The cold store operates at -8°C; there is also an insulated storage
area that is some 2°-3°C lower than the ambient temperature.
Pre-storage and storage treatments involve gutting, which is removal of
the head and internal organs; the samples were washed with clean seawater.
The fin fish are treated with ice-in an ice: fish ratio of 1:1. The samples are
stored in boxes in the insulated area adjacent to cold store (Crean, 1982).

Preservation and processing

As fish is a highly perishable commodity, various methods have been
devised to preserve it. Before preservation, fishes are washed with clean
water to remove slime, blood stains, etc. Larger fishes are gutter (i.e. all the

321
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

internal organs or viscera are removed) and the body cavity washed. The
various methods adopted for preservation are drying, salting, smoking, freez¬
ing and canning.
Sun-drying is the most ancient method. Drying removes moisture from
tissues and helps arrest bacterial and enzymatic putrefaction. In India, more
than 35% of the total catch of sea fish is cured under the sun. This method
is not hygienic. There is an appreciable percentage of loss due to putrefac¬
tion and spoilage, and the dried fish develops as peculiar odour.
Salting (pickling) is also widely used in India. The dry-salting or wet¬
salting method is used. In the former method, fishes are first rubbed with
salt powder and then packed in tubs with dry salt powder sprinkled be¬
tween layers of fishes. After about 10-20 hr the fishes are removed, washed
in brine and dried under the sun for 2-3 days.
In wet-salting, cleaned fishes are packed in large vats containing con¬
centrated salt solutions and stirred daily till properly pickled. With large¬
sized fishes, longitudinal slits are made in the flesh to allow penetration of
salt. After pickling for 7-10 days, the salty water that oozes out from the fish
is allowed to drain off. Wet-salted fish is sold without drying. It does not
keep for long and therefore has to be used within 3-4 months. In some
countries fishes soaked in salt solution are taken out and smoked. Smoked
fish is not popular in India.
The above methods employed for curing fish are rather crude and primi¬
tive and the products are unattractive. Case-hardening, rancidity develop¬
ment, colour changes, mold growth and attack by insects and mites are
some of the common defects of fishes cured by sun-drying and salting.
Chemicals, such as acids, sodium benzoate and ethylene oxide and the
antibiotic aureomycin can prolong the life of fish. However, many countries
do not permit the use of these preservatives. Irradiation of fish by y-radia-
tion prolongs their storage life by 20-25 days. But the current methods of
importance for preserving the quality fish are freezing and canning.

Freezing
Freezing can greatly extend the period of storage and is effective in
keeping the fish in a condition similar to that of fresh fish, if the fish is
gutted and frozen down to -29°C within 2 hr of its catch. In some cases
clean whole fish is frozen. Finfish are usually frozen as fillets (length-wise
cuts), steaks (cross-cut section) or sticks (length-wise or cross-wise cut from
fillet or steaks). Large fish are frozen by the sharp freeze, a comparatively
slow freeze. Small fish, fillets and steaks are quick frozen. This type of freez¬
ing gives a better produce. The storage life of quality frozen fish, with a low
fat content, can be as long as two years.
Some undesirable changes can also take place if proper care is not
taken during freezing. Slow freezing can result in protein denaturation. As
the water freezes in the fish, the salt concentration of the muscle tissue

322
 MEAT, POULTRY AND FISH

increases, causing denaturation of the protein, making it tough and rub¬

bery. Another effect of freezing is desiccation or drying. Drying is caused by
the transfer of moisture from the surface of the fish to the cold surface of
the freezing equipment. Frozen fish undergoes oxidative changes, and fatty
fish becomes rancid more quickly than lean ones. Desiccation and oxidation
can be prevented by properly protecting fish with suitable wrappers before
freezing.
Preservation of fish by freezing is not yet widespread in India. Cold-
storage facilities are available in areas where fisheries are highly developed.

Canning
While high-fat fish do not store as well as low fat fish in the frozen state,
oily fish are the most suitable for canning. Salmon, tuna, sardine, herring,
lobster, shrimp, etc. are canned. In case of salmon, tuna, sardine and mack¬
erel additional fish or vegetable oil is commonly added to the fish prior to
can closure; shrimps are canned in brine. Canning retains the natural fla¬
vour of the fish. Large quantities of certain types of fish are canned in this
country mostly for export purposes.
Shellfish become dark or discoloured during canned storage. This is
due to the release of hydrogen sulphide from the sulphur components of the
fish, which reacts with the iron in the can to forme black iron sulphide. This
can be avoided by using an enamel, especially an enamel-containing zinc,
since the zinc sulphide formed is white in colour.

Fish meal
Processing in the form of meal is another method for fish. Fish meal is
prepared from whole fish and is not suitable for human consumption. Two
processes are used, viz. wet process and dry process, depending on the fat
content of fish (Swaminathan, 1987). Wet process is used for fatty fish while
the dry process is used for lean fish. Fish meal on an average contains
55-70% proteins, 2-5% fat, 10-12% minerals, and 6-12% moisture. It is
used in animal and poultry feed.

Wet process
In the wet process the fish such as sardines are cooked to remove the oil
using hydraulic press. Resulting cake is dried in the cabinet drier and pow¬
dered in hammer mill before packing.

Dry process
This process is applicable to fish with low oil content. The entire fish is
cut into pieces, cooked in steam and dried in cabinet drier. The dried mate¬
rial is powdered in a hammer mill and packed in large containers.

323
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Fish protein concentrate

Fish Protein Concentrate (FPC) is the name given to edible fish product
suitable for human consumption prepared from fresh fish. The FPC is odour¬
less, blend powder, usually, of light colour containing very low levels of lipids
(less than 1%). The process of manufacture is described below. The FPC
may be prepared from any eidble fish species or aquatic animal. The fish
must be dressed and gills, entrails and viscera removed before processing.

Processing
The dressed fish is cooked in steam. Water and lipids from the cooked
fish are pressed out in a hydraulic press. The material is dried in a cabinet
drier.

Solvent extraction
Lipids present are removed by solvent extraction. The solvents used are
isopropanol, ethanol and hexane either alone or in combination. The solvents
should confirm to the food-grade standards suggested by Protein Advisory
Group (PAG). The solvent present in the meal should be removed completely.

Powdering and packaging

The material should be powdered and packed hermetically in tins or
suitable containers and protected from contamination with bacteria and
insects and against absorption of moisture. The packed material should be
stored under cold-storage conditions.

Fish liver oils

Fish oils are of two kinds, liver oils and fish body oil. Liver oil is the
natural source of vitamin A and to a lesser extent of vitamin D. Fishes such
as cod, halibut, tuna and shark, are good sources of fish liver oils. The oil
and vitamin A content vaiy in different fishes. Body oil is obtained from
fishes, such as sardine, herring and salmon.
Liver oil is obtained by various methods. One common method is cook¬
ing good quality minced fish liver at 85°-95°C. This results in disintegration
of liver cells and freeing of oil. The oil floating on the steam condensate can
be skimmed off by centrifugation. About 300 kilolitres of shark liver oil per
annum is produced in the country (Shakuntala Manay and Shadakshara-
swamy, 1987).

REFERENCES

Bartley, J. 1959. Indian Cookery General for Young House Keepers, pp. 63-78. Thacker & Co.
Ltd, Bombay.
Chatterjee, A.K., Panda, B., Kabade, V.S. and Puttarajappa, P. 1971. Studies on curing and
smoking of poultry. Journal of Food Science and Technology 8(1):28.

324
 MEAT, POULTRY AND FISH

Crean, K. 1982. Handling and storage of shrimp by-catch at sea pp. 65-68. Fish By-catch. ..
Bonus from the Sea. Food and Agriculture Organization of United Nations, Rome; and
International Development Research Centre.
Draudt, H.W. 1963. The meat smoking process—A review. Food Technology 17:85-90.
Joshi, B.P. 1994. Meat Hygiene for Developing Countries, pp. 21-23; 61-62. Shree Almora
Book Depot, Almora, Uttar Pradesh.
Karsten Back Olsen and Poul Hansen, 1982. Handling mixed catches, pp. 59-60 (in) Fish By-
catch ... Bonus from the Sea, pp. 59-60. Food and Agriculture Organization of United
Nations, Rome; and International Development Research Centre.
Margaret, Me Williams. 1968. Food Fundamentals, pp. 173-242. John Wiley & Sons, Inc.,
London, New York.
Mudambi, S.R. and Shalini Rao. 1993. Food Science, pp. 131-132.Wiley Eastern Company
Ltd, New Delhi.
Osee, H and Bennion, M. 1970. Introductory Foods, pp. 180-181. The Macmillan Co, and
Collier-Macmillan Ltd, London.
Shakunthala Manay, N. and Shadaksharaswamy, M. 1987. Foods: Facts and Principles, 406 pp.
Wiley Eastern Ltd, New Delhi.
Swaminathan, M. 1987. Food Science, Chemistry and Experimental Foods, pp. 247-251. The
Bangalore Printing and Publishing Co. Ltd, Bangalore, Karnataka.
Varadarajulu, P. 1973. Processing procedures dnd their effects on meat chemistry, short term
course on marketing poultry and poultry products. Indian Veterinary Research Insitute,
Izatnagar, Uttar Pradesh.

LEARNER'S EXERCISE

1. Explain the changes that are brought about in meat on cooking.

2. What are the factors to be considered in selecting fish, and how do you cook them?
3. What points do you remember while selecting the poultry and how do you cook them?
4. Explain the changes that take place in meat when subjected to different kinds of process¬
ing/cooking.
5. Write about canning, curing, freezing and controlled atmosphere storage.
6. What type of spoilage is common in fish? Give reasons.
7. Explain the tenderisation process of meat.
8. Explain the various factors affecting the tenderness of meat. How can you increase the
tenderness of meat?

325
 .

'

.
Part V

Baking process and

products
 , ■
- X *

r.

• ••

>

?.• -
.
 Baking, ingredients,
leavening agents and ovens ■

BAKING

Baking is a process by which the food is cooked in hot air in a close oven.
The action of dry heat is modified by the steam which arises from the food
during cooking. Bread, cakes, pastry, pudding, vegetables and potatoes may
be cooked by this method. Whether baked in primitive or modern ways,
wheat is to be first ground to a flour. In baking, for each purpose flour of a
particular quality is required for bread making a hard wheat flour contain¬
ing a high level of protein is required. For biscuits wheat flour with a low
protein content is desirable. According to modern specifications, the flour
should also contain minimum levels of nutrients such as vitamins and min¬
erals or other ingredients.

INGREDIENTS

Depending on the nature of the baked products, different types of flours are
milled. The types of flours made for baking are the following (Shakunthala
and Shadaksharaswamy, 1987):

Bread flour
Bread flour should form good gluten when mixed with water, and form
bread with a good volume when baked. Thus, bread flours should have a
high protein content. They are milled from blends of hard winter and spring
wheats and then moisture content, protein content, ash content, starch
quality, protein quality and particle size are all controlled.

Self-raising flour
This flour is used domestically for making puddings, cakes, pastries
etc. This is made from milling weak wheats of low protein content. Hard
wheat up to 20% can also be used. The moisture content of the flour should
not exceed 13.5% to prevent premature reaction between the chemicals
present in the flour. Sodium bicarbonate and acid calcium phosphate or
some other acid ingredients are the chemicals used in the ratio of 1.16%
bicarbonate and 1.61% acid calcium phosphate on flour weight. A slight
excess of bicarbonate gives rise to an unpleasant odour and a brownish
yellow colouration.
All-purpose flour (household or family flour) is made from hard wheat

329
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

or a blend of hard and soft wheats and has a moderate protein content. It
does not contain self-raising agents. It is suitable for use in yeast and quick
breads, biscuits, pastries and cakes. A variation of this flour is ‘instantized
flour’ — an instant blending flour. This is made by a special agglomerating
procedure whereby a number of individual flour particles are combined.

Biscuit flour
This flour is made from weak wheats of low protein content. Depending
on the type of biscuit, special types of flours are made. The flour should
make a dough having more extensibility but less spring (resistance) than
bread dough. Dough pieces should retain their size and shape after being
stamped out. The extensibility of biscuit flour dough may be increased by
treatment with a proteolytic enzyme, or with the reducing agent
sulphurdioxide, or by the addition of sodium metabisulphite to the doughs.

Cake flour
Cake flour is a medium-strength flour ground from soft low protein
wheat of low a-amylase activity and is very fine in structure. The purpose of
flour in cakes is to allow an aerated structure to be retained after the cake
has been made. The stability of the final cake depends largely on the pres¬
ence of uniformly swollen starch granules. Hence the starch granules should
be undamaged during milling, free from adherent protein and unattached
by amylolytic enzymes.

Pastry flour
Pastry flours similar to cake flour are made of soft wheat and are fairly
low in protein. They are finely ground and they can be used for all baked
products other than breads.

Water
Water makes possible the formation of gluten.
Gluten: Gluten as such does not exist in flour. Only when flour proteins
are hydrated gluten is formed. Water assists in the control of dough tem¬
peratures (warming and cooling). Water also makes possible enzyme activity.
Home baking is one of the easiest ways of cooking and nothing is more
rewarding than delicious home-made cakes or cookies. The virtues of baked
products are many. They are easy to make and are economical too. They
pose no problem while packing, as they are light and could be easily carried.
They are nutritious and are easily digestible. The retention of nutrients is
better in baked products than that in fried products. Baked foods are suitable
for any occasion and they suit the palate of the old and young alike. Incor¬
poration of baked products in our daily diet is a must not only for nutritional
improvement but also for enhancing the palatability and relieving the mo¬
notony of any food or diet (Kandhari, 1988; Longman, 1986).
Bakery industry in India is one of the most important processed food

330
 BAKING, INGREDIENTS, LEAVENING AGENTS AND OVENS

industries and also the fastest growing one. Every year nearly 0.35 million
tonnes of cookies are produced and sold in Indian market. Baked products
are popularly consumed as snacks by people of all classes and of all age
groups. As such these products may be considered as ideal carriers for the
supply of nutrients to the vulnerable groups like growing children, pregnant
mothers and convolescents. Baked products even play a vital role in popu¬
larizing wheat in traditionally non-wheat-consuming regions of the world.

LEAVENING AGENTS

A leavening agent aerates the mixture and thereby lightens it. Leavening
action may be produced by physical, chemical or biological means. The com¬
mon leavening agents are air, steam and carbon dioxide (C02) (Swaminathan,
1990).

Air
Air is incorporated into flour mixtures by: beating eggs; folding and
rolling doughs; creaming fat and sugar together; sifting the dry ingredients;
and beating batters

Steam
Steam is probably produced in all flour mixtures to a certain degree,
since all flour mixtures contain water and are usually heated to the
vapourization temperature of water. Although the steam produced during
baking causes the mixture to expand, steam alone cannot leaven a mixture.
Its action must be combined with that of air and/or C02.

Carbon dioxide
The principle means of leavening flour mixtures is by the formation of
carbon dioxide generated by the action of chemical leaveners or produced
from sugar by the action of yeast, microorganisms; chemical leaveners include
baking powder, baking soda and ammonium carbonate.

Baking powder
It is defined as the leavening agent produced by mixing of an acid react¬
ing material and sodium bicarbonate, with or without the addition of starch
or flour. Baking powders are classified, according to their action rates. Fast
acting ones give off most of their gas volume during the first few minutes of
contact with liquid. When such powders are added to a mixture, the mix¬
ture must be handled quickly to avoid loss of carbon dioxide and volume.
Slow acting powders gives up very little of their gas volume at low tempera¬
tures, they require the heat of the oven to react completely. Double acting
baking powders begin to act at low temperatures and give viscosity and
smoothness to the batter, but they do not go into complete reaction until
they are exposed to high temperatures.

331
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Baking soda
The reaction of baking soda is similar to the baking powder as a leaven¬
ing agent. Carbon dioxide is released when the baking soda comes into
contact with the liquid in the dough. The amount of baking soda must be
only one-fourth of the amount used for baking powder in any recipe.

Yeast
Yeast helps in fermenting the dough, carbon dioxide is produced as a
result and thus it helps in leavening. Yeast, a microscopic unicellular plant
reproduces rapidly under suitable conditions of food, warmth and moisture.
Yeast in 2 forms, i.e. compressed and dry forms are available. Dry yeast is
used preferable in most of bread varieties (Westland, 1984).

Bread improver
The finest bread improver is a good craftsman. Flour is always of vari¬
able quality, depending on the grade. Bread improver may be divided into
three main classes.
(i) Those of a mineral nature, mainly used by main classes.
(ii) Those of an organic nature, mainly enriching agents.
(iii) Those which, while coming under categories 1 and 2 are also valuable
yeast foods, helping the yeast to work more vigorously.
Sodium chloride
The most important mineral addition to bread is common salt (sodium
chloride). Salt lowers caramalization temperature of cake batter and aids in
obtaining crust colour. Salt improves grain and texture of loaf by strength¬
ening the dough.
Persulphates
The persulphates used are potassium and ammonium. Flours treated
with persulphates take more water to allow for the tightening which takes
place as fermentation proceeds; in this way increased yield is obtained
(Wilfred, 1976).
Potassium bromate
Bromate has an estringent action on glutin, necessitiating the use of
more water in the dough. It improves the gas-retaining properties of the
gluten, and then increasing loaf volume.
Phosphates
Acid calcium phosphate and ammonium phosphate both have a tight¬
ening action on gluten, and since phosphates are necessary constituents of
yeast food, they are both fermentation stimulants.
Lime water
As lime is alkaline, it reduces the acidity of the dough and then slows
the speed of fermentation.
Organic acids
Lactic and succinic acids are natural constituents of a fermenting dough,
so that an addition, within limits, can be made with perfect safety.

332
 BAKING, INGREDIENTS, LEAVENING AGENTS AND OVENS

EQUIPMENT

Equipment used to measure dough quality or rheology

Rheology is the science of formation and deformation of dough and of
flow of batter. It mainly includes viscosity, elasticity and plasticity. Dough¬
testing apparatus are of two types: dynamic and static.
Those which automatically record the properties of a dough over a pe¬
riod of up to 20 min. of continuous mixing may be termed dynamic. The
static type record the stress and strain relationships during the short time
taken to stretch a piece of dough until it breaks. The various instruments
used are: recording dough mixers, load extension meters, extrusion meters,
penetrometers and texturometers.
Recording dough mixers
These record the power needed to mix a dough at constant speed. The
curves obtained yield information about changes in rheological (dough) prop¬
erties during mixing. The curves usually consist of a rising part, showing an
increase in resistance with mixing time, followed by a more or less slow
decrease in resistance. The maximum is either flat or broad or peaked de¬
pending on the type of instruments and type of flour. The curves indicate
the rate of dough development and subsequent breakdown. Maximum re¬
sistance indicates optimal development of the dough. The instruments com¬
monly used are Brabender farinograph, Swanson and working mixograph.
Some of them are explained below.
Farinograph
This is a dough-testing equipment of the dynamic type as the resistance
offered by a dough to constant mechanical mixing under consistent test
conditions is measured from the very moment the dough is formed. The
graphical record thus obtained is an energy-time diagram and is a criterion
on the general quality characteristics of the flow.
The instrument consists of a twin-bladed water-jacketed mixer, operated
by an electric motor which is free to rotate about its axis when a torque is
applied by the resistance of a dough to the action of the mixing blades. The
motor housing is connected through a damping device to a pen which oper¬
ates over a moving band of paper. During the mixing of a wheat flour dough
in this instrument, the pen traces a curve on the paper, the shape and
general configuration of the curve depending on the physical properties of
the dough. The paper is printed with a scale along its length indicating the
time in minutes, and across its width, an arbitrary scale of 0-1,000, which
measures the consisency of the dough (Fig.47).
A typical farinograph curve gives an idea of (a) water absorption per¬
centage to produce a dough showing a consistency of 500 Brabender units,
(b) dough developing time in minutes indicates the mixing time required by
the flour, from the moment doughing up starts to the time it reaches optimal

333
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Fig. 47. Farinograph, a dough-testing equipment of dynamic type

dough development and attaining at the same time maximum width of the
band, (c) dough stability, in minutes, represents the time during which there
are no changes in the consistency of the dough after it has reached its
optimum development. The sum of dough development time and dough sta¬
bility time is considered as the resistance of the dough, (d) width of the
curve represents elasticity, (e) weakening of the dough is measured in
farinograph units and is represented by the difference in dough compact¬
ness after a further mixing.
Mixograph
This equipment is mostly used in America and is a dynamic type. It
consists of vertical cylinder (bowl), open at the top. This contains four fixed
vertial pins fastened to the bottom. A head piece, which could be lowered
into the cylinder also contains four pins and is rotated through flour and
water kept in the bowl, dough development occurs in the cylinder which, if
let free, would have rotated. This movement is restricted by a spring, so that
the twist could be measured and recorded.
As the dough develops, the curve rises to a minimum. The curve then
descends and as the doughing continues, a curve more or less similar to
that given by a farinograph is obtained. The steepness with which the curve

334
 BAKING, INGREDIENTS, LEAVENING AGENTS AND OVENS

rises, its height and the manner in which the curve descends after the
maximum are associated with above flour characteristics.
Load extension meters
These instruments measure the load required for the rupture of the
dough when it is stretched. The curve of load versus stretching of dough is
recorded. From these records, resistance against deformation and extensi¬
bility can be read. The instruments commonly used are Brabender
extensograph, Chopin Extinsograph, Halton extensograph etc.
Alveographe (chopin extensimeter)
This is a static type of dough-testing instrument which records the stress/
strain relationships in a dough while the dough is stretched until it breaks,
but it employs a different method for deforming the dough. A disc of dough
is blown into a bubble by means of air pressure, and the pressure within
the bubble is recorded continuously from the time the bubble starts to form
until it finally ruptures. All dough tested contain the same proportion of
total water. Based on the area of alveographe the flour/dough can be di¬
vided into three main types, viz. weak, medium and strong. Alveographe is
helpful in determining the dough stability by the height of the peak; and
dough extensibility by the base line and measure of the strength of the
dough by the area enclosed by the curve.
A typical alveographe curve is shown in Fig.48 and the alveographe
instrument is given in Fig.49.
Extrusion meters
These instruments measure the amount of force required to extrude
the dough. They are not commonly used for measuring dough quality.
Penetrometers
In recent years, penetrometers are being used extensively in some Eu¬
ropean countries for measuring dough strength. They are not commonly
used in America.
Maturographs
These instruments are used to measure the properties of fermenting
dough. The instruments commonly used are Brabender maturograph, Cho¬
pin zymatochygraph etc.
Zymotachygraphe
This is an instrument designed to record automatically and simultane¬
ously both gas production and gas retention. The zymotochygraphe instru¬
ment is shown in Fig.50.
A fermenting dough is placed in the thermostatically controlled fermen¬
tation chamber, and once every 2V* min. This chamber is automatically put
into connection with the water manometer, which carries a pen operating
on a moving sheet of paper. The first four connections are made direct, so
that the pressure recorded is that of the total as produced by the yeast,
whether it is retained within the dough or has escaped from the surface into
the fermentation chamber. The next four 2 Vi min readings are automatically

335
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Fig. 49. Alveographe, a static type of dough-testing instrument

Fig. 50 Zymotachygraphe, an instrument used to record automatically and simultaneously both production
and retention of gas

336
 BAKING, INGREDIENTS, LEAVENING AGENTS AND OVENS

macte by way of an absorption vessel, which removes any C02 which has
escaped from the dough, and they measure, therefore, only the gas retained
within the dough. When the stage is reached at which dough allows the gas
to escape, the consecutive blocks of four readings vary in height, the higher
blocks indicating total gas produced and the lower blocks gas retained.
Barbender amylograph
The gelatinization of starch within the loaf during baking has an influ¬
ence on the condition of the crumb of the baked loaf, i.e. whether it is dry,
sticky or normal.
The amylograph simulates the effect of baking on starch step by step,
by raising the temperature of a flour/water suspension at a constant rate,
during which the starch gelatizes. A graph is recorded, the height of which
is related to the viscosity of the paste. A high curve reveals a starch with a
good water-binding capacity resulting in bread with a dry eating crumb. A
low graph line shows a starch with a low water-binding capacity and is
usually indicative of high alpha-amylase activity which will result in a damp
sticky crumb. The mean between the two, shows the most suitable flour for
breadmaking.
Extensometer
This instrument gives a curve which is similar in shape to that pro¬
duced by the extensograph (Hill, 1960).
For the extensometer test the dough is shaped into a ball and placed
upon 2 spikes, and when the instrument is set in operation the lower of
these spikes moves downward while the top one remains stationary. The
tension in the loop of dough that is formed, and the extent to which the
dough is stretched is recorded on a moving sheet of paper until the dough
breaks. As the flour is progressively treated the dough yields become pro¬
gressively less extensible but more stable. This finding has led to the sug-

Fig. 51. Extensometer

337
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

gestion that the area under an extensometer curve is a measure of the

potential strength of a flour. Diagramatic representation of extensometer is
given in Fig.51.
Extensograph
The test consists of stretching a dough of culindrical form by means of
a moving arm. The stress produced in the dough by its resistance to exten¬
sion is recorded in a graphical form. It is suited for testing fermented dough
and for studying the effect of improvement on dough.
Five types of doughs can be distinguished with the help of this equip¬
ment. These are plastic short dough, short and stiff dough, elastic and ex¬
tensible dough, extensible dough and flowy dough.
Food texturometer
The general foods texturometer is a well-known instrument in this cat¬
egory. The principle of this instrument is shown in Fig. 52.

Fig.52: Principle of the general foods texturometer

Samples of the five biscuit types, conditioned at seven different relative

humidities, were subjected to the following series of instrumental tests (a) a
simple beam, centre load end support, bend test; (b) a cantilever beam, end
load bend test; (c) a direct shear test; (d) a uniaxial compression test; (e) a
‘bulk’ compression test; (/) a uniaxial tension test; (g) a charpy impact test;
and (h) an FMBRA biscuit texture meter test. The principles of tests (a) to (g)
are illustrated in Fig.53 (Birch etal, 1997).

TERMS COMMONLY USED IN BAKING

The terms of commonly used in Baking process as per U.S. Wheat Asso¬
ciates (1988).
338
 BAKING, INGREDIENTS, LEAVENING AGENTS AND OVENS

Fig.53. Principles of tests applied to biscuits in the study of crispness and brittleness, (a) centre load, end
support, bend test; (b) end load, end support, bend test; (c) shear test; (d) uniaxial compression
test; (e) bulk compression test; (f) uniaxial tension test; (g) charpy impact test

Aeration: The treatment of dough or batter by charging with gas to pro¬

duce a volume increase.
Adhesiveness: Work necessary to overcome the attractive forces between
the surface of product and adhesive material.
Bake: To cook a roast by dry heat in a closed place such as an oven.
Baking powder: A chemical leavening agent composed of soda, dry acids
and corn-starch (to absorb moisture), when wet and tested carbon dioxide
is given off to raise the batter during baking.
Batter: A homogenous mixture of ingredients with liquid to make a mass
that is of a soft plastic character.
Bread: The accepted term for baked foods made of flour, sugar, shorten¬
ing, salt and liquid, and leavened by the action of yeast.
Brittleness or crispyness: The force required to break the material
Caramelized sugar: Dry sugar heated with constant stirring until melted
and dark in colour, used for flavouring and colour.
Carbon dioxide: A colourless, tasteless edible gas obtained during fer¬
mentation or form a combination of soda and acid.
Clear flour: Lower grade and higher ash content flour remaining after the
petent flour has been separated.
Colours: Shades produced by the use of dyes.
Creaming: The process of mixing and creating shortening and another
solid such as sugar and flour.

339
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Chewyness: The force required to degenerate semi-solid to slaky or pasty

or ready to swallow consistency.
Cohesiveness: It is the strength of the internal bonds making the body of
product.
Dough: The thickened mass of combined ingredients for bread, rolls and
biscuits, but usually applied to bread.
Dusting: Distributing a film of flour or starch on pans or work bench
surfaces.
Elasticity: Slight deformation caused by force, retained after force removal.
Fermentation: The chemical changes of an organic compound due to action
of living organisms (yeast or bacteria) usually producing a leavening action.
Gliadin: One of the two proteins comparising gluten which provides
elasticity.
Gluten: The elastic protein mass that is formed when the protein mate¬
rial of the wheat flour is mixed with water.
Glutenin: One of the two proteins comprising gluten, which gives strength.
Greasing: Spreading a film of fat on a surface.
Hardness: Force necessary to attain a given deformation.
Hearth: The heated baking surface of the flour of an oven.
Leaveng: Raising or lighting by air, stear or gas (carbondioxide). The agent
for generating gas in a dough or batter is usually yeast or baking powder.
Mix: The combined ingredients of a dough or batter.
Moulder: Machine that shapes dough pieces for various shapes.
Parker house rolls: Folded buns of fairly rich dough.
Plasticity: Material does not regain its original form even after
force removal.
Proof box: A tightly closed box or cabinet equipped with shelves to permit
the introduction of heat and steam used for fermenting dough.
Proofing period: The time during which dough rises between moulding
and baking.
Steam: Vapour formed and given off from heated water.
Temperature: Degrees of heat or cold.
Tempering: Adjusting temperature of ingredients to a certain degree.
Troughs: Large containers usually on which used for holding large masses
of raising dough.
Vienna colour: A hearth-type bread with heavy crisp crust, sometimes
finished with seed tapping.
Viscosity: Rate of flow per unit force in a given time.
Yeast: A microscopic plant which reproduces by budding and causes
fermentation and the giving off carbon dioxide.

TYPES OF BAKING OVENS

Various kinds of fuels can be used for heating ovens. The ovens may differ

340
 BAKING, INGREDIENTS, LEAVENING AGENTS AND OVENS

considerably in structure and they can be easily classified as coal, coke or

oil-fired or heated by gas or electricity (Albert, 1963).

Internally-and externally-fired ovens

The baking chamber of an oven can be heated by the application of heat
externally or internally. Internally-heated ovens of several classes still exist
and all of them are to be found doing active service in various parts of the
country (Wilfred, 1976). They are:
1. The side-flue or early prototypes of this oven
2. Small domestic gas cookers and cabinet ovens
3. Modern travelling biscuit ovens heated by gas
4. Some types of reel ovens
Other types of ovens are heated externally. This means that the fuel is
burn outside the baking chamber and the heat carried by various means to
inside of the oven. Goods can be baked in externally-heated ovens are being
fired, and although this equally applies to internally-heated gas and electric
ovens it cannot apply to those internally-heated fired with coal, coke or fuel-
oil. The reason is that the latter produce smoke, soot, fumes, etc., which
would soil the goods in the oven, whilst the flames that issue from these
fuels would ignite the bread, etc. and consume it.

Side-flue and similar ovens

This class of oven may still be seen in use, particularly in India, and many
people believe that bread baked in them is much better to eat than that baked
in more modern types of steampipe oven. Field ovens of the kind previously
used by the army, faggot ovens and Scotch chaffer ovens, as well as ordinary
side-flue ovens consist of a baking chamber fitted with a door. An oven stock
is present in all of them except field ovens. The method of heating varies. The
field oven is filled with wooden logs which burn directly and heat the mate¬
rials of which the oven is constructed as well as the clay spread thickly over
the top of it and the tiled or earthen floor or sole (Fig. 54).

Steam escape trap

Oven doop
Oven stock

Fig. 54. The slide-flue oven, side elevation

341
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

When the wood has burned long enough to heat these surfaces suffi¬
ciently, the goods are placed into chamber to bake. The aperture acting as
the door is closed with a metal sheet and the chinks plugged up with clay. It
is very close to the faggot ovens in use in the continent in small French and
Belgian village bakeries. Here the oven is usually a permanent structure,
stoutly built of brick with tiled sole and arched crown. On the top of the
crown a thick layer of sand is provided to act as a heat reservoir and insultator.
Faggots of wood are lighted inside the oven which is also fitted with a damper
and a chimney to carry off the smoke. The wood flames away whilst the
dough is being scaled, handed-up and moulded and are raked out into a bin
standing beneath the oven stock aftc proof is completed. The bin is then
pushed under the oven out of the way whilst the baker swabs the sole of the
very hot oven with a scuffle pole. This is a long pole to which a sack is
fastened with a short length of chain. The sack is dipped into a bucket of
water, then inserted into the oven and the sole well swabbed over to get rid
of soot and ashes. The door is then closed for about 10 min. to allow the fine
or flash heat to be absorbed by the brickwork. After this the bread is set and
allowed to bake. There is no method of testing the exact temperature. The
baker judges this from his experience.
The Scotch chaffer oven is similar, except that the fire is contained in a
metal, basket-like affair called a chaffer. Coal is the fuel rather than wood.
Another variation is the wagon oven and in this the fire is lighted in a con¬
tainer called a wagon which is then inserted in the oven. Finally the best
form of all these ovens is the side-flue. As its name implies the fire is lighted
in a furnace at one side of the oven. Coal or wood is generally used but in
more recent years fuel-oil and even gas burners have been adapted to side-
flue ovens. A large fire is required and good gaseous coal is needed, so that
a long tongue of flame extends across and round the oven to the other side
of the door where the chimney, with damper, is fitted. No method of ascer¬
taining the temperature is available on most side-flue ovens, although
pyrometers are fitted to some. The experienced baker knows when the oven
is hot enough by observing that the soot-blackened back wall of the oven
turns to a whitish ash colour. The baken then get rid of any flaming or
smoking coals in the furnace very quickly or a lot of heat roar away up the
chimney. Having a clear fire, a small bowl of water is thrown over the hot
ashes which have fallen through the fire bars into the ashpit. This creates a
little steam which rises, passes through the fire, becomes superheated and
improves the atmosphere of the oven. The damper is closed and a period of
20 min. allowed, so that the walls, sole, and crown absorb the flash heat.
The oven can then be scuffled out to clean the sole of soot and ashes before
the bread is set.
Advantages of side-flue ovens
Advantages of side-flue ovens are:
1. Produce bread of excellent flavour, with appetizing crusts, when
skilfully operated. _
342
 BAKING, INGREDIENTS, LEAVENING AGENTS AND OVENS

2. Very cheap to maintain. Once they are properly constructed the

only new fire bars occasionally and furnace-brick renewals. Rarely
the oven requires resoling with new oven tiles.
3. Owing to the great thickness of the walls, etc. there is a great re¬
serve of heat which can be utilized for baking many small goods
throughout the day after bread-baking completed.
Disadvantages of side-flue ovens
Disadvantages of side-flue ovenm are:
1. They are very dirty to operate.
2. Coal has to be brought into the bakehouse and ashes to be wheeled
out almost daily.
3. In no sense are they continuous. When one batch of bread is drawn
the oven must be refired, damped down and scuffled out before a
second batch of bread can be baked.
4. When solid fuel is used they create a very unpleasant sulphury
odour (sulphur dioxide) in the bakery.
5. Owing to their construction they tend to harbour hosts of blackbats,
cockroaches, silver fish and crickets.

Steam-pipe ovens or steam-tube oven

The introduction of steam-pipe ovens marked a great advance on the
side-flue. They rely for their heating upon a series of very strong tubes, each
of which contains a small quantity of water hermetically sealed within the
narrow bore running along them. By sloping the tubes slightly towards the
furnace the water runs down to the end. As the tubes can be sloped towards
the back, or be set transversely and therefore sloped to either side, the
furnace can be arranged in any position to suit the convenience of the
premises. It is not at all necessary to have the furnace inside the bakery and
it is generally situated at the back of the oven in a small apartment separate
from but adjoining the bakehouse.
Small pea-sized coal can be used in automatic stokers attached to these
ovens, but coke, gas, or fuel-oil is quite frequently used for firing steam-pipe
ovens. When the fire is lighted the water in the tubes boils and steam is
produced. This cannot escape as the tubes are hermetically sealed. As heat
continues to be applied more and more steam is formed, so that pressure is
brought to bear on the surface of the remaining water.
As pressure increases on the surface of a liquid, its boiling point in¬
creases. Steam creates pressure which raises the boiling point of the water
from 100°-100.6°C. Apply heat continuously to raise the boiling point of
water as high as 260°C. This heat is equal throughout the length of the
tube, though heat is applied only at one end, and the whole oven is heated.
Rows of these tubes are placed under the oven crown and just under the
sole to heat the top and the bottom of the oven (Fig. 55).
The tubes are evenly spaced apart. In some of the earlier ovens of this

343
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

type the tube-ends extend into a furnace running right across the back or
along the whole length of the side of the oven. In such cases, it is important
that fire is spread evenly along the whole length of furnace or tubes which
are not near enough to the fire will not be properly heated and the oven will
be unevenly heated. In better-planned more modern ovens the tubes are
bent around to form a compact bank in a small furnace. This arrangement
is excellent for all practical purposes, evenly heats the oven and uses less
fuel.
As the furnace in this type of oven is in a compartment built outside the
baking chamber with which it has no connection except for the tubes which
pass through the dividing wall, no fumes reach the baking chamber and
baking can proceed at the same time as firing of the oven is being carried
out. Thus one batch of bread can follow closely on another. No ashes or soot
get into the oven so that it is not necessary to use a scuffle pole and swab
after the baking of each batch, but this should be done occasionally to re¬
move any debris accumulating in the oven.
Advantages of steam-pipe ovens
Following are the advantages:
1. Continuous baking is possible.
2. They are clean to work.
3. Thermometers and pyrometers can be used with safety and are gen¬
erally fairly reliable.
4. No fumes collect in the bakery hence working conditions are more
comfortable and congenial.

344
 BAKING, INGREDIENTS, LEAVENING AGENTS AND OVENS

5. No fuel enters and no ashes have to be wheeled out through the

bakehouse.
6. Economical in the use of fuel.
Disadvantages of steam-pipe ovens
1. Expensive to install.
2. Dangerous when under the control of careless operatives who, by
failure to keep an eye on the thermometer, may overheat them. This causes
excessive pressure to be set up within the tubes which may possibly burst.
The explosion that follows can do great damage and may result in a completely
wrecked oven. In careful hands this rarely happens.
3. Repairs necessitated by burst tubes are expensive.
4. Regular examination by a qualified engineer is necessary and legally
enforced at stated intervals of time, to warn the proprietor of pending trou¬
bles caused from the burning out of tubes. Such worn tubes must be replaced
if the oven is to maintain a high standard of efficiency.
5. Much time is needed to raise or lower the temperature to any great
extent.

Hot air ovens

There are various patterns of patented ovens, heated by hot-air currents
passing through ducts concealed in their soles, crowns and side walls. These
ovens are continuous, for the furnace and all hot air ducts are outside the
actual baking chamber (Fig. 56). There is no possibility of explosion, otherwise

345
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

the advantages and disadvantages are similar to those of the steam-pipe

oven.

Peel and drawplate ovens

Whichever form of continuous-baking oven is chosen it can be had in a
variety of designs. There is ordinary peel oven which has no moving parts
and is simply an improvement on the side-flue oven. This type of oven can
be had as a one-, two-, three-, four-, and five-decker. So also can be side-
flue although a double-decker side-flue is generally the limit in this direc¬
tion. Each deck may be arranged for independent heating, so that it is possible
to bake goods which require vastly different temperatures at the same time,
e.g. a batch of bread at 237.8°C in one oven and a batch of slab cakes at
182.2°C in the other.
The next variation is the drawplate. In this type the sole of the oven
consists of a stout metal plate running on suitable apparatus and capable of
being pulled out to its fullest extent into the bakery where it can be loaded
as desired and then be pushed back gently into place again. Such an ar¬
rangement inevitably loses much heat both on account of the door having to
be the whole width of the oven and the loss, by radiation, from the heated
plate on withdrawal. Despite this, drawplate ovens are very good and bake
bread perfectly.

Vienna ovens
The Vienna oven is different from all others in that its sole slopes at a
considerable angle upwards from the door to the back, though not as steeply
as indicated by the accompanying diagram. When the door is opened little
or no steam can escape, the latter rising so being trapped in the higher
portion of the baking chamber. It is therefore possible to open the oven door
and to insert bread and rolls continually without losing much steam during
the process.

Fig. 57. The Vienna oven steam tube

1346
 BAKING, INGREDIENTS, LEAVENING AGENTS AND OVENS

At the top of the slope there is a steam-escape damper. This can be

opened at the appropriate time to enable the steam to be drawn off. Fig. 57
gives the principles of Vienna oven.
Apart from these items of construction there is a little difference be¬
tween Vienna and ordinary bread ovens. They can be fired by any of the
fuels and can be of the steam-pipe or hot-air pattern. If the oven is a steam-
pipe model then the furnace is usually at the front.

Adapting an ordinary oven for baking Vienna bread

Some form of steam trap must be devised to keep the steam back when
the oven door is opened to admit the loaves or rolls. The best method is to
have a metal plate cut to fit the contour of the oven mouth but leaving a gap
3.81-7.62 cm wide between the bottom edge of the steam trap and the
bottom of the oven. Through this narrow space the rolls or loaves can be
inserted without scraping the tops of them. In order to keep the steam trap
in position two bolts must be fixed into the arch of the oven mouth but
should not be screwed right home. This leaves about 0.317 cm of the body
of each bolt available for forked metal clips to slide between the heads of the
bolts and the metal framework of the oven mouth. The clips are riveted at
right angles to the metal steam trap, so that the latter can be clipped into
position when the oven is required for the baking of Vienna bread. The other
point to bear in mind is that the bolts must be placed so that when the
steam trap is in use the oven door can be properly closed.

Travelling ovens
The various travelling ovens, including the rotary and reel types, in
which either the sole of the oven, or swinging shelves on which the goods
can be placed, travel continuously through the baking chamber. All kinds of
arrangements are possible. In some the ovens are of great length and the
endless steel sole (usually called the hand’) travels at the required speed
through the lengthy baking chamber, discharging correctly-baked goods at
the opposite end to that at which they entered. This type is now most com¬
monly used for large-scale biscuit baking and for swiss roll production. In
others the goods travel on baking sheets carried along by a pair of endless
chains or metal belts. The trays are placed in position, carried through the
oven by the mechanism and taken off as they emerge at the other end. In
this type of oven, which is largely used in confectionery manufacturing, two
or three separate rows of baking sheets may be passing abreast along the
oven at the same time. Still another variation, to be seen in use as part of an
automatic bread-making plant, consists of an arrangement of swinging trays
or shelves which pass a single aperture. At this position they are both loaded
and unloaded.
All types of travelling ovens can be heated by coke, electricity, gas, fuel-
oil or fine coal fed to the oven mechanically by an automatic stoker. Choice

347
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

of fuel, and therefore of design, needs much consideration before a new

oven is installed.

REFERENCES

Albert, R. D. 1963. Bakery Materials and Methods, edn 4, pp. 185-99. Maclaren & Sons Ltd,
London.
Birch, G.G., Brenner, G.G. and Parker, K.J. 1997 Sensory Properties of Foods. A S Applied
Science Publishers Ltd, Delhi.
Hill, D.G. 1960. Quality Testing of Baking Products — Bakery Technology and Engineering, AVI
Publishing Co. West Port, Connecticut.
Kandhari, L.R. 1988. Bakers Handbook on Practical Baking. 902 pp. New Delhi House, New
Delhi.
Longman, O. 1986. Basic Food Preparation. A Complete Manual Orient. Longman Ltd, New
Delhi.
Shakunthala, M.N. and Shadaksharaswamy, M. 1987. Foods: Facts and Principles, 257 pp.
Wiley Eastern Limited, Bombay.
^Swaminathan, M. 1990. Food Science, Chemistry and Experimental Foods. The Bangalore Print¬
ing and Publishing Co. Ltd, Bangalore.
Westland, P. 1984. A Practical Guide to Health Foods Recognising, Preparing and Cooking Natu¬
ral Foods. Columbia Books, London.
Wilfred J. F. 1976. The Students Technology of Bread Making and Flour Confectionery. Rovtledge
and Kegan Paul, London. Henley and Boston.

LEARNER’S EXERCISE

1. What are chemical leavening agents? Describe their role in Indian food preparation.
2. Write in detail about the leavening agents and their functions in baked products.
3. Explain acid present in fast acting baking powder with suitable examples.
4. Write in brief about the following:
(a) Self raising flour; (b) Cake flour; (c) Bread improver.
5. Write about the various equipment used to measure the dough quality or rheology.
6. Name some of the baking ovens used in bakery industry.

348
 Biscuits, breads
and rolls

BISCUITS

T he biscuit industry has made rapid progress in recent years in India and
several other developing countries. Successful attempts have been made
to enrich biscuits with proteins, vitamins and minerals (Barrows, 1975).
Various formulations are given in Table 36.
Table 36. Formulae for various biscuits

Ingredient Salt Sweet Fruit Coconut

(g) (g) (g) (g)

Flour 260 170 115 200

Fat 100 85 100 100
Sugar 50 85 30 100
Egg 50 - 20 50
Ammonium bicarbonate 4 - - -

Baking powder 3 2 3 3
Milk - 70-100 ml - -

Essence - Few drops Few drops Few drops

Water 25 ml - - -

Coconut (desiccated) - - - 50
Tuity-fruity - - 30 -

Cashew nuts - - 25 -

Method
• Sift flour with baking powder thrice.
• Cream butter and sugar till light and fluffy adding essence.
• Add flour to make pliable dough.
• Roll out into 0.31 cm thickness and cut with a biscuit cutter.
• Separate the biscuits.
• Bake at 195°C for 15 min.
Important points to remember in making different types of biscuits.
Salt biscuits: Add baking powder, salt and ammonium bicarbonate to the
creamed mixture. Coat with egg before baking.
Fruit biscuits: Add cleaned and chopped fruits in the flour.
Coconut biscuits: Add desiccated coconut to the flour and some at the
time of rolling.
Masala biscuits: Add 10 g masala powder in the flour, sieve twice.

349
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Tri-colour biscuits: Sandwitch a plain biscuit with one hole using a thin
layer of jam. Sprinkle with icing sugar and fill each hole with different col¬
oured jam in each hole.

BREAD

Bread industry in India is growing rapidly to meet the increasing demand of

bread which has gained popularity in the Indian diet because of its avail¬
ability at reasonably cheaper rate. A good bread can be prepared from four
basic essential ingredients, i.e. wheat flour (maida), yeast, salt and water.
Maida quality plays an important role in the production of bread. Many
additives are used during mixing the dough which within limit corrects dough
strength by conferring stability to the gluten to form a fine network and
structure of bread. Certain additives are added to improve the nutritional
quality of bread (Arnold, 1975). There are common procedures for bread¬
making and it includes certain steps (Fig. 58). Sponge bread-making includes
different steps (Fig. 59).

350
 BISCUITS, BREADS AND ROLLS

50% flour + yeast water

The batter is kept aside sponge stage for 3-4 hr / -► Sponge stage
i
Sponge like appearance
/
I \
Add remaining 50% flour,
salt, sugar and fat
I
Dough formation
1 ^ Dough stage
Kneeding and fermenting dough stage
for short period
i
Proofing and baking

Fig.59. Process of sponge bread-making

The common method of preparation of bread using various ingredients

is given below (Kent, 1984; Longman, 1986).

Bread
Ingredient Normal straight dough No time dough Tin bread

Maida 300 g 300 g 200 g

Fat 8g 10 g 6.6 g
Salt 5g 5g 3.3 g
Sugar 10 g 15 g 10 g
Fresh yeast eg 6 g dry 8g
Water 180 ml 180 ml 180 ml

Method
• Mix yeast in lukewarm water and keep aside. Add a teaspoon of
sugar.
• Dissolve salt and sugar in remaining water and strain.
• Sieve the flour. Mix water in which salt and sugar have been dis¬
solved with the flour roughly.
• Add yeast mixture to the flour and knead to a smooth and soft
dough add more water, if necessary.
• Cream the fat and knead it to form the dough.
• Keep the dough in the dry prover at 27.7°C for 1 hr 30 min. to 2 hr.
• Punch the dough and again keep in dry proof for 55 min. at 27.7°C
(approx.).
• Divide and scale the dough into balls.
• Keep these balls under a dry cloth at room temperature for about
15-20 min.

351
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

• Roll the mold either by machine or by hand.

• Pour in greased bread tin.
• Keep tin in wet prover at 35°C or under a wet cloth for about 1 hr or
till it fills the tin.
• Spray water on the bread surface before putting into the oven.
• Inject steam into the oven or put a pan with hot water inside.
• Bake bread at 204.4°C for 30-35 min.
• Remove and brush over with oil.
If dry prover is not available, allow dough to ferment till it becomes
double the volume (Salunkhe etal, 1986).

Types of bread
Whole meal bread (brown bread); wheat germ bread; gluten bread -
high protein bread; high fibre bread; Granary bread; banana bread; bread
rolls; short bread; white bread; dinner rolls.
Baking process involves heat transfer (Fig. 60) and it is by conduction,
convection and radiation (Dean et al, 1963). Various sources of energy are
direct fire, indirect fire and steam.

43.3°C (110°F) oven spring

I
62.8°C (145°F) yeast activity ceases

f Sugar caramelizes; protein denaturation

71.1°C (160°F) starch getalinization

76.7°C (170°F) crumb structure set

>1
82.2°C (180°F) moisture loss (8-10%)

Fig.60. Changes in dough at different temperatures during baking of bread

Common defects in bread

The defects could be in external appearance or internal load.
External defects: The external defects are: general insufficient or exces¬
sive loaf volume, light or dark crust colour; blisters on excessive crust thick¬
ness and absence of break and shred.
Internal defects: The internal defects are: gray crumb colour, streaky
crumb, cores (dense spots in the crumb), holes in crumb, poor flavour and
rapid staling and poor keeping quality.

352
 BISCUITS, BREADS AND ROLLS

BREAD ROLLS

Formulation for rolls differ widely, however, regular bread dough may
be used to make rolls of good quality. Basic formulae for rolls are as follows:
Bread-rolls formulae

Ingredient Standard Quick raised Hard rolls Soft rolls Puff rolls
hot rolls yeast rolls (based on (adapted from
French bread standard hot
formula) roll recipe)

Flour, hard wheat (g) 100.00 100.00 100.00 85.00 100.00

Flour, soft wheat 15.00
Water (ml) (variable) 40.00 26.09 56.67 62.00 76.19
Yeast (g) 1.24 2.85 1.85 3.00 4.76
Salt (g) 1.69 2.17 1.67 1.75 0.60
Sugar, total (g) 9.44 9.78 2.92 8.00 9.52
Shortening (g) 10.00 13.04 2.08 12.00 19.07
Milk (ml) 132.22* 65.22 5.00 9.52**

'Evaporated; "non-fat dry.

The steps in roll production are the same as for bread production. Dif¬
ferent kinds of bread rolls available are sandwich rolls, pan rolls, winner (or
finger) rolls, parker house rolls, clover leaf rolls, twin rolls, butterhorn rolls,
poppy seed or sesame seed rolls. The steps in roll preparation are the same
as for bread preparation like weighing and measuring of ingredients, mix¬
ing, fermentation, dividing, scaling, rounding, intermediate proof, makeup,
panning, pan proof baking and cooling.

Makeup of bread rolls

Steps in making bread rolls are:
Sandwich rolls: Makeup is as follows (Fig.61): Divide dough into 1.5 kg
pieces. Round up and let rest 15 min. From each piece of dough into a rope
2.54 cm in diameter. Cut strips of dough into pieces weighing approximately
50 g each (step 1). Round the 50- g pieces into balls by rolling them with a
circular motion on the workbench (step 2). Place rolls in rows on a greased
baking sheet 3.80-5 cm apart. Proof for 15 min. Flatten rolls with fingers to
the desired thickness and finish proofing (step 3).

Problems associated with bread-roll preparation

Temperature: Temperature control is of paramount importance. Dough
temperature should remain at 26.7°C. Too high temperature will cause dough
to ferment too rapidly and rolls become sour or yeasty tasting. However, too
low temperature causes heavy tough rolls.
Fermentation: The amount of time needed depends on the amount of
yeast and sugar used. In quick-raised rolls, for example about twice more

353
TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

354
 BISCUITS, BREADS AND ROLLS

yeast is used and only one formulation period is required because there is
no makeup. Proof time is only of 30 min. duration.
Scaling and shaping: Makeup of bread rolls constitutes the major step in
production. The variety of shapes possible with soft and hard rolls is most
endless. Accurate scaling of dough and skilled manipulation of it in forming
shapes is required by the baker.
Proofing: Since rolls are considerably smaller in size than loaf bread,
proofing time is very critical in terms of volume, time required and
overproofing. Other than these points discussed, problems in bread roll
production do not differ from those in bread production.

REFERENCES

Arnold, Spices. 1975. Bread—Social, Nutritional Agricultural Aspects of Wheat Bread. Applied
Science Publishers Ltd, London.
Barrows, A.B. 1975. Everyday Production of Baked Foods, edn 2. Applied Science Publishers
Ltd, London.
Dean, K.J., Edwards, N.E. and Russell, C.A. 1963. An Introduction to the Physics and Chemistry
of Baking. Maclaren Sons Ltd, London.
Kent, N.L. 1984. Technology of Cereals, edn 3, pp. 191-217. Perganon Press. Pergamon.
Longman, O., 1986. Basic Food Preparation, A Complete Manual, pp. 265-76. Orient Longman
Ltd, New Delhi.
Salunkhe, D.K., Kadam S.S. and Austin, A. 1986. Quality of wheat and wheat products.
Metropolitan Book Co. Pvt. Ltd, New Delhi.

LEARNER’S EXERCISE

1. Explain the various tests and the principles involved in assessing the flour quality.
2. Write the formulae for various biscuits.
3. Explain the common defects in bread.
4. What are the various problems associated with bread-roll preparations?

355
 Cakes, cookies
and pastries

;
CAKE

T he basic ingredients of a cake are divided into two types—the ones that
give structure to the cake—flour, eggs and milk; and the ones that make
the cake tender—sugar, shortening and baking powder.
Ingredients of cake are:

Flour
Flour provides structure for the cake as well as holds the other ingredi¬
ents together. Flour with a protein content of 9%, a fine grain and well
bleached is most suitable for use as a cake flour. Bleaching helps the flour
carry more sugar, water and shortening. The pH of the flour should be
around 5.2.

Sugar
Sugars are used as sweetners. Sugar used for all types of cakes should
be of Fine granulation to ensure an even grain and soft texture in cakes. This
type of sugar dissolves very readily and produces a smooth creamy mass.
Large sugar crystals produce a coarse texture. When creaming the sugar
and shortening, best results are obtained by using dissolved sugar in milk
or water. Eggs and sugar are best beaten when equal amounts of each are
used. Sugar has a mellowing or tenderizing effect on the cell structure and
when too high a percentage is used the cakes are quite apt to sag in the
centre or fall. Shortening also has this effect. Sugars like invert sugar, honey,
molasses and glucose are hygroscopic. These sugars not only help to retain
moisture but also impart a characteristic flavour to the product. Sugars
lower the caramelization point of the batter, allowing the cake crust to col¬
our at a lower temperature.

Shortening
Shortening for cakes should have good creaming properties, a neutral
flavour and odour. It should have excellent emulsifying properties and should
be white in colour. It should be elastic when used at temperatures between
21.1° and 23.9°C. Butter is considered to be best of all baking shortenings
in view of flavour. The creaming quality of butter is rather poor. Cakes made
with butter are generally lower in volume and have a coarser grain than
those made with a high quality shortening with good creaming characteristics.

356
 CAKES, COOKIES AND PASTRIES

For this reason some bakers use part butter in formula for the flavour it
contributes, and part shortening for increase in volume and finer grain.
Shortening also helps to retain moisture in the finished cake.

Eggs
Eggs and flour form a skelton which acts as support to the framework of
a cake. Fresh eggs have pH 7.0-7.5 and if allowed to stale the pH can change
to a low acid condition which will throw the leavening action of the formula
out of balance. Eggs also contribute moisture, flavour and colour to the
product in which they are used. Beating of eggs is very important. They
should be beaten so that they will hold a fairly good crease. This is made by
running a pallet knife through the beaten mass. Lecithin in yolk gives the
yolk-emulsifying properties.

Milk
Milk when used as dry milk solids adds richness and structure to cake.
The milk sugar lactose regulates the crust colour. Milk solids improve the
flavour and are good moisture-retaining agents. The water in liquid milk
contributes to the eating qualities.

Water
Water regulates the consistency of the batter. It also develops the pro¬
tein in the flour which acts to retain the gas from the baking powder. The
water also acts as a leavening agent, creating vapour pressure when the
internal batter temperature reaches 208°F (68.6°C) during baking. Water
adds moisture to the cake and in that way regulates the eating qualities of
the finished cake.

Salt
Salt is one of the cheapest ingredients. It has the property of bringing
out flavours. It helps in palatability of baked products and, therefore, should
be used with good judgement. It also lowers caramelization temperature of
cake batters and aids in obtaining crust colour.

Flavour
Due to the variations in strength of flavour it is not possible to set any
given amount to be used. It is much better to use a small amount of good
flavour than to load up the cake with a poor flavour. Flavouring ingredients
are of 3 basic types, i.e. spices, extracts and emulsions. The spices are
granular powders of roots, bark, seeds and blossoms of aromatic plants.
Extracts are alcoholic solutions containing aromatic flavours. Emulsions
are colloidal systems of volatile, essential oils dispersed with water and sta¬
bilized by gum plants.

357
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Leavening
Cakes are leavened in 3 ways, i.e. by incorporating air during mixing,
by use of chemical leavening agents and by vapour pressure created in the
oven. The manner of leavening depends on the type of cake being made in
regard to richness of formula, consistency of batter and baking temperature
(U.S.Wheat Associates, 1988).

Sponge cake
Sponge cakes depend mainly on the whipping of eggs for their lightness
or aeration. This lightness is produced by a thorough beating of the eggs
which causes formation of air bubbles. Due to heat, air and moisture in
these, bubbles expand during baking, causing the rising action. There are 2
types of sponge cakes—one which contains eggs, sugar, flour, salt and fla¬
vour and is known as a straight sponge. The other type contains the ingre¬
dients of a straight sponge and milk, shortening, water, leavening, etc. and
is known as short sponge.
Eggs are the most important ingredients in the sponge cakes, therefore
great care must be taken in their selection. They must be of good quality,
fresh and of a pleasing flavour. Duck eggs do not produce very satisfactory
results. It has been found that when eggs are heated at 37.8°-48.9°C they
will produce the best results. Care must be taken that eggs are not over¬
heated, to avoid coagulation and production of an inferior product. Sugar
has a mellowing or tenderizing effect on the cell structure of the cake and
when too high a percentage is used the cakes will sag in the centre or fall.
Granulated sugar gives best results. Equal parts of egg and sugar should be
used for beating purposes. Any excess sugar should be either dissolved in
the liquid or may be replaced by powdered sugar and sifted with the flour.
When high sugar content is used a sugary crust develops. Therefore, dis¬
solving most of the sugar will help eliminate this trouble. Soft bleached flour
produced from soft wheat is generally used in the manufacture of sponge
cakes. The colour of the flour though not important should be preferably
white. In order to eliminate flour pellets in the cake, it is best to sift the flour
just before adding it to the beaten eggs-sugar mixture.
Shortening provides better eating qualities to the sponge cake. How¬
ever, shortening has a mellowing effect on the cells structure of the cakes
and when used in large quantities will produce a cake lacking volume. There¬
fore, correct amount should be incorporated. When shortening is not incor¬
porated properly streaks will be found in the cake. These streaks will give
the cakes an off colour. Leavening and flour should be thoroughly sifted
together so that they will be well blended. At higher altitudes it is necessary
to decrease the amount of leavening agent. If the cakes contain a large
percentage of acid, a coarse porous cell structure will result. Sponge cake
batter breaks down readily on adding flour or other ingredients. Great care
must be taken not to mix any more than absolutely necessary. When the

358
 CAKES, COOKIES AND PASTRIES

batter is overmixed it breaks down, resulting in a tough cake which will

draw away from the bottom. Likewise, undermixing results in a cake with
low volume and rough texture. Therefore, sponge cake should be mixed
enough, so that the ingredients are incorporated smoothly and evenly. Ad¬
dition of moisture to sponge cake improves their keeping and eating quali¬
ties, but when used in excess, the cake lacks volume and may even collapse
while baking. The flour used should be of good quality. The amount used
must be measured carefully to produce uniform results. All ingredients should
be closely checked for off- flavours. Most bakeiy ingredients absorb odours
readily and, therefore, must be carefully stored away from any source of
contamination. Many bakers overlook the possibility of boxes and wrappers
having an off odour. It is wise to investigate this factor. Quality fillings should
be used at all times. The keeping quality of these fillings is of great impor¬
tance and should be closely checked.
When the pans are greased too heavily the fat will run over the sides of
the cake on to the top crust producing an unappetizing appearance. Batter
should be placed in pans ensuring that there will be no air trapped under¬
neath the batter. Due to heat air expands resulting in hallow spots under
the cake. Trapping the pans lightly will reduce this source of trouble. Sponge
cakes both straight and short are baked at a higher temperature ranging
from 187.8°-232.2°C, depending on the type and size of the cake.
When cakes come out of the oven they are sterile as far as mold is
concerned. Mold infection is due to contamination after baking. Mold spores
are present in the air at all times and their concentration should be kept as
low as possible. Cleanliness is very important in eliminating this source of
trouble. Cake should not be cooled in a draft or by the blowing of air by fan,
as this will cause excessive drying out, unless draft is carefully controlled.
Cake should be cooled so that air is able to circulate freely above and beneath
them. When cakes are cooled improperly the top ciqist will become sticky
and will peel off. Good boxes and wrappers also keep the cakes from drying
out fast or excessively. All pans used be washed and rinsed thoroughly, so
that they will be free from foreign odours. Many bakers overlook this impor¬
tant point. Cleanliness pays dividends.

Fruit cake
The term fruit covers wide area depending on the amount of fruits to be
used. This amount of fruits could vary from 30 to 300% in relation to the
weight of the batter. Whereas the fruit cake will not have more than 30%
fruits in relation to the weight of the cake batter. The difference between the
fruit cakes and cakes with fruits is that in fruit cake the batter separates
the fruit from coming intimately in contact with each other and acts as a
filler, while in cakes with fruit the pieces of fruits are scattered throughout.
The type and amount of fruits and nuts to use will depend on several factors,
mainly the price and ready availability. The cakes containing larger per-

359
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

centage of fruits will definitely be of better eating quality than the one with
less fruit. But at the same time higher the percentage of fruits mixture,
lower will be resultant volume than a cake of the same weight with a smaller
percentage of fruit because of the dead weight of the fruits in relation to the
lower percentage of cake batter (Dean et al 1963).
There are several types of fruits and nuts which could be used in the
preparation of a fruit cake. To prevent spoilage of fruits during transit and
storage these are processed. Fruits like raisins, dates, sultanas are pre¬
served by drying, while other fruits like pineapple, peaches, apples, cherries
and orange peels are saturated with sugar to prevent spoilage. These are
termed as glazed or candied fruits. Generally moisture in fruits is approxi¬
mately 20% or less compared to 32% moisture in cake crumb structure.
Therefore, almost all fruits should be soaked before use to soften and ten¬
derize their skins, to remove the hard sugar coating and to cause them to
absorb sufficient moisture for improved eating qualities. Soaking not only
improves the quality of fruit but also increases the yield. Moreover, the
fruits which have been soaked previously do not draw moisture from the
cake structure and keep the product in good condition for a longer time. The
dried fruits which have been soaked in moisture should be thoroughly drained
before using. Nuts should not be soaked as they soften and become rubbery
and their colour will also be affected adversely. The flour used for making
fruit cakes should have enough strength to carry a high percentage of fruits,
sugar, moisture and other materials. A high grade cake flour containing
7-9% proteins is recommended. This type of flour will help the fruit from
sinking. Avoid the dusting of fruit mixture with flour. Dusting of the fruit
will give the cake poor inside appearance. The best results are obtained
when the ingredients are used at a temperature which will give the finished
batter temperature of about 21.1°C. The shortening used be kept at 21.1°C
and the milk and eggs at about 15.6°C. Shortening used for cake work
should have good creaming qualities, neutral flavour and odour, and excel¬
lent emulsifying powers. (Emulsification is the process of blending together
fat and water solutions of ingredients to produce a stable mixture which will
not separate on standing). Emulsification helps produce cakes which are
more tender, of finer grain, moist and with less tendency to dry out. A small
percentage of butter can be used along with the shortening. Due to the
presence of higher percentage of fruits of various types, nuts as well as
extracts, it may be quite hard to detect butter flavour, however. The leaven¬
ing content in fruit cakes is generally low. The volume is obtained through
the air and moisture incorporated during the mixing of the batter.
The fruit cakes generally are decorated with various designs, made with
nuts and fruits. Whether this should be carried just before the baking or
after finishing baking is a matter of choice. But preferably it should be done
soon after the cake is out of the oven. It will prevent the nuts from getting
scorched and discoloured and the fruits will stay soft. It also produces a

360
 CAKES, COOKIES AND PASTRIES

lively fresh appearance. Fruit cakes may be washed immediately after baking
with a glucose preparation for extra gloss. The glucose preparation is made
by boiling one part of glucose and one part water together and using it while
cakes are still hot as they are removed from the oven. If the cakes are washed
with glucose solution and then decorated at once the fruit and nuts will
stick on very nicely. Another wash with glucose solution after the design is
placed will enhance the appearance.
Before baking is done it is always better to check whether the batter is
well packed in the pans so as to avoid holes in the cakes and unfilled corners.
It is considered good practice to moisten the back of the hand and smooth
the surface of the cakes before baking. This will eliminate the possibility of
fruit, such as raisins exposed to the direct heat to caramelize and cause an
objectionable taste.
Fruit-cakes should be baked at a temperature of 229-330°F depending
on the richness of the formula and the size and shape of the cake. If oven is
not equipped to inject steam during baking, place the cake pans in a shallow
tray containing water just sufficient enough to cover one-fourth of the height
of the cake pan. This will not only help create steam in the oven but will also
prevent the charring of the fruit-cake at the bottom as well as on the surface
during the prolonged baking. Trays with water should be removed when the
cakes are half done. Presence of steam will produce a cake having softer
crust, prevent excessive drying. In scaling allow 75 g additional batter for
baking loss to each kg of batter. A good quality fruit-cake should not crum¬
ble even when thinly sliced and should be moist for good eating qualities.

Angel cake
The basic ingredients of angel food cake are flour, sugar and egg. The
other ingredients are salt, flavourings and cream of tartar or an acid. The
proportion of sugar in the cake mix is high because no other tenderizer is
used. Sugar interferes with gluten development and thus tends to produce
more tender and fragile cake. Sugar also has a stabilizing effect on egg -
white foam and allows more beating without the over coagulation of the
white proteins. Cream of tartar is added to egg-whites for angel food cake as
it makes the cake whiter, finer in grain and more tender than it would be
without it.

Chiffon cakes
Chiffon cakes usually contain a larger proportion of egg than shortened
cakes and an oil. The cake is prepared by sifting together the dry ingredi¬
ents followed by the addition of the oil, egg-yolk, liquids and flavourings and
the whole mixture is well-blended. The whites are then beaten with the
cream of tartar until the peaks just bend over; the batter is carefully but
thoroughly folded into the beaten whites. The cakes are then baked in the
usual way (Shakunthala and Shadakshanaswamy, 1987).

361
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Off flavours in cakes: causes and prevention

Flavour and taste are the most outstanding characteristics of a good
cake. The flavour and taste depend on the ingredients, proper pan care,
storage and packaging, and use of icings and fillings.
Ingredients
Most of the cake ingredients will absorb foreign odours. Therefore, they
must be stored carefully away from all possible contamination. In a store
room the strong flavoured ingredients should be kept in an air-tight con¬
tainers to avoid intermingling of flavours. A low-grade baking powder will
have a residue which has an objectionable flavour. In chocolate cakes bak¬
ing soda is used to produce red brown colour. The effect on the flavour is not
objectionable if a correct quantity of soda is added.
Proper pan care
Dirty pans are the causes of off flavour in cakes. To overcome this defect
pans should be washed after each baking. Off flavour can also be caused by
improper pan grease.
Storage and packaging
Avoid storing cakes in mouldy and musty cabinets. The show-case should
be spotlessly clean and odourless. Foreign odours may be due to the wrap¬
pers or boxes used for packing. Varieties of cakes soon after baking should
not be cooled on the same rack.

ICINGS AND FILLINGS

Icing may mask a number of faults. But do not ice the cakes which are
overbaked or burned. Icings should be made fresh each day. The use of low-
grade jams and jellies will also cause off flavours. Mouldy or rancid left-over
cake crumbs when used will not improve flavour.
Besides the off flavours the baker should recognize the cake faults such
as shape faults, structural faults, texture faults, crust faults, colour faults
and miscellaneous faults and find the solutions by a process of eliminating
the possible causes.

Icings
Icings are sweet coverings—plain or with vivid pattern in which sugar is
the main ingredient. Type of an icing depends on the materials used in the
preparation as well as the method of mixing. There are various types of icing
which can be classified under 2 groups:
1. The icings which are like flat icings including a fondant are melted by
heat and when cooled get set to a firm coating. Fondants contain a high
proportion of small sugar crystals that partially dissolve on warming and
recrystalize on cooling.
2. The highly aerated icings composed of a creamed mixture of shorten¬
ing, confectioners sugar, water, salt, flavour, eggs and milk powder. These

362
 CAKES, COOKIES AND PASTRIES

are more suitable for spreading and piping where aeration or whipping is
used to produce icings of stiff, non-flowing consistency.
The basic ingredients of icings are sugar, shortening, dried milk powder,
eggs and stabilizers.

Sugar
Various types of sugars can be included in the preparation of icings,
powdered sugar or confectioners sugar, being the most common. Invert sugar,
corn sugar and glucose are also used in flat icings to control the size of
sugar particles.
Shortening: Emulsified or hydrogenated shortening is usually used in
cream type icings. Shortening should be neutral in taste and flavour. Butter
is also used in combination with shortening due to its characteristic flavour.
Butter alone cannot be creamed to give an equal volume as shortening.
Dried milk powder: Milk powder provides a structure to the icing as well as
enhances taste and flavour of icing. It also helps to absorb moisture. Fresh
milk is not recommended due to its perishable nature. Milk powder should
always be sieved along with sugar to avoid the lumps. In case lumps are
present it will be difficult to pipe the icing with a fine nozzle.
Eggs: Eggs should be fresh. They constitute to the volume, taste and
flavour of the icing. They should be blended carefully with creamed mixture
to avoid curdling.
Stabilizers: Various types of stabilizers are used in icing, mainly to ab¬
sorb excess moisture. By holding moisture a stabilizer can avoid sugar crys-
talization. It can also eliminate stickiness during hot humid weather.
Stabilizers may be vegetable gums, tapioca starch, pectin and wheat or corn
starch. Water is used to dissolve sugar in preparation of icings. Water also
permits the boiling of sugar without burning. Flavours and colours should
be used wisely and carefully. Salt, when used in small quantities, supple¬
ments and enhances the taste and flavour of other ingredients.
Flat icings
Flat icings are the combination of confectioners sugar, water, corn syrup
and flavour. All the ingredients are to be mixed to a thick paste consistency
and warmed to about 43.3°C. To avoid direct or over-heating of icing, a
double boiler method of heating should be used. Many times due to over¬
heating an icing loses its gloss after cooling. Whenever flat icing gets thickened
after its make up, it should be rewarmed to bring to the correct consistency
required. Do not soften the icing with water before the icings are reheated,
otherwise it will cause stickiness in icings and also causes difficulties in
setting. When through with immediate use of a flat icing, it should be covered
with a thin film of water to prevent crust formation. Fondant is prepared by
using 2 parts sugar, 1 part water and a pinch of tartar cream.
The sugar and water are placed in the pan and are heated. They should
not be allowed to boil until the sugar is dissolved. When the temperature

363
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

reaches 107.2°C, add the cream of tartar dispersed in little water. No stir¬
ring should be done when the temperature reaches 107.2°C. During the
boiling period the side of the pan should be carefully washed down to re¬
move sugar crystals formed on the sides of pan. The scrum should also be
taken off. Boil until the moisture reaches 115.6°C, i.e. forms a soft ball
when dropped into cold water. Remove from the fire and pour over a marble
top. Allow to cool to 37.8°C. After cooling heat the mixture until it starts
turning cloudy white, and finally into a stiff white creamy mass. Knead it till
it is moulded into a smooth plastic condition. It can be stored in a cool
place, properly covered. When required for use fondant is placed in a pan
and carefully heated, preferably over a double boiler to a temperature of
about 43.3°C. It should be made into pouring consistency by adding water
or stock syrup (stock syrup is prepared by dissolving 100 g sugar to 50 g
water and heated without stirring up to 104.4°C. Allow to cool. By using
stock syrup, fondant will retain the gloss. Pour the fondant over the cake
and allow it to set.
Creamed icings
Creamed icings are prepared with fat, confectioners sugar, water, salt,
flavour, eggs and milk powder. The general procedure is to cream dry ingre¬
dients with shortenings. The beaten eggs are added gradually. The water
and flavouring are added in the end, blending well. Creamed icing should
be stored in a cool place and should be kept covered to avoid crust forma¬
tion. Creamed icings have tendency to lose their smoothness after a long
storage. In such cases icing will not have the ability to spread smoothly and
evenly. In order to restore their smoothness they should be placed in warm
water bath and creamed well until smooth. Do not over heat to avoid fat
from melting away. Icings also help in retarding the staleness of the prod¬
uct. This depends mainly on the type of icing used. Flat icings which do not
contain appreciable amount of shortening will have a tendency to absorb
moisture from the cake. Creamed icings are much more effective in control¬
ling the rate of staling.
Butter icing
Ingredients are: butter, 250 g; icing sugar, 500 g; vanilla, 1 teaspoon
and colouring as desired.
Method: Cream butter to a smooth consistency. Add icing sugar little at a
time and cream. Finally add vanilla and colour as desired. For making the
cake the consistency of icing should be soft, whereas for piping it should be
stiffer.
Royal icing
Ingredients are: egg-whites, 2; icing sugar, 450 g; Cream of tartar, one-
fourth teaspoon and colour and flavour as desired.
Method: Add cream of tartar to egg whites and beat gradually. Add icing
sugar gradually and continue beating. Add colour and flavour as desired.
Consistence for spreading should be softer, whereas for piping it should be
stiffer.
364
 CAKES, COOKIES AND PASTRIES

Precautions: Egg whites should be separated neatly. Minute presence of

egg yolk will spoil the icing. Utensils in use should be absolutely grease free
and dry. Egg whites should be rested for sometime (3-4 hr) before using
them.
Frosting
Ingredients are: Gr. sugar, 450 g; water, 150 g; egg-whites, 2; colour
and flavour as desired; and cream of tartar one-fourth teaspoon.
Method: Boil sugar and water exactly as for fondant to 115°C or to soft
ball consistency. Beat the egg-white with cream of tartar to a stiff peak. Add
syrup in a trickle and continue beating up to the start of setting. Pour on
cake quickly before it sets completely.

Cookies
Cookies are made by the same general methods as are used in making
conventional cakes. The ingredients are also similar to those of cakes. The
main difference is the decreased amount of liquid in cookie dough. The
other differences are the increased amount of fat and egg and the smaller
amount of leavening agents used. There are many varieties of cookie recipes
and the different types of cookies are prepared as follows.
Drop cookies
These are made by dropping the mixture from a spoon onto a cooky
sheet and baked in an oven at 190°C for 10-15 min. until nicely browned.
Bar cookies
They are also known as sheet cookies, and are baked by spreading the
dough (similar to that of drop cookies) in a shallow pan. The individual bars
are cut after baking.
Rolled cookies
Rolled cookies are made from refrigerated stiff dough. The dough is
rolled and cut into the desired shapes and baked.
Meringue cookies
Such cookies are made with dough prepared by beating egg-whites un¬
til stiff and adding sugar slowly. Other ingredients are folded in and the
batter dropped on a sheet and baked.
Sponge cookies
They are made like meringue cookies, using the whole egg rather than
just the egg-white.

Pastry
Pastries include a number of baked products made from doughs con¬
taining medium to large amount of fat. These include pies, which are very
popular in the United States, puffy pastries, Danish pastries, etc. The success
of pie making depends mainly on the quality of crust.
Plain pastry is leavened primarily by the steam produced during baking.
The ingredients in pastry are flour, salt, fat and water. Generally, the pro¬
portion of flour, fat and water is 6:2:1. This mixture gives a tender pie crust.

365
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

If a less rich crust is required, a mixture of flour and fat in a 4 : 1 ratio is

used. Generally, all-purpose flour is used for plain pastry. Butter, margarine
and hydrogenated vegetable oils are used as shortenings. Oil may also be
used but the pastry will be crumbly and greasy.
In the preparation of the pastiy, flour and salt are mixed after which
the fat is cut into the flour. Water is then gradually added with stirring and
worked into the dough. The dough is shaped into a ball, flattened into a
circular shape, and transferred to a pie pan and baked in a hot oven at
218°C until the surface is delicately browned. Then the filling is placed on
the crust.

Pizza
Pizza is consumed in place of complete meal, as it provides all nutrients
needed by an individual. It is a baked product with all vegetables (Salunkhe
etal, 1986).

For dough
Plain flour (all purpose) (V/2 cup) 250 g
Dried yeast 5g
Warm water 30 ml
Salt 5g
Baking powder 5g
Egg 50 g
Milk 45 ml
Vegetable oil 30 ml
For filling
Onion (chopped) 1 large
Garlic (chopped) 10 g
Cloves (powdered) 10 g
Tomatoes 250 g
Tomato puree 30 g
Salt + pepper powder 10 g
Cheese (sliced) 150 g
Any vegetable (eg. carrot) 250 g
Black olives 6 large
Olive oil 5 ml

Method: To make the dough:

• Dissolve the sugar in warm water.
• Mix yeast in warm water and sprinkle the water on top.
• Leave in a warmish place for 10 to 15 min. or until frothy.
• Sift the flour and salt and baking powder thrice.
• Cream butter and mix with flour.
• Mix dough with the yeast liquid, add a little extra flour if the dough
is sticky.
• Knead for 10 min. or until the dough is smooth and elastic. Keep it
in an oiled bowl. Cover with butter paper and leave it to rise to
double the size.

366
 CAKES, COOKIES AND PASTRIES

• Turn-out onto floured surface then knead lightly until smooth.

• Roll out into a 0.63 cm thick circle and arrange on an oiled baking
tray.
• Brush with olive oil and cover with slices of tomato and other veg¬
etable slices.
• Sprinkle garlic, cloves powder. Place olives, onions, and top with
slices of cheese. Sprinkle pepper and salt.
• Bake at 230°C for 25-30 min. in an hot oven.
• Serve while still warm (Sonia Alison and Ulrike Biefelet 1973).
Types of pizza: Ham pizza, pizza with mushrooms and olives, pizza with
salaami, small pizza, and pizza Neapolitan.

REFERENCES

Dean, K.D, Edwards,N.E. and Russel, C.A. 1963. An Introduction to the Physics and Chemistry
of Baking. Maclaren & Sons Ltd, London.
Shakunthala, N.M. and Shadaksharaswamy, M. 1987. Foods—Facts and Principles, pp. 275-80.
Wiley Eastern Limited, New Delhi.
Sonia, Alison and Ulrike Biefelet. 1973. The Gourmet’s Guide to Italian Cooking. Octopus Books
Ltd, London.
Khandari, L.R. 1988. Bakers Handbook on Practical Baking 902, U.S. Wheat Associates.

LEARNER’S EXERCISE

1. What are the factors influencing quality of pastry?

2. Explain the effect of temperature of ingredients, when mixed, upon the texture and ten¬
derness of pastry.
3. Explain the role of various ingredients in cake making.
4. Write about type of cakes.
5. Why icing and filling is important in pastries?

367
25. Microwave
cooking

M icrowave cooking takes place because certain types of molecules are

capable of absorbing electromagnetic radiation in the radio-frequency
range. Water, the major constituent of most foods, is composed of such
molecules. Microwaves are highly penetrative and the absorption of radio¬
frequency energy within food causes a rapid rise in temperature throughout
the material and thus produces a relatively uniform cooking effect. Materi¬
als such as glass, ceramics, plastics and paper, from which containers and
packaging of foodstuffs are commonly made, do not absorb radio-frequency
energy so that microwaves pass straight through them without making them
hot. On the other hand, metals reflect microwaves and cannot be used in
microwave cookers, although recent development in the design of ovens and
packaging suggest for frozen foods use may soon be able to be accommodated
in the technique of microwave processing (Magnus Pyke, 1981).
Two-wave frequencies are commonly used: for domestic ovens, 2450
MHz is preferred, whereas in industrial applications, 896 MHz is considered
more suitable. The product to be heated is placed in an enclosed oven and
microwaves, generated by special oscillator tubes, are guided on to it. The
penetrative power of the radiation allows cooking to occur rapidly through¬
out the product unlike conventional ovens where cooking takes place from
the outside of the food inwards and rates of heat transfer are relatively slow.

Domestic and commercial catering applications

The most useful application of microwave cooking under domestic con¬
ditions and for those concerned with food service, has been in heating fro¬
zen cooked meals or snacks for consumption. A frozen meal, for example,
can be heated to serving temperature in lV£-4 min. in a microwave oven
compared with 20-30 min. in a conventional oven. Where frozen foods are
popular, the use of the microwave oven has grown rapidly. It has been esti¬
mated that in the United States 50% of all homes and 80% of all catering
establishments had microwave ovens.
The cooking of fresh foods, particularly meats, in microwave ovens suf¬
fers from the disadvantage that microwaves cannot brown foods. This has
to be done separately under a grill or in an oven and reduces the conven¬
ience of using microwaves. Attempts are being made to overcome this by
incorporating within ovens a browning element or a special heat sink con¬
structed of absorbing material on which the food may be placed. Beef roasts

368
 MICROWAVE COOKING

or poultry may be cooked in 6-7 min., although this must be followed by a

‘resting’ period of 15-20 min. before carving to allow heat to penetrate evenly
throughout the mass.
It is expected that the rapid growth in use of microwave ovens will force
food manufacturers to develop products especially prepared and packaged
for microwave cooking. New opportunities and challenges exist, in particu¬
lar, for the frozen food industry and the first signs of these being taken up
are already evident in the form of frozen pizzas, pancakes and popcorn.

Industrial applications
The penetrative power of microwaves and their ability to raise tempera¬
tures rapidly in frozen foods has led to the widespread use of microwaves to
assist thawing of frozen ingredient raw materials in the food industry. Meat,
fish and poultry are normally used by the industry in the form of frozen
25-50 kg blocks. These have to be removed from frozen storage to be tempered
at 0°C for several days before use. In contrast a 20 cm-thick block of frozen
beef weighing 50 kg can be tempered from -15°C to -4°C in 2 min. by micro-
wave heating. It is then ready for processing. The commercial advantages of
flexibility, energy-saving and the saving of refrigerated and frozen storage
space are readily apparent. Frozen ingredients are not thawed completely.
Because water absorbs energy more quickly than ice does, the first part of a
block to thaw would get hot quickest, so that before long water could be
boiling at one place adjacent to another place which was still frozen.
Other industrial uses of microwave heating are:
• Production of skinless sausages
• Potato crisp manufacture
• An aid to freeze-drying and air-drying where case-hardening in the
final stages of drying can be avoided
• Baking of biscuits and cakes
Cooking of food results in improvement in flavour, texture and appear¬
ance, and this makes the food more palatable and easily digestible. Most
foods in the raw state contain harmful microorganisms and they are destroyed
during cooking (Mudambi and Rajagopal, 1960).

Method of cooking
Heat may be transferred to the food by conduction, convection, radia¬
tion or by the energy of microwaves (electronic heat transfer).
Conduction: It is a method of transfer of heat by contact
Convection: Convection is the transfer of heat as a result of the flow a
liquid or gas travelling from the hotter to less hot part of oven or sauce pan.
Radiation: It is the emission of heat in the form of waves from hot objects.

MICROWAVES
Microwaves are a form of electromagnetic radiation similar to radio, televi-

369
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

sion, light and infrared waves.

Microwave cooking which was first recognized as valuable for cooking
food in 1947 it took 20 years for the microwave oven to become common
item on the market.

Operation and structure of microwave oven

Microwaves do not require any medium for transfer of heat in cooking.
The magnetary tube (electric instrument) is vaccum tube which can convert
electricity in electromagnetic energy radiation, (Muller and Tobin, 1980;
Shakunthala and Shadaksharaswamy, 1995).
In microwaves food is cooked by the heat generated in the food itself.
The frequencies for microwave heating came under the rules of the federal
communications commission, which has designated for frequencies 915,
2450, 5800 and 22,125 mc/sec. The majority of the microwave ovens of the
market today use 2,450 magacycles. The microwaves can be absorbed, trans¬
mitted or reflected when they impinge on substances. They pass through
paper, China glass and some plastic without absorption and are reflected by
metals and absorbed by food. The structure of microwave oven is given in
Fig. 62.
When food is kept in the cavity of a microwave oven for cooking, micro-
waves, generated by the magnetron, strike the food and the metal walls of

Fig. 62. Structure of microwave oven. 1, Door release button; 2, oven window; 3. door safety lock system;
4, oven air vents; 5, control panel; 6, identification plate; 7, glass tray; 8, roller ring; 9, wire rack

370
 MICROWAVE COOKING

the oven. Microwaves that strike the metal wall are reflected and bounce
back, so that they disperse through the oven. This is important for accom¬
plishing a uniform heating of food. Microwaves penetrate food to a depth of
2.5-7.5 cm. Up to this limit of penetration of the microwaves, the food gets
heated and cooked. Thus, food will heat up inside and outside at the same
time, to the depth of their penetration and the portion of food beyond it will
be heated more slowly by conduction. Food for cooking in a microwave oven,
should be kept in containers that transmit the microwaves and should not
absorb or reflect them.This is achieved by using paper containers, such as
paper plates or cups, plastic utensils glass or Chinaware which do not contain
metallic substances.
It requires skill and experience to use the microwave ovens successfully.
It cooks foods in half and one-third the time of an electric oven.
Food industiy in the recent years has witnessed the emergence of a
microwave oven as a substitute to thermal oven for a number of food-manu¬
facturing processes and products. The modern tempo of life as well as the
increasing number of working women require simplified routines and stand¬
ardization of foods with lesser preparation time and convenience in usage.
Microwave oven is a boon to the consumers who consider their time too
valuable to be wasted in waiting for food to be cooked, heated or thawed to
room temperature. Due to this advantage, practically it has become a house¬
hold item in the west and this trend is now being adopted in the Indian
society.

Advantages of microwave cooking

Microwave cooking can be used in 3 ways, i.e. cooking the raw ingredi¬
ents, reheating of prepared refrigerated food and reheating of prepared food
from the freezer.
The main advantage of a microwave oven over the conventional oven
(electric and gas oven) is its high thermal efficiency in converting the energy
in electricity into heat in the food. Other advantages include:
Speedy: Microwave cookers heat food more quickly than any conven¬
tional oven and are economical in that they use less energy.
Clean: With microwave cooking there is no risk of foods burning on to
the cooker walls as they do not become hot in the way that the surfaces of
a conventional oven do. In addition, most foods are cooked covered and so
remain in their containers.
Smell free: Because food is contained within the cooker cavity (and usually
also in a covered dish), smells are kept to a minimum.
Less washing up: It is often possible to microwave food in a serving con¬
tainer or on the plate from which it is to be eaten. This reduces the kind of
washing up required when saucepans and metal oven dishes are used.
Thawing: Thawing can be done quickly in a microwave cooker, saving
hours in the fridge or kitchen and removing, the need for too much forward

371
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

planning. One can decide, a short time before a meal, about eating of currently
frozen food by one or many people.
Nutritionally sound: Many foods retain more nutrients than when cooked
conventionally because the cooking times are so short and there is litttle or
no added water, particular examples are fish and vegetables.
Easy-to-use: Once the controls and cooking techniques are mastered,
microwave cookers are extremely easy-to-use.
Cool: Unlike conventional ovens, microwave cookers do not produce ex¬
ternal heat and so can be used anywheare that is convenient, such as a
dining-room or bed-sitter.

Disadvantages of microwave cooking

Though microwave coking has many advantages, it also has certain
limitations.
1. Because of the speed and the way in which microwave energy cooks,
food cooked in a microwave cooker will not be brown, with the exception of
poultry that requires more than 20 min. There will be brown but they will be
crisp and will look a little different from conventionally cooked dishes.
2. High initial cost.
3. The short cooking time does not allow flavours to develop and this
may make food unacceptable.

Factors affecting cooking times

The time that food takes to cook, thaw or reheat in a microwave cooker
will vary according to the following factors.
Composition: Foods with a high moisture content will take a longer time
to cook or reheat than dried ones, whereas those which are high in fat or
sugar, cook or reheat more rapidly than those which are low in these ingre¬
dients. Jam, marmalade and other sugary coatings on cakes, puddings or
tarts will heat up much more quickly than the rest of the food and can
become extremely hot so do not attempt to eat them straight from the mi¬
crowave cooker.
Density and texture: Light, open-textured foods will cook and reheat more
quickly than more dense items. For example, minced meat will cook more
quickly than the same weight of solid meat. The denser the food, the longer
it takes to cook.
Size of food: Several small pieces of food will cook more quickly than the
same amount cooked in one piece. A joint requires longer cooking time if left
whole than diced meat but with small pieces it is important to make sure
that they are cut to the same size so that they cook at the same speed.
Quantity of food: The larger the quantity of food the longer it will take to
cook, but doubling the quantity does not necessarily mean doubling the
time. Similarly, a reduction in the amount of food calls for a reduction in the
cooking time.
Temperature: The colder the food the longer it will take to heat up.

372
 MICROWAVE COOKING

Cooking utensils: The ideal micro-ovenable package should have the fol¬
lowing attributes (McGraw-Hill, 1979).
• Strong and rigid as metal
• Light in weight
• Resistant to high thermal oven temperatures
• Completely transperent to microwaves
• Inexpensive
Ceramic is often designed specially for microwaves. Standard glazed
household china and pottery can be used for microwaving. Heat resistant
glass and plastics (polypropylene, polysulfone, thermostat polyester) can
also be used.
Round containers are preferable to square and oval ones because they
lack the corners and narrow ends in which microwaves can cluster and
overcook food. Ring moulds are particularly good as they allow microwaves
to reach the food surface from the inner ring as well as the outside. Straight¬
sided dishes allow food to cook more quickly than those with sloping sides
and shallow dishes provide a bigger food surface area for the microwaves to
penetrate.

MICROWAVE ENERGY AND FOOD PRESERVATION

Microwave energy is gaining increasing importance as an energy-saving,

rapid, and effective cooking and heating method for food preparation in
homes, institutions, and commercial establishments. Microwaves, such as
those used in cooking and processing foods, are part of a broad spectrum as
electromagnetic radiation which includes radio waves, microwaves, infrared
radiation, visible light, ultraviolet radiation, X-rays and gamma-rays. An
understanding of the dual nature of electromagnetic radiation is necessary
for an understanding of the processes of emission, transmission and ab¬
sorption of microwaves, which is in turn necessary for an understanding of
the processes and phenomena that is important in the use of microwave
energy radiation as a source of energy for heating and food processing
(Swanson, 1984).
The usual process by which food is heated involves heating the outside
of the food by convection with heated oven air. These oven heating sources
heat a very thin layer at the surface of the food, while the interior of the food
is heated by conduction from a heated surface. The thermal conductivity of
foods is not high; thus, it takes quite a long time for the interior of the food
to reach cooking temperatures. When the food is heated by microwaves,
energy is absorbed uniformly throughout the food and the time necessary
for the food to reach cooking temperatures is reduced. Microwaves heat by
causing the alignment of polar molecules within the food to change rapidly,
thus generating heat uniformly which cooks the food.

373
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Microwave blanching
On the basis of what is known about microwave blanching, it is ques¬
tionable if microwave or combination blanching with microwave energy and
steam would be significantly better than steam blanching of vegetables.
Process time is not reduced to any great extent and the cost is substantially
higher. Microwave blanching would appear to have some potential advan¬
tage in the blanching of products of rather large cross-sections such as
whole potatoes, corn-on-the-cob, Brussels sprouts, broccoli, and the like,
where over-cooking of the outer surface would be minimal and a much
more uniform texture would be possible. Microwave blanching of potato
strips in the production of commercial french fries is not satisfactory due to
case hardening the formation of a leathery layer on the outside of die potato
strip during blanching. The problem with microwave blanching is that
evaporative cooling occurs at the product surface and prevents tempertures
great enough to inactivate surface enzymes in reasonable process times.
When saturated steam is applied simultaneously, this deficiency is correct.
The prospects of in-package balanching appears to be remote. Quality would
undoubtedly suffer because cooking and freezing would be hampered.
Pasteurization of bread and cakes to inactivate mould spores has been
markedly successful. Promising results with microwave pasteurization of
ham and other precooked foods are available but have not been implemented
commercially. Good results have been obtained with pasteurization of milk,
beer and other non-viscous beverages, but it is unlikely that microwave
heating can compete economically with the very efficient pasteurization
methods in commercial use for these beverages.
Microwave heating does not appear to be economical for sterilization or
complete dehydration of foods, but is better suited for finish drying of small,
thin food products. The best known and largest commercial application of
microwaves has been in finish drying of potato chips, although many instal¬
lations operating in the United States have ceased. On a limited basis, re¬
markable advantages are reported from combining microwave with steam/
hot-air techniques in the commercial pre-cooking of meats. In conventional
factories, in pre-cooking chicken, product may loss 20% of its total weight
during oil frying, and in microwave the lose is much less.
Thawing of bulk frozen foods for industrial use often requires long pe¬
riod of time; consequently, microwave heating has long attracted interest
for this application. Microwave thawing of fish, meat and other products
presents a rapidly growing process. Detempering-defrosting of frozen food
block with microwave energy is uniform and when applied on a moving belt
generally taken less than 5 min. This process also has drawbacks. Micro-
wave defrosting on a conveyor requires large capacital investment and must
be carefuly controlled. There is no drip loss, bind loss, or loss of colour or
flavour. The processor is able to match product quality to each order; thus,
there is no need to plan ahead and no danger of being caught by change of

374
 MICROWAVE COOKING

plan. Furthermore, the food material is brought rapidly to temperature and

is warm for a short period, which minimizes microbial growth which is im¬
portant to product quality. Sanitation thus is greatly improved.

Microwave cooking and nutrition

Microwave cooking and heating have many nutritional benefits. Reserch
results clearly indicated that microwave cooking was less harmful to vitamins
than cooking by conventional method. Thaimine and riboflavin are retained
better in meats, fish, and cake mixes. Microwave blanching had almost no
effect on the ascorbic acid content of many vegetables. Protein losses can be
substantially reduced in thawing and cooking if microwave defrosting and
cooking are used. Vegetables can be prepared with little or no water, and
there is little or no leaching, and more nutrients can be retained during
microwave cooking. In general, longer the food preparation time, greater the
nutrient losses; microwave food preparation is less time consuming. For
retail-size packages of frozen foods, microwave heating is as good or better
than the conventional method for retention of nutrients. Microwave cooking
will result in a greater percentage of available nutrient ingested and
presumbly a general improvement in our nutritional well-being.

Use of microwave heating in meat and fish processing

Unlike conventional heating which depends on transferring heat through
a temperature gradient being applied to an exposed surface area, micro-
wave power heats as it is dissipated in the volume of the material and is
therefore referred as a volumetric method of heating.
The heating effect per material volume is proportional to frequency,
square of electrical field strength and dielectric loss factor of the material
assuming that the majority of the heating effect is through dipolar.
The principal frequencies used internationally for heating are 2,450
MHz and 896-915 MHz, the lower frequencies giving greater penetration
depth especially at temperature below freezing point. Microwave generators
operating at 2,450 MHz are normaly restricted to outputs of 6 kw and their
heating-conversion efficiencies, viz. ratio of power converted into useful heat¬
ing effect of power supply to the generator, is in the range of 50-55%. Gen¬
erators using 896-915 MHz are normally built with outputs in range of
30-60 kw and having conversion efficiencies of 85%, making them more
acceptable in terms of running cost for most continuous heating process
(Everington, 1989).

Cooking
Continuous microwave cooking of meat and fish is generally applied to
convenience food processing whereby slices of meat are heated in gravy or
fish fillets in sauce. Other cooking applications have been in the production
of meat patties, which in some cases, the patties have been flash-fried in oil
before heating and in continuous cooking of sliced bacon (Osterdahl and

375
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Alriksson, 1989). Plants using microwave cooking claim greater yields com¬
pared with the use of conventional ovens.
Cooking with microwaves compared with the conventional method of
cooking, generally results in a lower average temperature, being obtained
due to the lack of an appreciable temperature gradient. A lower cooking
temperature and a shorter cooking time generally give a lower weight loss.
When comparing the cooking of 1.5 kg chicken in a continuous microwave
plant with cooking in a conventional oven, it was found that when using
microwaves, cooking to a temperature of 80°C, the weight loss was 15%.
When the temperature was increased to 85°C, the weight loss increased
between 22 and 23%, while at 87°C the weight loss became 30%. The weight
loss in the conventional oven was between 25 and 30% and this weight loss
would be normal in conventionally cooking chicken. However, with micro-
wave cooking chickens, the surface remains pale and if the chicken is not
being cooked for striping but being sold retail or whole, then they must be
passed after cooking for approximately 5 min. through a radiant heated
tunnel to brown the surface.
Chilled meat and fish dishes which are produced in microwavable con¬
tainers, as value-added convenience foods have experienced a rapid growth
rate in Europe in the past 2 years. The reason for this is that the consumer
perceives chilled foods as being fresh and, therefore, prefers them to frozen
dishes. The problem with chilled foods, however, is the short shelf-life of
4-5 days under chilled conditions of 4°C. Another concern is that the chill-
chain is subject to wide temperature fluctuation which would decrease the
shelf-life further. Chilled shelf-life can be extended to 3-6 weeks by pas¬
teurizing dishes in sealed microwavable trays where they are heated by
microwaves to 85°C and held at this temperature for approximately 2 min.

Sterilizing
In order to sterilize meat, it is necessary to raise its temperature into
the region of 132°C and this only becomes possible if the microwave appli¬
cator is pressurized during the heating and cooling period. Present meth¬
ods of pasteurizing convenience foods in microwavable containers use batch
retorts which are labour intensive and so a continuous methods using mi¬
crowaves is attractive. Techniques of field focussing have already been de¬
veloped which is the key in preventing partial overheating and so, in the
near future, it will be possible to continuously pasteurize microwavable dishes
which will have prolonged shelf-life at ambient temperature.
Another development taking place is the application of microwaves to
pipeline heating, enabling a continuous pumped flow rate of particulate
solids to be continuously heated in a microwavable transparent section of
the pipeline. The advantage of this method compared to a conventional tu¬
bular heat exchanger is that it can operate without fouling taking place on
the heating surface.

376
 MICROWAVE COOKING

Microwave processing application has been suggested for the finish drying
of potato chips, dehydration of different pastas, freeze drying, rapid phasing
or roofing of doughnuts, blanching of vegetables, pasteurization and sterili¬
zation of low-acid foods, and especially defrosting of frozen foods.

REFERENCES

Everington, D.W. 1989. The use of microwave heating in meat and fish processing, (in) Pro¬
ceedings of the Second International Food Convention.
Magnus Pyke, 1981. Food Science and Technology, pp. 222-223 edn 4, John Muney, London.
McGraw-Hill. 1979. Modem Plastics Encyclopaedia, vol. 55(10A). McGraw-Hill, New York.
Mudambi, S.R and Rajagopal, M.V. 1980. Fundamentals of Foods and Nutrition. Wiley Eastern
Limited, New Delhi.
Muller, G and Tobin, G. 1980. Nutrition and Food Processing, pp. 248-65. The AVI Publishing
Company, West Port, Connecticut.
Osterdahl, B.C. and Alriksson, E. 1989. Volatile nitrosamines in microwave cooked bacon.
Food Additives Contamination, 1990 7(1): 51-53.
Swanson, B.G. 1984. Economics and Management of Food Processing, pp. 197-250. Smith
Greig, W. (Ed.). AVI Publishing Co., West Port, Connecticut.
Shakunthala, M.N. and Shadaksharaswamy, M. 1995. Food: Facts and Principles. New Age
International Publishers, New Delhi.

LEARNER’S EXERCISE

1. What are the industrial applications of microwave oven?

2. Enumerate the structure and operation of microwave oven.
3. What are the various advantages and disadvantages of microwave cooking?

377
Part VI

Novel food production

and processing
 Mushrooms

M ushroom is a fungal fruiting body which produces and disseminates

spores. Since it is a fungus, it does not possess chlorophyll and hence
cannot produce its own food and depends upon other living or dead plants
to obtain organic matter. Mushrooms are of variable shape and size. Many
have cap and stalk, but there are varieties devoid of stalk. There are a large
number of mushroom species growing wild in nature. While many are edible,
some are mild to deadly poisonous (Vijaya Khader, 1993; Prakash et al,
1986).
Mushroom cultivation is done indoors and hence little land area is re¬
quired. Mushrooms can be grown on substrate or compost based on various
agricultural wastes which in turn are recycled. For establishment of mush¬
room farm one must take into consideration the availability of adequate raw
materials in the area and good local market for fresh mushrooms as they
are perishable and cannot withstand transportation over long distances;
otherwise one should have canning or preservation facilities (Kapoor, 1989).
Mushrooms are popular for their delicacy and flavour rather than food
value. However, it is now a well-established fact that they are excellent sources
of vitamins and minerals (Vijaya Khader, 1988). They contain appreciable
amount of niacin, pantothenic acid and biotin. The vitamins in mushrooms
are well retained during cooking, canning and dehydration.
Their proteins may be considered intermediate between that of animals
and vegetables. Fresh mushrooms contain about 85-95% moisture, 3% pro¬
tein, 4% carbohydrate, 0.3-0.4% fat and 1% minerals and vitamins.
Although many species of mushrooms are edible, a very few have been
artificially cultivated. Most popular ones are white button mushroom
(Agaricus bispoms), paddy straw mushroom (Volvariella spp.), oyster mush¬
room (Pleurotus spp.) and Shiitake (Lentinus edodes). In India, first 3 mush¬
rooms can be artificially cultivated in different parts, depending on the
suitability of season as these varieties need different range of temperature
for growing (Vijaya Khader and Nayana Pandye, 1981a). The white button
mushroom is more acceptable to the consumer and fetches higher price.
For its successful and profitable cultivation, careful attention must be paid
to 4 aspects, i.e. good compost, pure and productive spawn, proper environ¬
mental conditions (temperature, relative humidity and aeration) and good
hygiene of the farm. Details of various stages in the cultivation of white
mushroom are as follows (IIHR, 1986).

381
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

MUSHROOM PROCESSING

Mushroom, an edible fungi, is the most priced commodity among vegeta¬

bles, due to of its nutritive value, characteristic aroma and flavour. In our
country it is mostly sold afresh and a negligible amount is used for process¬
ing. However, where mushrooms can be grown at ambient temperature (like
hilly areas) but cannot be transported quickly to big cities in plains, the only
way of its utilization is its processing. Processed products can then be sent
easily to all consumer centres throughout the country. Increased produc¬
tion at the least cost (i.e. without refrigeration) with a wide market for the
processed mushrooms might induce mushroom-growers particularly those
from remote hilly areas to adopt mushroom processing to their advantage.
It will thus be useful for such an entrepreneur to get acquainted with vari¬
ous aspects of mushroom processing. Therefore, the work carried out at the
Indian Institute of Horticultural Research, Bangalore, and elsewhere is
mentioned here:
Mushroom continues to grow even after removing from the beds. Hence
harvesting for processing has to be done at the proper stage only. It reaches
its peak of perfection for appearance, weight and quality just before the cap
opens to expose gills.
Mushrooms lend themselves to a great variety of culinary treatments.
They may be baked, fried, boiled, creamed, roasted, pickled and stuffed.
They can be processed as canned, dried and frozen mushrooms. Mushroom
ketchup and soup are other important value-added products.

Canning
Mainly buttom mushrooms are used for this purpose. The mushroom
with small button and with 0.5-1.0 cm stem only be selected, and stalk is
cut close to the button. These buttons are blanched for about 5 min. in
steam or boiling water, followed by prompt cooling. Blanching time is deter¬
mined on the basis of catalase test. Blanching removes gases, inactivates
polyphenoloxidase enzyme; reduces bacterial count; improves texture and
gives greater drain weight in the cans. To improve the colour any of these
treatments like use of 0.1-0.2% of citric acid solution for blanching purpose;
immersing in brine containing ascorbic acid and EDTA @ 0.1% and 1000
ppm respectively. Immersing in KMS solution before blanching could also
be given. Blanching causes 25-30% loss in weight; which is unavoidable.
Blanched buttons are filled in plain cans. Filling rate is kept at about 200 g/
0.453 kg jam size can with about 250 ml brine so as to get at least 45%
drain weight. Boiling hot brine containing 1-2% salt and 0.1% citric acid is
poured to fill it up to brim leaving 1.5 cm head-space. Brine with 2% salt,
2% sugar and 0.3% citric acid has also been recommended for this purpose.
Tomato juice has also been tried successfully as a new canning medium at
the IIHR, Bangalore. Exhausting is the next step where filled can is heated

382
 MUSHROOMS

till temperature of 80°C is attained in the centre of the can. This will remove
extra fill as well as air entrapped both in the mushroom tissue and the
liquid media. After exhausting, the cans are hermetically sealed and proc¬
essed in a retort for about 25-30 min. at 0.703 kg/cm2 steam pressure, or
for 15-20 min. at 1.054 kg/cm2 steam pressure. Moreover, processing time
should be increased by 2 min. for every 152.4 m elevation from sea-level.
Prompt cooling is essential after processing and then only cans should be
stored in a cool, dry place.

Dehydration
Mushrooms to be dried are taken at full mature stage and used with full
stalk. Early break (i.e. first flush) gives better product due to low tyrosine
content. It may be dried whole or diced. After washing, they are blanched
for 3-5 min. in live steam or boiling water. Blanched mushrooms may be
given 5 min. dip in sulphite and chlorine solutions of 300 ppm S02 and 400
ppm Cl2 respectively for better colour and lesser bacterial count. Drying can
be done under the sun or in a drier (at 60-70°C temperature). Weight of
dried mushrooms would be about 1/8 to 1 / 12th of their original weight
depending on the mushroom used. Moisture content in dried product should
not be more than 5%. The dried mushrooms are packed in hermetically
sealed airtight tins for quality retention and then stored at a cool dry place.
For reconstitution, sucrose solution with added ascorbic acid is preferred.
However, dried mushrooms are normally powdered and used for prepara¬
tion of soup mixes. Most of the commercial dried mushrooms of the world
are derived from Boletus species (a thick, fleshy mushroom) growing wild in
pine forests in Europe and South West America (Vijaya Khader, 1993).
Freeze drying: Agaricus bisporus to be used for this purpose, should be
processed within 3 hours of harvest. For inhibiting the activity of
polyphenoloxidase enzyme, it may be given a dip for 30 min. either in 0.5%
NaHS03 solution or 2% NaCl solution. Blanching is then done for 2 min. in
boiling water, followed by prompt cooling. Then it is diced or sliced into 5
mm thick pieces and frozen at -34°C by dipping in Freon-12 for about a
minute; as quick freezing gives a better quality product. Frozen mushrooms
are dried within 6-8 hr at low temperature under partial vacuum to a 3%
moisture level. For better retention of quality, freeze-dried mushrooms are
packed in aluminium foil containing pouches under N2 atmosphere and
stored at lower temperature. A 12-kg fresh mushroom gives 1 kg freeze-
dried product which can yield 8 kg reconstituted material.
Freezing: Agaricus bisporus is used at the same stage as in the case of
canning. The buttons are pre-cooled to 2-4°C; washed with water contain¬
ing 50 ppm Cl followed by 2-3 min. blanch in water containing 0.1% citric
acid. They can then be frozen as such or after packing in pouches. Freon-12
is used for quick freezing. Frozen mushrooms are to be stored only at-20°C.
Entire chain used for its marking (i.e. from freezing till it is consumed) has

383
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

to be as refrigerated one maintaining a temperature of -20°C throughout.

Today quick frozen mushrooms are in better demand in the world market
because these could be stored even up to 1 year in storage chamber of the
deep-freeze without any loss of flavour.

Steeping preservation
After washing, mushrooms are to be blanched for 5 min. in water con¬
taining 0.1% citric acid followed by washing in cool plain water. Then they
are put in 15% salt solution containing 0.05% critic acid and 100 ppm S02.
By this method mushroom could be preserved only for a short period (about
2 months).
Mushroom pickles, mushroom ketchup, mushroom sauce, mushroom
flakes, mushroom instant soup powder and mushroom masala powder are
some of the processed mushroom products (Vijaya Khader and Nayana
Pandye, 1981b).

REFERENCES

IIHR, 1986. Mushroom cultivation. Extension Bulletin 8: 5-36. Indian Institute of Horticultural
Research, Bangalore.
Kapoor, J.N. 1989. Mushroom Cultivation, pp. 5-11. Indian Council of Agricultural Research,
New Delhi.
Prakash, T.N., Tejaswini and Ramana, R. 1986. Mushroom, a promising crop for future. SBM
Farm News 9: 5-7.
Vijaya Khader. 1988. Studies on oyster mushrooms (Pleurotus). The Andhra Agricultural Journal
' 35(3 and 4): 212-214.
Vijaya Khader. 1993. Mushrooms for livelihood. Kalyani Publishers, 1/1, Rajindernagar,
Ludhiana.
Vijaya Khader and Nayana Pandye, B. 1981a. Nutritional studies on paddy straw mushroom.
Indian Journal of Mushrooms 7(1 and 2): 18-25.
Vijaya Khader and Nayana Pandye, B. 1981b. Acceptability studies on weaning foods and
pickle prepared out of paddy straw mushrooms and the keeping quality of the same.
Indian Journal of Mushrooms 7(1 and 2): 31-36.

LEARNER’S EXERCISE

1. What is mushroom and name the most common edible mushrooms?

2. Discuss various processing techniques of mushrooms.
3. Explain about dehydration of mushrooms.

384
 Blue green algae
{SpiruUna) 27.
B lue green algae, Spirulina, is being used as nutrient dense food material
in natural and health food and for some therapeutic uses. It also has
some potent probiotic compounds that enhance health. Interest in food ap¬
plication of micro-algae has its origin on 2 counts. Firstly, in certain countries
a small section of the population have been eating naturally grown algae
harvested from lakes etc. without ill-effects for centuries (Becker, 1986).
Secondly, the focus on protein-calorie malnutrition in the third world coun¬
tries was drawn by the FAO in sixties which led to the identification of
newer protein sources particularly the single cell protein which includes
algae (FAO, 1963). Micro-algae by virtue of the high protein content (45-
70%) and good photosynthetic efficiency have attracted worldwide attention
(Richmond, 1986, 1988).
Initially it was the green algae Chlorella and Scenedesmus which re¬
ceived attention and in eighties, a cyanobacterium, Spirulina had overtaken
the lucrative Chlorella production dominated earlier by Japanese (Klausner,
1986). Presently spirulina commands a premium price in health food mar¬
ket. Internationally, spirulina application has been increasing due to the
technology being easily adaptable and algae being nutrient dense.
In a meeting on 13 and 14 December 1973, PAG recalled that the term
single-cell protein had been selected in 1966 as the title for the first interna¬
tional conference organized on this subject. It was considered a new and
sufficiently neutral term, which would avoid the connotations of microbial
protein, bacterial protein and, above all, petroleum protein.
Protein derived from bacteria, yeasts, moulds and algae can, thus, be
called single-cell proteins though the name is not an accurate description of
these materials, since some of them are not monocellular at all. Apart from
proteins, these organisms also contain carbohydrates, lipids, nucleic acids,
vitamins and minerals. Thus, in addition to proteins, they also ensure an
intake of energy and other nutrients.
Worldwide, more than 1,200 tonnes of Spirulina is being produced with
the major centres in Japan, United States, Vietnam, Taiwan and Thailand.
It is presently marketed in the west, Japan and West Asian countries in
health and natural food markets. In India the Central Food Technological
Research Institute, Mysore, has carried out extensive work over the last 30
years on technology, composition, nutritional quality, safety evaluation, prod¬
uct formulations and limited clinical trials. Feeding Spirulina to humans

385
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

and rats as major dietary emuliorant, or a prophylactant against the pesti¬

cide-associated health risks is a new concept, which is being explored at the
CFTRI, Mysore (Venkataraman etal, 1994).

TECHNOLOGY

The alga consists of spiral cylindrical filaments with a length of about 300-500
pm with width of spirals 6-8 mm (Fig. 63).
Cultivation of Spirulina involves 3 well-defined steps—cultivation, har¬
vesting and drying. The alga is cultivated in open outdoor tanks with well-
defined nutrient medium (Zurrouk or CFTRI medium) and supply of carbon
dioxide and agitation by motor-driven paddles. Harvesting of the algal biomass
is done periodically from the cultures when the concentration reaches 0.6
OD which corresponds to 60 mg dry algae/100 ml culture (Venkataraman,
1989). Harvesting of biomass is done on a conveyer-type harvester using
fine nylon mesh. The wet algal biomass is homogenized and dried in a spray
drier to obtain food-grade material. The steps involved in the production of
this alga is shwon in Fig. 64.
Constituents
Spirulina is the most nutrient-dense food currently known with a pro-
Table 37. Composition of spray-dried Spirulina (constituents /100 g)

Constituents Value

Major constituents
Protein 65-71%
Fat 0.6-07%
Curde fibre 9.3%
Carbohydrates 16.0%
Calories 346
Vitamins
Beta-carotene 320,000 IU
Biotin 0.22 mg
Cyanocobalamin (B12) 65.7mcg
Folic acid 17.6 meg
Other B-complex vitamins 9.2 meg
Tocopherol (E) 0.73 IU
Minerals
Calcium 658 mg
Phosphorus 977 mg
Iron 47.7 mg
Sodium 796 mg
Potassium 1,140 mg
Essential amino acids
Lysine 2.99%
Cystine 0.47%
Methionine 1.38%
Phenylalanine 2.87%
Theonine 3.04%

386
 GREEN ALGAE (SPIRULINA)

Fig. 63. Microscopic view of Spirulina

Fig. 64. Spirulina production and its applications

tein content of more than 60% with high availability of essential amino
acids (Venkataraman, 1993). It is an excellent source of vitamins including
beta-carotene (provitamin A), Bv B2, B6, B12, C, E and biotin. The pigments
include chlorophylls, carotenoids, xanthophylls and phycocyanin. The chemi¬
cal composition is shown in Table 37. The toxicological evaluation of Spirulina
which states, Spirulina when administered at 10, 20 and 30% levels in diet

387
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

does not produce any sub-acute or chronic toxicity, changes in reproduction

and lactation or mutagenicity and teratogenecity. Microbiological examination
of the culture and the products generally contain insignificant contamination
(Mahadevaswamy and Venkataraman, 1986).
The other valuable constituent is gamma-linolenic acid which is a poly¬
unsaturated fatty acid (PUFA). This along with superoxide dismutase (SOD)
acts as anti-oxidant and hence useful in chemoprevention. There is no starch
but the carbohydrates are in the form of water-soluble polysaccharides. The
alga may also have potent probiotic compounds that enhance health. Com¬
parison of this alga with milk and egg is given in Table 38 (Venkataraman
and Becker, 1984 and 1986).

Table 38. Composition of Spirulina to milk and egg

Composition 10 g Spirulina 200 ml milk 1 egg

Protein 6.6 g 6.6 g 6.6 g

Vitamin A 14,000 iu 248 iu 1,050 iu
Nicotinic acid 1.18 mg 0.20 mg 0.04 mg
Riboflavin 0.40 mg 0.38 mg 0.19 mg
Thiamine 0.55 mg 0.01 mg 0.095 mg
Vitamin B12 30.0 pg 0.28 pg 2.3 ng
Iron 5.8 mg 0.40 mg 1.6 mg

Nutritional quality and safety

The protein efficiency ratio (PER) value of Spirulina has been reported to
be higher than vegetables, cereals and soy-proteins. The values of the di¬
gestibility coefficient, biological values etc. are given in Table 39. These values
are only marginally lower than casein. Supplementation of Spirulina to cereals
like rice and wheat on isoproteinic levels improves the protein quality (Bamji,
1997). The bioavailability of vitamins has also been reported to be good.
Spirulina has been considered as a natural source of vitamins and can be
used to meet the RDA of vitamins, particularly for economically weaker sec¬
tions in India. Evaluation of Spirulina supplementation is being carried out
with young pre-school and school children at the Pudukottai Distt. of Tamil
Nadu by Murugappa Chettiar Research Centre (MCRC), Chennai, under
Department of Biotechnology Programme. The preliminary data collected so
far have shown very encouraging results, particularly in correcting the vita¬
min A deficiency (Umesh and Seshagini, 1986).

Table 39. Nutritional value of Spirulina

Protein source Protein level (%) PER DC BV NPU

Casein 10 2.50 95.3 94.4 89.9

Spirulina plantensis spray dried 10 1.89 91.9 79.5 75.0

PER, Protein efficiency ratio; DC, digestibility coefficient; BV, biological value; NPU, net protein utilization

388
 GREEN ALGAE (SPIRULINA)

Extensive animal experiments and limited clinical trials carried out in

India and elsewhere have shown the harmlessness of even sundried Spirulina.
There is a UNIDO document (Chamorro, 1982) on the toxicological evaluation
of Spirulina which states, Spirulina when administered at 10, 20 and 30%
levels in diet does not produce any suh-acute or chronic toxicity, changes in
reproduction and lactation or mutagenicity and teratogenecity. Microbio¬
logical examination of the culture and the products generally contain insig¬
nificant contamination (Mahadevaswamy and Venkataraman, 1986).

Therapeutic applications
The p-carotene content of Spirulina is 18 times more than carrot, which
is the normally known popular source. The natural p-carotene of Spirulina
is different from the synthetic p-carotene, as it contains high percentage of
9-cis-isomer than over 47% of all trans in synthetic form. The p-carotene as
a dietary supplement has been shown to inhibit the development of 7,12
dimethyl benzanthrazene (DMBA) induced salivary gland carcinomas in rats.
The p-carotene has also been shown to inhibit UV induced skin cancer in
hairless mice. It has been sugested that p-carotene can reduce human
cancer rates (Norman and Basu, 1988) based on epidemiologic studies
showing an inverse association of dietary intake of p-carotene and cancer
incidence.
The antioxidant properties of Spirulina were seen in in vitro studies using
human erythrocyte ghost. Both alcohol and decolourized aqueous extract of
Spirulina effectively inhibit lipid peroxidation induced by ferrous sulphate
and ascorbic acid in erythrocyte membrane. The result indicates that
Spirulina extracts could be effective against free radical induced lipid
peroxidation which may lead to cellular transformation (Manoj etal, 1991).
Another constituent in Spirulina which is of commercial importance is
its high content of polyunsaturated fatty acids. The most important essential
fatty acids are gamma-linolenic acid (GLA), dihomo gamma-linolenic acid
(DGLA) and polyunsaturated fatty acids (PUFA) such as omega-3-fattyacids
eicosa pentanoic and decosa pentanoic acid (Venkataraman, 1989).
The hypoglycemic effect of Spirulina in non-insulin-dependent diabetes
mellitus (NIDDM) patients has been shown in limited clinical studies carried
out at Coimbatore. Venkataraman (1989) reported significant reduction in
the fasting and post-prandial blood and urine sugar levels with the intake of
about 2 g Spirulina in the form of capsules. This has also been established
in animal experiments using albino rats with alloxan induced diabetes. The
reason for the reduction in the sugar levels may be attributed to the
prostaglandin stimulation. More critical studies need to be carried out on
this aspect, not merely to establish the levels of Spirulina tablets, but also to
understand the mechanism.
Cholesterol-lowering property of Spirulina has been very well documented
both in animal experiments and in clinical trials. The stimulant effect of

389
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Spirulina on lactation in rats have been shown when fed to pregnant Wistar
rats from 14th day of postnatal period (Venkataraman, 1989). A significant
increase in the litter weight and milk content has been reported when
Spirulina was supplemented at 500 ppm level. In Vietnam, Spirulina is com¬
mercially sold as lactogil to increase the milk production in nursing mothers.
Mahadevaswamy and Venkataraman (1986) reported healing of epidermal
blisters and wounds in the skin of male rats treated with ointment based on
Spirulina (15%). Spirulina as active ingredient produced accelerated
cicatrization of wounds leading to complete recovery at a shorter time than
with salicylic acid-based commercial ointment.
The anecdotal claims for probiotic action resulting from dietary use of
microalgae are many, and not supported by well-planned animal studies or
clinical trials. Important constituents like betacarotene, tocopherols, linolenic
acid and ascorbic acid have certain type of physiological activity at low in¬
takes and give different effect at high intakes. There are yet unidentified
constituents in Spirulina which need more detailed study.

Cosmetics
There is an increasing interest to develop skin ointments and range of
beauty products by incorporating Spirulina in reducing lotions, antiwrinkle
creams, pimple lotion and face masks. This is not merely due to high pro¬
tein and vitamin contained in the alga but also due to the presence of sig¬
nificant amounts of superoxide dismutase (SOD) which has been correlated
to the ageing process (Venkataraman, 1991). The pigment phycocyanin of
Spirulina has been marked in Japan as Linablue which is a safe biolipstick.
Recent reports indicate that certain compounds required to serum-free cul¬
tures of mammalian cell lines and which currently originate from animals,
can be extracted from Spirulina. The phycobiliproteins are now used as fluo¬
rescence tag to couple antibodies for immunodiagnostics and these are called
‘phycoflour probe’. This has a high potential in medical field (Venkataraman,
1989).

Quality standards
The quality standards for food-grade Spirulina has now been released
as a document by the Bueau of Indian Standards (IS: 12895:1990). This will
assure the quality standards or commercially produced Spirulina to be used
in various formulations and also for exports.

REFERENCES

Anusuya Devi, M. and Venkataraman, L.V. 1983. Supplementary value of the proteins of the
blue green algae Spirulinaplatensis to rice and wheat proteins. Nutritional Report Interna¬
tional 2&: 1,029.
Becker, E.W. 1986. Nutritional properties of micro-algae potentials and constraints, (in) Hand¬
book of Micro-algal Mass Culture, pp. 381-86. CRC Press, Inc., Florida.

390
 GREEN ALGAE (SPIRULINA)

Bamji, M.S. 1991. Blue green alga spirulina. A source of vitamin A in children’s diet. Nutrition
News 12 (6): 1-3.
Chamorro, G. 1982. Etude toxicological del; algae Spirulina pilote prouuctive de proteines
(Spirulina de sose Texcoce, S.A.) UF/MEX/78/048, UNIDO/10,387. 1-177.
Farrar, W.V. 1966. Tecuitlati’. A glimpse of Aztec food technology. Nature 211: 341.
FAO. 1963. ‘Third World Food Survey—Basic Study. Food and Agriculture Organization, Rome.
Klausner, A. 1986. Alga culture: Food for thought. Biotechnology 4: 947.
Mahadevaswamy, M. and Venkataraman, L.V. 1986. Bacterial contaminants in blue green
alga spinulina produced for biomass protein. Arch. Hydrobiol (Algological studies) 110(4):
625.
Manoj, G., Venkataraman, L.V. and Srinivas, Leela. 1991. Antioxidant properties of Spirulina
tplatensis. (in) Proceedings Spirulina, ETTA National Symposium, held at Madras.
Norman, J. Temple and Basu, T.K. 1988. Does Beta carotene prevent cancer? Critical Ap¬
praisal. Nutrition Research 8: 685-701.
Richmond, A. 1986. Handbook of Micro-algal Mass Culture, pp. 381-86. CRC Press Inc., Florida.
Richmond, A. 1988. Spirulina. (in) Microalgal Biotechnology, pp.85. Borowitzka, M.A. and
Borowitzka, L.J. (Eds). Cambridge University Press, Cambridge, New York.
Venkataraman, L.V. 1989. Spirulina: State of art and emerging prospects. Phykos2S(\ and 2):
231.
Venkataraman, L.V. 1991. What next on Spirulina? (In) Proceedings Spirulina, ETTA National
Symposium, held at Madras.
Venkataraman, L.V. 1993. Spirulina in India. (In) Proceedings of the National Seminar on
‘Cyanobacteria Research-Indian Scene’, pp. 92-116. Subramaniam, G. (Ed.). National
Facility for Marine Cyanobacteria, Tiruchirapalli, India.
Venkataraman, L.V. and Becker, E.W. 1984. Production and utilization of blue green algae
Spirulina in India. Biomass 4: 106-25.
Venkataraman, L.V. and Becker, E.W. 1986. Biotechnology and Utilization of Algae. The In¬
dian Experience. Department of Science and Technology, New Delhi.
Venkataraman, L.V., Suvamalatha, G., Krishna Kumari, M.K. and Pius Joseph. 1994. Spirulina
platensis as retinol supplement for protection against henachlorocyclohexane toxicity in
rats. Journal of Food Science and Technology 31(5): 430-432.

LEARNER’S EXERCISE

1. Give spray dried spirulina composition.

2. Explain nutritional quality and safety of algae.
3. What are the various therapeutic applications of spirulina?

391
 Leaf protein
concentrates (LPC)

P lant proteins are synthesized in the leaf and partly translocated to seed
or tubers. In suitable climates, forage crops maintained as photosyn-
thetically active structure throughout the year. Because of the elimination
of translocation losses and the ripening period, forage can yield more pro¬
tein and dry matter than any other type of crop, but this advantage is usu¬
ally lost if the forage is fed to ruminants, as they convert only 5-25% of their
feed into products that people eat (Pirir, 1979). It is easy to extract 40-60%
of the protein from many types of leaves, to separate palatable protein from
the extract, and this removes strongly flavoured (or even toxic) leaf compo¬
nents from the curd. The annual yield of diy protein can be 2 tonnes/ha in
Britain and 3 tonnes/ha in India.
Soft, lush leaves are easier to extract than leaves that are fibrous or dry,
even when pulped with added alkali, leaves do not extract well, and glute-
nous or slimy extracts are difficult to handle.
Protein-containing juice is liberated from leaves by rubbing and bruis¬
ing, fine subdivision is not essential, it may be detrimental. Leaf protein can
be coagulated by acidification or heating the extract. Heating is preferable
because it partially sterilizes the curd and gives it a texture that makes
filtration easy. Acidification ensures the removal of alkaloids, but it converts
chlrophyll to pheophytin and increases the rate of oxidative loss of p-caro-
tene. Furthermore, the dull green is less attractive than the bright colour of
neutral leaf protein.
Carefully made dry leaf protein contains 6(3-65% true protein and
0.1-0.2% p-carotene. Feeding experiments with chicks, mice, pigs and rats
showed that leaf protein is safe and nutritionally useful. Experiments on
human subjects (children) also showed good nitrogen retention, improved
growth rate and improved appetite and mental alertness.
The main merit of leaf protein compared with most other novel foods is
that it could be made in villages, where in the less developed countries, the
need for improved nutrition is the greatest (Pirie, 1978).
Process of isolation of leafy protein is given in Fig.65 (Muller and Tobin,
1980).
Leaf protein isolates contain 10-20% protein on the dry basis.
The fact that the isolation of leafy protein for food has not so far been
used by a large industry indicates that there are problems. Basically, for the
process to be economical, sufficient amount of soluble fresh green foliage

392
 LEAF PROTEIN CONCENTRATES (LPC)

Filtration » Water solubles

Washing

Canning Drying

Wet cake Dried protein concentrate

Fig. 65. Isolation of leaf protein

must be available at the processing plant to safeguard a continuous run.

Processes for producing a colourless and tasteless protein concentrate or
isolate have to be developed.
Research has been carried out on the extraction of protein from the
leaves of several food crops, viz. pea, beans and potato by pulping the leaves
and expressing the juice. The juice is heated to coagulate protein which has
a cheese-like texture and a dark-green colour. One of the problems with leaf
protein is that it is generally unacceptable to the consumer because of dark
colour. It has some degree of acceptance in certain parts of the world. Further
research is needed to develop this process to give a more attractive food to
overcome prejudice against the green colour or to remove the colour alto¬
gether.

REFERENCES

Muller, H.G. and Tobin, G. 1980. Nutrition and Food Processing. AVI Publishing Co., Inc. West
Port, Connecticut, London.
Pirie, N.W. 1979. Protein for leaf protein on human food. Journal of American Oil Chemists’
Society 56: 472.
Pirie, N.W. 1978. Leaf Protein and other Aspects of Fodder Fractionation. Cambridge University
Press, London.

393
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

LERNER’S EXERCISE

1. Explain in detail about the isolation of leaf protein concentrates.

2. Give various constituents of leaf protein concentrates.

394
 Protein from
petroleum yeast

SINGLE CELL PROTEINS

M icro-organisms have a high protein content and contain useful quan¬

tities of vitamins. Their rate of growth is very rapid, and the rate of
protein synthesis in micro-organisms has been compared favourably with
that of animals. A 500 kg bullock produces an extra 500 g protein/day,
whereas 500 kg yeast grown in suitable conditions can produce 50 tonnes
protein in 1 day. It can be seen that micro-organisms are potentially a very
valuable source of protein, especially if they can be produced economically
by the use of a cheap food. Work has been carried out on bacteria which
utilizes methanol obtained by the oxidation of natural gas (Gaman and
Sherrington, 1989).
Algae, which do not require organic material for growth, theoretically
have an even greater potential as a protein food. Extensive research has
been carried out on the production of protein from algae, particularly from
the Chlorella species.
Single cell proteins like Scenedesmug obliques, Chlorella pyrenodosa, a
type of algae, and many more yeast cells help in producing more protein
from the industrial waste like spent grains, rot vegetables, fruits, bagasses
of sugarcane, molasses, washed water, unwanted meat and poultry waste,
from fish and shrimp wastes. These single cell proteins increase the protein
by 50-60% and enhance the sugars for alcohol conversion, the minerals
and vitamins, bioavailability also increases. Now the food-processing indus¬
tries are using these single cell organisms in the field of biotechnology.
The commercial production of yeasts by fermentation on certain hydro¬
carbons is now an accomplished fact and is taking place in the United Kingdon
and France. These yeasts are included in the class of products widely, some¬
what imprecisely, referred to as single-cell proteins (SCP). In contrast to
some other materials in this category, these yeasts are intended to be used
indirectly for human nutrition; they are currently being produced for inclu¬
sion in animal feed stuffs.
Though indirect, their influence on human nutrition may be two-fold.
Firstly, they could facilitate the starting up or extension of animal indus¬
tries in areas where at present these are rudimentary or non-existent. Sec¬
ondly, they could remove some of the pressure on more conventional animal
feed materials, such as oilseeds and fish products, thus releasing more of

395
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

these products for direct human use (Shecklody, 1975). These have been
described in detail by Bennett et al (1969, 1971). According to them, 2
alternative feedstocks may be used. One is a mixture of pure linear alkanes
(n-paraffins) and the other is a middle distillate of oil boiling in the 280-400°C
range.
The purity of the n-alkanes must be such as to meet the specification
for food grade mineral oil as defined by FDA specification 121.1146 or that
recognized by the FAO/WHO. In addition, the n-paraffins should contain
less than 1 pg/kg of each of the following polycyclic aromatic compounds; 3,
4-benzpyrene, dibenz[a,h)anthracene, benz [g, h, i] perylene and 3-methyl-
cholanthrene. Such paraffins are usually produced by a molecular sieve
process followed by one of the several possible finishing treatments.
This is a new departure in fermentation technology since, hitherto, the
production of yeast on the more conventional carbohydrate substrates has
been a batch process.
The degree of purity of the n-paraffins is so high that, after fermenta¬
tion, the yeast needs only to be concentrated by centrifugation, washed and
dried. There is a low level—less than 0.5%—of residual hydrocarbon associ¬
ated with the yeast but this has been shown to present no toxic hazard
whatsoever, nor it is expected to prove an embarrassment in view of the
purity of the feedstock.
If middle distillate is used as the feedstock, only a portion—represent¬
ing the n-paraffin content of the mixed hydrocarbons—is consumed by the
micro-organisms, for growth. The remaining hydrocarbon must be removed
by centrifugation, washing, and finally by solvent extraction, this last step
being unnecessary, as already seen, in the n-paraffin process.

Product
The result, in either case, is a cream-coloured powder with no smell
and, virtually, no taste. A typical analysis of the commercially produced
material would be as shown in Table 40 (Sheklody, 1975).

Table 40. Characteristics of hydrocarbon-grown yeasts

% by weight n-paraffin Middle distillate

yeast yeast

Moisture 4-7% 4-7%

Dry-matter basis
Crude protein (N x 6.25) 60 68
Total lipids after acid 10 1.5-2.5
hydrolysis
Phosphorus 1.6 1.5
Calcium 0.01 0.3
Pepsin digestibility (%) >80 >80

396
 PROTEIN FROM PETROLEUM YEAST

It can be seen that the effect of the solvent extraction to which the yeast
from middle distillate was subjected has been to remove some of the natural
lipids from the yeast and consequently to increase the content of protein.

Safety of hydrocarbon-grown yeasts

Products which are, in themselves, new or are the result of new tech¬
nology cannot be assumed to be safe; their freedom from toxicity must be
demonstrated by appropriate tests before they are put into general use.
These yeasts do not present any threat to existing agricultural products;
they are complementary to them and add to the pool of raw materials from
which the quantity and quality of livestock may be improved, for the ulti¬
mate benefit of all.

Microbial protein
Perhaps the earliest fermentation processes are the manufacture of al¬
cohol (ethanol) and vinegar (acetic acid) by micro-organisms. Today, there
are many such processes. Antibiotics, enzymes, amino acids and vitamins,
citric and lactic acids as well as various carbohydrates are produced by
fermentation methods on an industrial scale. One of the most important
features of such fermentations is a high yield of the end-product, and suitable
strains of micro-organisms have been developed to that end. With these
fermentations the organism itself is often discarded, but in the manufacture
of microbial protein, the organism itself is the end-product and a maximum
growth rate is required on any given substrate.
Such substrates include hydrocarbons, alcohols, agricultural byproducts
such as whey and molasses, as well as sewage and industrial waste. Some
examples of micro-organisms and their substrates (Benett et al, 1969), are
given in Table 41.
Table 41. Micro-organisms used in the manufacture of microbial protein and their substrates
^
Organism Substrate

Bacteria
Cellulomonas Cellulose wastes, such as wood, paper, cotton, textiles
Pseudomonas Methanol
Protaminobacter Methanol
Hyphomicrobium Methanol
Methylococcus Methane
Methanomonas Methane

Yeast
Candida spp n-alkanes, crude gas oil

Fungi
Aspergillus mger Carob bean waste
Fusarium graminarium Several carbohydrae substrates

Alga
Spirulina maxima Carbondioxide

397
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Algae, being autotrophs, require only water, mineral salts and, as their
only carbon source, carbondioxide. The limiting growth factor is sunlight.
Therefore, in the open, algae grow best in the tropics. Commercially, a bal¬
ance must be drawn between maximum stocking and maximum exposure
to sunlight. The other micro-organisms are heterotrophs and require or¬
ganic carbon as a food source. They are usually grown in fermenters where
the growth medium and air are supplied. The micro-organisms are har¬
vested by filtration or centrifugation. They are finally dried and sold as a
powder or pelleted as a cattle food (Benett etal, 1971).
During fermentation, control of temperature is important. All fermenta¬
tion reactions are exothermic and cooling is required. The oxygen content of
the substrate molecules is also important. If it is high, as with carbohy¬
drates or cellulose wastes, little gaseous oxygen is required. And if it is low,
as with methane, methanol or gas oil, considerable more gaseous oxygen
must be supplied to the system.
Industrially, good progress has been made with the fermentation of
methanol. An unusual feature of this process is the pressure cycle fermenter.
This allows the oxygen concentration to be increased more effectively than
with traditional fermenters fitted with power-driven paddles. This system is
shown in Fig. 66. There is a continuous feed to the fermenter of the sterile

Methanol Nutrients Air Ammonia

-> Sterilizing filter*-

Sterilizing filter

Cooler 4

^Fermentation-
vessel-» Exhaust gas

Centrifugation

Drying

Pseudomonas

Fig.66. Manufacture of Pseudomonas from methanol

398
 PROTEIN FROM PETROLEUM YEAST

nutrient solution, methanol and a mixture of air and ammonia. After 3

days, an optimum concentration of micro-organism is reached, and then a
small amount is continually removed from the system. The micro-organ¬
isms are separated by centrifugation. The solution is recycled and the micro¬
organisms are spray-dried.
Nutritional properties of microbial protein
The protein recovery in microbial fermentations is generally high, i.e.
50-75% on the dry basis. Since the protein is high in lysine, it is useful
when combined with a cereal diet which is lysine-deficient. As with many
plant proteins, it is deficient in methionine; but B vitamins and iron levels
are high. There are, however, possible disadvantages related to microbial
protein. Traces of substrate may be left out containing carcinogenic polycyclic
aromatic compounds. However, often the levels of these are higher in some
conventional foods than in, say, yeast grown on an alkane substrate. For
instance, the content of 3, 4-benzypyrene of such yeast is (per kg of
dry matter) between 5 and 13 mg, whereas in lettuce and spinach it is 12 m,
in endive 50 mg and in some algae as high as 60 mg.
Nevertheless, in using microbial protein, caution must be taken be¬
cause it is unlikely that lettuce will form a major part of the daily diet, but
microbial protein could well do so. The relatively high levels of nucleic acids
have also given rise to concern. Clearly, nucleic acids are of genetic impor¬
tance but, so far, there is no concrete evidence of any harmful effects of
nucleic acids at the levels to be expected.

Table 42. Analytical and nutritional data of some micro-organisms and conventional foods
(per 100 g dry basis)

Micro-organisms Protein Fat Carbohydrate BV NPU PER

Spirulina 60 3 20 0.73 0.61 -

Saccharomyces 50 2 30 0.67 0.56 2.2

Candida 70 8 25 0.73 0.62 1.0
Fusarium 60 1 40 - 0.60 2.7
Pseudomonas 80 14 5 0.79 0.76 -

BV, Biological value; NPU, Net protein utilization; PER, Protein efficiency ratio

Analytical and nutritional data for some micro-organisms on a dry ba¬

sis are given in Table 41. While the protein content is remarkably high, fat
and carbohydrate contents tends to be low but variable. On the same dry
basis, wheat, potato, fish and meat would have protein contents of 15, 10,
85 and 50% whereas their carbohydrate contents would be 80, 70, 0 and
0% respectively. The nutritive value of microbial protein lies on the whole
halfway between that of cereals and of meat.

399
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

REFERENCES

Benett, I.C., Yeo, A.A. and Gosling, J.A. 1971. Chemical Engineering, 27 Dec. 1971, 45-7.
Benett, I.C., Hondermarck, J.C. and Todd, J.R. 1969. Hydrocarbon Processing, Chemical En¬
gineering, 20-23 March.
Gaman, P.M. and Sherrington, K.B. 1989. The Science of Food—An Introduction to Food Science,
Nutrition and Microbiology, pp. 48-50. Pergoun Press, Oxford, New York.
Shacklody, C.A. 1975. Food Protein Sources in International Biological Programme, pp. 40-50.
Pirie, N.W. (Ed.) Cambridge University Press.

LEARNER’S EXERCISE

1. What is Chlorella?
2. Explain the safety of hydrocarbon-grown yeast.
3. What are the various nutritional properties of microbial proteins?
4. Explain through schematic diagram the manufacture of pseudomonos from methanol.

400
 By-products
of oilseeds

N uts and oilseeds are in general rich sources of proteins (with the excep¬
tion of coconut) and of fat. Edible oilseed meals obtained from oilseeds
are rich in proteins and have been used for the preparation of infant foods,
and protein foods for feeding infants and preschool children in developing
countries.

EDIBLE OILSEED MEAL

The steps involved in the preparation of oil and edible meal from nuts and
oilseeds are as follows: (i) cleaning and dehusking, (it) removing oil from the
kernel (free of husk) by one of the following methods: (a) mechanical press¬
ing (hydraulic pressing), (b) screw pressing, (c) prepress solvent extraction
and (d) direct solvent exraction.
The method of preparation of edible meals from soybean, cotton seed,
peanut (groundnut) and sesame is described in this chapter. Protein Advi¬
sory Group specifications for-these products are given in Table 43
(Swaminathan, 1987).

Soybean meal
The processing of soybean involves the following steps: (z) cleaning,
(iz) dehulling of the seed, (in) steaming of dehulled split seeds and drying,
(iv) screw pressing or solvent extraction for removal of oil, and (z/) powdering.
Cleaning and dehulling: Soybean is cleaned of all impurities. The cleaned
seed is passed through a huller to remove hulls. The dehulled seed is-split.
Steaming and drying: The dehulled seed is soaked in water for 1 hr and
water is drained off. The wet material is heated in steam at 6.35 kg pressure
for 30 min. to inactivate trypsin and growth inhibitors, haemagglutinins,
etc. The steamed seed is dried under the sun or in a tunnel drier.
Screw pressing or solvent extraction: The oil from heat-processed seed is
removed by pressing in a screw press or by solvent extraction.
Powdering: The cake is powdered in a hammer mill to pass through 50
mesh sieve (Nerosinga Rao, 1989).

Groundnut (peanut) meal

The processing of peanut for edible meal consists of the following steps:
(z) cleaning of good-quality kernels from impurities, (z'z) light roasting and

401
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Table 43. Specifications for edible groundnut, cotton seed and soya flours as suggested by the
Protein Advisory Group

Composition Groundnut Cotton¬ Soya flour Soya flour Sesame

flour seed flour (defatted) (full fat) (defatted)

Moisture (%) 7.0-11 10.0 12.0 10 9

(range or max.)
Crude fat (%) (max.) 8.0 6.0 0.5-3.0 18-22 1.5
Protein (N x 6.25) 48.0 50.0 45.0-52.0 38-44 50.0
Crude fibre (%) (max.) 3.5 - 3.5 3.5 6.0
Ash (%) (max.) 4.5 - 6.0 6.0 6.2
FFA (%) of oil (max.) 1.0 1.8 - - 4.0
Available lysine 2.5 3.6 5.0 5.0 2.4
(g/16 g N) (min.)
Acid insoluble ash 0.1 0.1 0.1 0.1 0.1
(%) (max.)
Aflatoxin (pg/kg) (max.) 30.0 30.0 30.0 30.0 30.0
Total bacterial count/g 20,000 20,000 20,000 20,000 20,000
Salmonella Nil Nil Nil Nil Nil
E. coli Nil Nil Nil Nil Nil
Other pathogens Nil Nil Nil Nil Nil
Total gossypol (%) - 1.2 - - -

(max.)
Free gossypol (%) (max.) - 0.06 - - -

Oxalic acid (%) - - - - 0.5

by weight (max)

Max., Maximum; Min., minimum

decuticling, (zzz) removal of germ and fungus-affected kernels and (iv) screw
pressing or solvent extraction.
Cleaning: Good quality of groundnut kernels are cleaned of all impurities.
Roasting and decuticling: The kernel is roasted lightly for 5-10 min. The
red cuticle is removed by rubbing. The germs are separated and the fungus-
affected kernels are removed by hand picking.
Screw pressing: The cleaned decuticled kernels are pressed in a screw
press (expeller) for removing the oil. The resulting white cake containing
about 8% oil is powdered in a hammer mill. The cake can be extracted with
food-grade hexane to obtain fat-free flour.

Cotton-seed meal
The processing of cotton-seed consists of following steps: (z) cleaning,
delinting and dehulling; (zz) steaming of kernels, and (zzz) screw pressing or
solvent extraction.
Cleaning, delinting and dehulling: Good quality cotton-seed is cleaned of
impurities. It is delinted and dehulled.
Steaming of kernels: The kernels are steamed for 15 min. to fix free gossypol
in the bound form.
Screw pressing or solvent extraction: The steamed kernel is pressed in a

402
 BY-PRODUCTS OF OILSEEDS

screw press. The resulting cake containing about 8-10% oil is powdered in
a hammer mill. If a fat-free flour is required, the cake can be extracted with
food-grade hexane.

Sesame meal
The processing of sesame for production of edible flour consists of the
following steps: (z) cleaning and dehulling of sesame seeds and (zz) screw
pressing or solvent extraction.
Cleaning and dehulling: Sesame seeds are cleaned of impurities. The
dehulling is carried out by soaking seed in water or in dilute alkali and
removing skin by rubbing. The dehulled seeds are dried in a tunnel drier.
Screw pressing or solvent extraction: The dehulled seeds are pressed in a
screw press. The resulting white sesame cake containing about 10% oil is
powdered in a hammer mill. If a fat-free flour is desired, the cake is ex¬
tracted with food-grade hexane.

Coconut meal
The processing of coconut for edible meal consists of the following steps:
(z) preparation of copra and (zz) removal of oil from copra in screw press and
solvent extraction.
Preparation of copra: Coconut meal is cut into small pieces and dried in a
tunnel drier.
Screw pressing or solvent extraction: Copra thus obtained is pressed in a
screw press. The resulting cake containing about 10% oil is powdered in a
hammer mill. If a fat-free flour is required, the cake is extracted with food-
grade hexane (Narasinga Rao, 1979).

Sunflower seed meal

The processing of sunflower seeds for oil and edible meal involves the
following steps: (z) cleaning and decortication of seed and (zz) screw pressing
and solvent extraction.
Cleaning and decertification: Good-quality sunflower seeds are cleaned of
all impurities. The cleaned seeds are decorticated in a special type of
decorticator.
Screw pressing or solvent extraction: The kernel is pressed in a screw press
to separate oil. The residual cake contains about 10-15% oil. It can be ex¬
tracted with food-grade hexane and the fat-free cake is powdered to pass
through 50 mesh sieve.

Rapeseed meal
Rapeseed contains toxic factors and pungent principles such as allyl
and crotonyl isothiocyanates. It also contains goitrogenic principles. These
will have to be removed in preparation of edible protein concentrate from
rapeseed. The process for preparation of oil and edible protein concentrate
from rapeseed consists of the following steps: (z) cleaning and dehusking,

403
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

(z'z) screw pressing and solvent extraction, (in) treatment of solvent extracted
cake with water for removing toxic principles, and (iv) drying cake in a tun¬
nel drier.

PROTEIN ISOLATES FROM

OILSEEDS AND NUTS

Processes have been standardized for preparation of protein isolates con¬

taining about 85-90% proteins from soybean and groundnut meals. The
process for production of protein isolate from soybean or groundnut con¬
sists o following steps: (z) solvent extraction of edible soybean or peanut
meal, (zi) extraction of proteins with dilute sodium hydroxide at pH 8, (zzz)
precipitation of proteins at pH 4.5 from the extract by the addition of hydro¬
chloric acid, (iv) filtration of proteins and washing with water, and (v)
solubilizing the wet protein in water by the adjusting pH 7.0 and the spray
drying.

Solvent extracted soybean or groundnut meal

Soybean dhal (decuticled soybean) or decuticled groundnut is expressed
in a screw press to remove oil. The cake is extracted with food-grade hexane,
desolventized and powdered to pass through 50 mesh sieve.

Extraction of proteins
The soybean or groundnut cake flour (1 part) is suspended in 15 parts
by weight of water. Concentrated sodium hydroxide solution is added while
stirring till pH increases to about 8.0. The extract is separated using a bas¬
ket centrifuge.

Precipitation of proteins
The proteins in extract are precipitated by adjusting pH of the extract to
4.5 by the addition of hydrochloric acid.
The proteins are separated using a basket centrifuge and washed with
water.

Solubilization of proteins and drying

The wet proteins are suspended in 4 times the weight of water. The pH
is adjusted to 7.0 by addition of sodium hydroxide. The resulting sodium
proteinate is spray dried.

Uses
Protein isolate from soybean or groundnut cake can be used in the
production of vegetable toned milk, infant foods, protein-enriched biscuits
and bread.

404
 BY-PRODUCTS OF OILSEEDS

REFERENCES

Swaminathan, M. 1987. Food Science Chemistry and Experimental Foods. The Banglore Print¬
ing and Publishing Co. Ltd, Bangalore.
Narasinga Rao, M.S. 1989. Beneficiation of byproducts of edible oil industry. (In) Proceedings
of the Second International Food Convention, held at Mysore, pp. 486-82.
Narasinga Rao, M.S. 1979. Vegetable Protein Products in Food Industry. Chemical Engineer¬
ing Education Development Centre, Indian Institute of Technology, Madras, p. 20.

LEARNER’S EXERCISE

1. What do you understand by the word edible oilseed meal?

2. Explain rn detail about the various steps involved in the preparation of soybean meal.
3. Enumerate the process of protein isolates from oilseeds and nuts.

405
 Food
analogue

TEXTURED VEGETABLE PROTEINS

T he proteins from certain oilseeds can be used to make textured prod¬

ucts, which can be used to replace or partly replace meat in a wide
variety of dishes. The seeds most frequently used are of soybean. Defatted
soybean meal contains about 50% protein but it is not suitable as a human
food, because it contains substances which inhibit growth. Some of these
substances are heat-sensitive and are easily destroyed by cooking or roasting.
Others are water soluble and can be removed by soaking and extraction.
Soybean meal can be used to manufacture a product with a meat-like
texture, known as textured vegetable protein (TVP). Textured vegetable protein
is the generic name given to a range of different products from spun fibres
to extruded meat analogues. Texturization involves conversion of powdered
protein into cubes, chunks or granules with ‘mouth feel’ characteristics of
meats (Magnus Pyke, 1982). The protein is extracted by adding an alkali,
and fibres are formed by extruding protein through fine nozzles or
spinnerettes. The fibres are combined with fat, a protein binder, colours
and flavours. The product is similar to cooked meat and can be frozen,
canned or dehydrated. The TVP is being used increasingly in this country,
particularly in industrial canteens and in school meals service. It is also
sold in retail market. Seeds other than soybean used in the preparation of
TVP include sunflower, cotton and groundnut (peanut).
Soya proteins are the most versatile widely used and accepted of the
vegetable proteins. The binding, gelling and emulsifying properties of soya-
protein isolates are particularly useful in many products. Novel methods of
augmenting or dilating meat products using isolate-self-polyphosphate brines
are outlined, including the preparation of restructed meats. Textured flours
(textured soya flour, textured soya protein) are widely used as meat extenders.
Their structure and texture can be modified by varying extrusion parameters
and by addition of salts to the mix before extrusion. Textured flours absorb
water, and to some extent fat, so they can be regarded as having a physical
function in addition to their main role as extenders. Bhoyer et al (1996)
reported that the texturized soya protein (TSP) could suitably be incorporated
in restructured chicken steaks’ formulation up to 20% level without any
adverse effect on the physico-chemical, sensory and microbiological proper¬
ties, and also it was economical to manufacture them.

406
 FOOD ANALOGUE

Spun vegetable protein

During the last 10 years, spun vegetable soya proteins have emerged as
meat replacers, especially in production of dietary and imitation meat prod¬
ucts. These proteins are usually superior in texture and flavour to meat
extenders and have found acceptance among a certain captive clientele.
Preparation of spun protein analogues is to solubilize the protein in a
high-solubility soya flake-flour and then separate the soluble from the in¬
soluble. A common method of commercial separation is centrifugation. The
desired soya protein is separated from the ‘whey’ by collecting the precipi¬
tated protein curd which forms when pH of the clarified liquor is adjusted to
the isoelectric point (pH 4.5) of the protein (Circle, 1951).
The creamy, refined curd is redissolved in alkali to a honey-like viscos¬
ity and pumped through a spinnerette, which is immersed in an acid bath.
The spinnerette is a platinum plate containing several thousand laser-etched
holes. Protein streams coagulate immediately to form somewhat fragile
threads which can be drawn out of the acid bath in the form of the continu¬
ous ribbon or tow, which is heated to adjust their texture or chewability.
The acid in the tow is neutralized and washed out. The white chewy bundles
readily absorb flavours and/or colours and thus serve as an excellent base
material for making muscle bundle analogues.

MEAT AND DAIRY ANALOGUES FROM VEGETABLE PROTEINS

The enormous pressures for protein food products in the coming decades,
brought on by world population increases, will be solved through the exten¬
sion of traditional animal protein foods with vegetable proteins and through
development of food products based on vegetable proteins alone. Analogues
of beef, fish, poultry and other traditional animal protein products, which
are based solely on vegetable proteins, are an established food category,
and are expected to increase market share. Dairy analogues based on veg¬
etable proteins are currently marketed in the form of simulated cow’s milk
and dairy desserts. Vegetable forms of cheese and other milk protein products
are also expected to increase. Nutritional equivalence of vegetable protein
products is fundamental to product design. Protein and fat contents must
be standardized. Vegetable proteins are blended to reach desirable protein
quality. Analogues currently marketed are primarily blends of soya and wheat
proteins containing lesser amounts of yeast and egg albumen. The products
are fortified with vitamins and minerals to levels present in animal protein
foods. Processed meat-manufacturing facilities, which exist in most devel¬
oped countries, can be readily adapted to produce meat analogues. The
technology which has been developed to-date is based on soya or soya/
wheat combinations. The technology can readily be adapted to other vegeta¬
ble proteins such as rapeseed, cotton seed, sesame or sunflower. Meat and

407
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

dairy analogues—high technology, sophisticated food products—hold a share

of today’s market and are projected to gain an increasingly larger percent¬
age of market share as the requirement for protein foods accelerate into the
twenty-first century.
“Analogue” is a food product which is designed as an alternative to
traditional animal protein foods such as meat, poultry, seafood or dairy
products.
The key term in this definition is the word alternative. Analogues are
not merely substitutes for animal protein products but are an entirely sepa¬
rate class of food products.
The analogue will be familiar to the consumer in terms of its functional
characteristics, such as appearance, texture, flavour and colour.

Meat analogues
The earliest meat analogues were developed by John Harvey Kellogg
and presented to his patients in his Battle Creek, Michigan sanitarium, as
early as 1898. These products were based exclusively on wheat gluten which
vas obtained by the washing of starch from high protein wheat flour. More
recently, and particularly since 1955, the pioneering work of Hartman and
Robert blended the proteins from soy, wheat, yeast and egg albumen result¬
ing in products for the Worthington Foods Company. These products were
designed to satisfy the nutritional needs of many religiously motivated veg¬
etarians. These developments formed the base of the present day technol¬
ogy for the manufacture of meat analogues (Thomas, 1979).

Dairy analogues
The most widely known examples of dairy analogues are margarine,
whipped toppings and non-dairy coffee whiteners. These products have
achieved world-wide success in the market place in the last 30 years. Dur¬
ing this same period, the simplest of the dairy analogues, simulated cow’s
milk, has been marketed for infants who exhibit allergic reactions to bovine
product. Using this technology as a base, analogues of cheese, ice-cream
and other milk-based desserts have been developed (Thomas, 1979).

DESIGN OF MEAT ANALOGUES

The greatest challenge to the food technologists in the design of these so¬
phisticated food products is in the area of taste and texture. Manufactured
of meat analogues parallels very closely to those of processed meat, such as,
bologna, salami, pre-cooked sausage and frankfurters. However, when the
raw materials are vegetables in their physical characteristics, particularly
regarding taste, they are extremely difficult to flavour. Many of the major
flavour houses in the world have aggressive research programmes designed
to develop meat flavours which will be used to impart flavour of animal

408
 FOOD ANALOGUE

protein to the vegetable protein bases. Significant progress has been made
in several areas, particularly those of pork, bacon, ham and beef fat. Appro¬
priate artificial seafood flavours are currently receiving a great deal of atten¬
tion but so far are lagging behind, particularly in terms of their ability to
withstand even the mildest of processing conditions.

NUTRITION

Vegetable protein analogue products, because they may include almost any
nutritional attribute, can clearly be designed to correct or improve nutri¬
tional qualities inherent in a diet based largely on animal protein products.
For example, meat analogues contain no cholesterol and can have a favour¬
able polyunsaturated: saturated fat ratio. Moreover, the protein levels can
be increased if this is desirable. The fat levels are almost always reduced for
the products. This results in less caloric density, an attribute widely sought
in products utilized in weight-reduction diets. The micronutrient contents
of analogues are carefully controlled. Vitamins and minerals can be added
to the products at virtually any level.

REFERENCES

Bhoyer, A.M., Pandey, N.K., Anand, S.K. and Verma, S.S. 1996. Development of restructured
chicken steaks using texturized soya proteins as extender. Indian Food Packer 50(4):
15-18.
Circle, S.J. 1951. Soybean and Soybean Products, vol.l, 336 pp. Markely, K.S. (Ed.). Inter-
Science, New York.
Magnus Pyke. 1982. Food Science and Technology. Deh Hua Printing Press Co. Ltd, Hong
Kong.
Thomas, L.W. 1979. Meat and Dairy Analogs from Vegetable Proteins, (in) Proceedings of World
Conference on Vegetable Food Proteins, held at Amesterdam, the Netherlands (29 Octo¬
ber-3 November), vol. 56, No. 3, pp. 404-406.

LEARNER’S EXERCISE

1. Write in short about the texturized vegetable proteins and spun vegetable proteins.
2. Write about meat and dairy analogues from vegetable proteins.

409
32. Fermented
soya products

M ain fermented vegetable protein foods in Japan and China are soy-
sauce (shoyu in Japan, chiang-yu in China), fermented soy paste (miso
in Japan, chiang in China), safu, and natto, which are all traditional foods.
Chiang, which originated in China some 2,500 years ago, was introduced
into Japan during the seventh century and transformed into the present
Japanese shoyu and miso, which are now quite different from their Chinese
counterparts. Their fermentations consist of koji fermentation by Aspergillus
species and subsequent by brine, which contains lactic acid and alcoholic
fermentations. The characteristic appetizing aroma observed in Japanese
style of soy sauce (shoyu) is derived through a special brine fermentation
from the component of wheat which constitutes about one-half of the mate¬
rials. During the recent 2 decades, the fermentation technology and engi¬
neering on shoyu and miso have made great progress in Japan. Sufu (Chinese
soybean cheese) is a cheese-like product; originated in China in the fifth
century. It is made through the fermentation by Mucor or a related mould
from soybean protein curd called tofu, which is made by coagulating soy
milk. This product is widely manufactured in China on a small scale, but it
is not made and consumed in Japan. On the other hand, natto is the fer¬
mented soybean protein food common in Japan. It is a whole soybean prod¬
uct fermented by Bacillus species, and has originated in north-eastern Japan.

MISO

The Japanese fermented soya paste miso is now manufactured commer¬

cially in modernized factories on a large scale. There are many differences
in the way fermented soybean pastes are consumed in Japan and in China.
In China, chiang is used as the base for sauces served with meat, sea food,
poultry, or vegetable dishes. In Japan, however, miso is mainly used as the
base for soups. The average annual consumption of miso is 7.2 kg/ person
in Japan.
The manufacturing methods for miso differ by the type of miso, but the
basic process is all the same as shown in Fig. 67 for rice miso which is the
most popular miso (Fukushima, 1979).
Miso can be classified into 3 major types (rice miso, barley miso, and
soybean miso) on the basis of the raw materials. Rice miso is made from

410
 FERMENTED SOYA PRODUCT

Fig. 67. Manufacturing process for rice miso

rice, soybean, and salt; barley miso is made from barley, soybean, and salt;
and soybean miso is made from soybeans and salt. These types are further
classified by the taste into 3 groups, viz. sweet miso, semi-sweet miso, and
salty miso. Each group is further divided by colour into white-yellow miso
and red-brown miso. Among these miso, rice miso is the most popular one,
forming 81% of the total miso consumption.
The manufacturing methods for miso differ by type of miso, but the
basic process is all the same, as shown in Fig.67, for rice miso. There are 2
basic differences between the miso and shoyu manufacturing, though both
are very much alike. One is in koji-making. The koji of shoyu is made by
using all the raw materials, that is, the mixture of soybean and wheat,
whereas the koji of miso is made by using only carbohydrate materials, that
is, rice or barley. The soybean is used in miso making without the inocula-

411
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

tion of koji mould, except on soybean miso. The other difference is that miso
is a solid paste, and therefore the making process has no filtration step,
which has a very large influence on the cost in shoyu-making. The fungus
and yeast used in miso manufacturing are very similar and sometimes the
same as in shoyu manufacturing.
Recently, a revolution has occurred in the manufacture of miso, which
has taken the form of automated equipment and continuous processing.
Particularly, the use of a rotary fermenter is used in preparation of rice or
barley koji. Cooked and mould-inoculated rice is put into a large trommel of
this rotary fermenter in which the temperature and moisture-controlled air
is circulated. The trommel is rotated several times to prevent rice from ag¬
glomerating during fermentation. After completion of fermentation, the re¬
sulting koji is mixed with salt, cooked whole soybeans, pure cultured yeasts,
lactic acid bacteria, and water, and then kept for an appropriate period for
the second fermentation. The resulting aged mixture is mashed and pack¬
aged as miso.
Miso is a food prepared by a 2-step fermentation process. The first step
involves fermentation of rice to produce enzymes, followed by a second fer¬
mentation of the mould rice or koji along with soybeans, salt and suitable
inoculum.

TEMPE

Tempe is the name ordinarily used for soybean-fermented product and is

termed Tempe-kedale. Tempe is the name to describe the most impressive
fermented food nationally adopted for improving nutrition and health of the
children in Indonesia. Tempe, a popular traditional food, had originated
hundred years ago in Java as fermented soybean cake. Of all fermented
foods, Tempe with its high rating in sensory value, nutritional benefits and
low cost and simple process technique, appears to be the most valuable food
for common people, especially, children, women and under-nourished. It
has many functional properities comparable to egg and cheese in cooking,
binding, emulsifying and low bulk and high nutrient density food (Vaidehi,
1993).
Tempe is a product in which mycelia of mould (Rhizopus oligosporous)
provide the meat-like texture. Tempe is likely to have high public attention
as bio-technical industrial food, especially in the prevailing occurrence of
orteriosclerotic cardiovascular diseases. It might replace the main course of
dishes like meat and eggs and contribute greatly to lower saturated fat content
of the diet. This product contains no cholesterol and further works as a
cholesterol reducer as it is rich in unsaturated fatty acids. Traditional method
of its preparation with soybean is given in Fig. 68.

412
 FERMENTED SOYA PRODUCT

Soybean whole (1 kg)

I
Clean and wash
i
Boil (30 min.)
*i
Wash and soak overnight (17 hr)
i
Dehull (remove hulls on floatation in water)
i
Steam for 45 min. (until cooked but not too soft)
l
'k

Surface dry
I
Mix well with 25 ml (1 1/2 tablespoon) of vinegar
in a vessel (adjust pH 4.0-4.5)
Ti
Inoculate (2 g tempe culture kg soybean)
I
Pack evenly in perforated polythene pouches and seal
I
Incubate in humid and warm place (40 hr), 32° to 36°C
I Chips
Fresh tempe Toffees
I Curry, Koftas
Slice, steam blanch (15 min.)
i
Dehydrate (70°C) in oven/sun-dry
I
Powder into desired grit size, pack in polythene pouches for
future use
I
Second generation tempe products (porridge, soups, cookies,
halwas, chapati, etc.)
I
Tempe can also be prepared with foodgrains other than
soybean like maize, cowpea, groundnut etc.

Fig.68. Tempe - Kedale (soybean) process

Changes in soybeans during tempe preparation

Hessettine (1965) reported following changes in soybean during tempe
preparation.
Proteins: Large amounts of proteins are broken down into simple amino
acids. Total nitrogen remains about the same, but soluble nitrogen greatly
increases. Ammonia is produced in last stages of fermentations.
Lipids: One-third of the neutral fat is hydrolysed to palmitic, stearic,
oleic, linoleic, and lmolenic acids. Rhizopus uses only linolemc acid. Total
fat remains relatively constant.
Carbohydrates: Reducing sugars decrease. The pH changes little towards
alkaline side. Hemicelluloses decrease.

413
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Koji making
process

Brine
fermentation
process
Fermented

4
Pressed

I- » Cake

Raw soy sauce

1
Refining
process Pasteurized

i
Koikuchi-shoyu

Fig.69. Manufacturing process of Koikuchi-shoyu

Enzymes: Proteases and lipases are present in large amounts and amylases
and pectonase in small amounts. Fermentation loss in dry weight is about
4%. Moisture content of produce is 55-65% and total water-soluble solids
increase during fermentation.
In preparation of tempe, a mixed culture Rhizopus oligosporous and
R. oryzae is used for bringing about fermentation. The resulting tempe con¬
tains tender cooked soybean bound together by a dense cottony mycelium
of Rhizopus mould in a compact form like cake or in patties form. Tempe
cake is cut into slices or cubes which are used in the preparation of curry,

414
 FERMENTED SOYA PRODUCT

Soybean (90%) Wheat (10%) Salt

i i
Koji making
Cooked Roasted and crushed
process
i
Mixed and<- Seed mould
extruded

I
Incubated

i
Koji

i Brine

Moromi-mash

Brine fermentation
process

Fermented

i
Filtered

Residue

i
Washed
Refining
process Mixed

i
Tamari-Shoyu

Fig.70. Manufacturing process of tamari-shoyu

chips and toffees etc. Otherwise after dehydrating make it into powder form.
It could be blended into various Indian preparations.

SOYA SAUCE

The koikuchi-shoyu represents the largest production of Japanese soy sauce.

The forerunner of this type of soy sauce had been created in the 17th century
and has been improved into the present product. It is an all-purpose sea¬
soning, characterized by a strong aroma, myriad flavour, and is deep brownish
red in colour. The second type of soy sauce is koikuchi-shoyu, characterized

415
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

by a lighter brown colour and milder flavour. It is used mainly for cooking
when one wishes to preserve the original flavour and colour of the foodstuff
itself. The other 3 types of soya sauces are produced and consumed only in
isolated localities for special uses in Japan. On the other hand, the soy
sauce traditionally produced in China is a tamari-shoyu which forms only
2.2% of the total production of fermented soy sauce in Japan. This Chinese
style of soy sauce is characterized by a deep dark colour, thick taste, and
poor aroma. The difference in aromas observed between Japanese and Chi¬
nese styles of soy sauce are ascribed to different ratios of wheat and soybean
used. As seen in Figs 69 and 70, the Japanese style of soy sauce uses much
more wheat, and its characteristic aroma compounds are produced mainly
from wheat constituents through koji fermentation, alcoholic fermentation,
and other special fermentations. Further, an additional, subtle, pleasant
aroma is produced through the pasteurization process, as explained later.
The Japanese fermented soy paste miso is now manufactured commer¬
cially in a modernized factory on a large scale. There are large differences in
the way fermented soybean pastes are consumed in Japan and China. In
China, chiang is used as the base for sauces served with meat, seafood,
poultry or vegetable dishes. In Japan, however, miso is mainly used as the
base for soups. While the average annual consumption of miso is 7.2 kg/
person in Japan, 80-85% of this consumption is consumed in the prepara¬
tion of miso soup, and the balance is used as seasonings for various type of
foods.
There are many varieties of miso in Japan as well as of chiang in China
based on the ratio of substrates, salt concentration, the length of fermenta¬
tion and aging. Most of miso in Japan is a paste which resembles groundnut
or peanut butter in consistency and it is smooth in texture. Its colour varies
from a creamy yellowish white to a very dark brown. Generally speaking,
the darker the colour, the stronger is the flavour. The product is typically
salty and has a distinctive pleasant aroma.

SOYBEAN CHEESE (SUFU)

Sufu is a soft cheese-type product made from soya milk curd by the action
of micro-organisms. Sufu had originated in the fifth century in China and
has been widely consumed as a relish by Chinese people. However, sufu is
not consumed in Japan.
Sufu-making process consists of 3 major steps, viz. preparation of soy
milk curd, moulding process, and brining process. The first step, that is,
soya milk curd-making is essentially the same process as used for making
tofu. Tofu can be consumed directly and is widely eaten throughout the Far
East. In the case of making sufu, however, tofu is made so hard that its
water content may be less than 70%, while the water content of directly
consumed ordinary tofu is about 90%.

416
 FERMENTED SOYA PRODUCT

The second process of sufu making is the moulding process. After the
hard-made tofu is cut into 3 cm cubes, the cubes are heated for pasteurization
and for reducing water content of the cube surface, and then the mould is
inoculated on it. The moulds belonging to the genus of Mucor or Actinomucor
are usually used, and the moulds belonging to the genus of Rhizopus are
also used sometimes. For instance, Actinomucor elegans, Mucor hiemalis,
Mucor silvaticus, Mucorpraini, Mucor subtilissimus, and Rhizophus chinensis,
are used for the inoculation. The time of mould fermentation differs, de¬
pending on the varieties of moulds. It takes about 7 days at 12°C for Rhizopus
chinensis, 3 days at 24°C for Mucor hiemalis and Mucor silvaticus, and 2
days at 25°C for Mucor praini.
The last process of sufu-making is brining and aging. The freshly moulded
cubes are placed in various types of brining solutions depending on the
flavours desired. The usual brining solution consists of salted fermented
rice mash, soya sauce moromi mash, fermented soya paste or 5% NaCl
solution containing rice wine having ca. 10% ethyl alcohol. The time of ag¬
ing ranges from 1-12 months, depending on the varieties of the brining
solution. Finally, the product is bottled with the brine, sterilized, and mar¬
keted as sufu.
Sufu is a creamy cheese type product which has a mild flavour, and
therefore it would be suitable for western people in using it the same way as
cheese.

REFERENCES

Fukushima. 1979. Fermented vegetable (soybean) protein and related foods of Japan and
China. Journal of American Oil Chemists Society 56: 357-360.
Hesseltine, C.W. 1965. A millennium of fungi, food, and fermentation. Mycologia 7(2): 149-
197.
Vaidehi, M.P. 1993. Tempe - A Unique Food for Nutrition and Health Benefits. Biotechnology
in Foods, Serial No.l, University of Agricultural Sciences, Bangalore.

LEARNER’S EXERCISE

1. What is miso? Write about manufacturing process of rice miso.

2. Explain in detail about tempe process.
3. Explain in detail about changes in soybean during tempe preparation.
4. Enumerate manufacturing processes of koikuchi-shoyu.
5. Write short notes on the following: (a) Soya sauce; (b) Tofu; (c) Shoyu.

417
33. Irradiated and
radiated foods

F ood preservation by irradiation has unique merits over conventional meth¬

ods in retaining flavour, texture, colour etc. of fresh foods. Irradiation
tratment can replace chemical preservatives and fumigants, is less energy
demanding, improves hygiene, and is applicable to pre-packed items. The
application of low-dose treatment for insect disinfestation of grains, sprout
inhibition in root crops, delayed ripening in some fruits, elimination of stone
weevil in mango; medium-dose for reduction of microbial load including
spoilage organisms and some pathogens (Salmonella) in frozen sea-foods
and meat; and high-dose for sterilization of spices, have commercial signifi¬
cance.
Food irradiation, unlike other methods of food preservation, does not
leave any trace of its effects in observable physical characteristics of the
product and hence has to be performed only at source at governmental
licenced irradiation facility to ensure good irradiation practice.
Radiation processing is recognized as capital-intensive, and hence ef¬
forts are being made to develop cost-efficient systems, tailored for commod¬
ity-wise applications and requires integration of such units initially into the
prevailing practice of harvest, storage and distribution (Nodkerni, 1989).
The Ministry of Health and Family Welfare, ammended in 1994, the
prevention of Food Adultration Rules of 1955 through a Gazette notification
dated 9 August 1994. This permits irradiation of onions, potatoes and spices
for internal marketing and exports (Lai Kaushel et al, 1996).

ALPHA, BETA AND GAMMA RADIATIONS

In 1899, it was shown independently by several researchers that the

radiations of uranium compounds could be deflected and resolved in part
when under the influence of strong magnetic fields. The portion not affected
by the magnetic field was observed to be capable of traversing thick layers of
matter. The entire undeflected part was at first termed alpha radiation. The
deflected part of the radiation behaved like electrons and was termed beta
radiation. In 1903, Rutherford demonstrated that if the applied magnetic
field was strong enough, the alpha radiations could also be deflected, and
behaved as if positively charged. At almost the same time, however, it was
found that a portion of the alpha radiation, was highly penetrating and was

418
 IRRADIATED AND RADIATED FOODS

undeflected in even the strongest magnetic field. This component was termed
gamma radiation and was found similar to X-rays. The alpha rays were
ultimately shown to be a particle of matter consisting of a helium atom
stripped of the outer electrons and hence a positively charged nucleus; the
beta particle a high energy electron and negatively charged; and the gamma
radiation a non-corpuscular electro-magnetic radiation of extremely short
wave length. Among other ionizing radiations of importance, subsequently
classified, were protons, single positively charged hydrogen nuclei; and neu¬
trons, electrically neutral particles with mass of a hydrogen nucleus.

Radioactive decay
Radioactive elements constantly decay, or lose radioactivity. The time
required for a substance which is radioactive to lose 50% of its activity is
termed as half-life of the radioisotope. This decay is an example of a statistical
process, i.e. the number of particles undergoing a reaction is proportional to
the number of such particles present. The decay of radium is such that half
the radium disappers in approximately 1,600 years. Thus, starting with 1 g
radium, in 1,600 years only 0.5 g would remain. In the following 1,600
years, only one forth of 1 g would remain. The decay rate of a radioactive
element is defined by its half-life, the time required to decompose such that
only one-half remains.
The interesting fact about radioactive decay is that the decay time of a
radioactive substance is independent of temperature, pressure, presence of
catalysts or other factors commonly influencing chemical reactions. All evi¬
dence available indicates that this decay is absolutely constant for a particular
radioisotope.

Units of radiation
Measurement of radiation involves intensity of source (characteristic
solely of the source), cumulative effect on the substrate, and rate at which
the effect is brought about. The source is characterized by the nature and
energy distribution of the radiations, and how fast the radiation is being
emitted (1 curie equals 3.7 x 1010 disintegrations/sec.). The original roent¬
gen was defined in terms of ionization events but has conceptual difficul¬
ties. The rad is more useful because it is a unit based upon energy absorbed
(100 ergs/g), which is measurable.

SAFETY OF IRRADIATED FOODS

The research and development work over the years on radiation preserva¬
tion of foods has involved substantial inputs of basic information to answer
all possible questions relating to the efficacy of the treatment, quality of the
materials and the safety of the irradiated foods for human use. Food is the
most essential aspect for the existence of all living beings. On the other

419
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

hand, anything relating to the nuclear energy could cause concern. The
safety of irradiated foods for human consumption has received utmost at¬
tention nationally and internationally. The WHO has endorsed the view that
any item of food exposed to radiation up to 1 megarad is safe for consump¬
tion and does not need any toxicological evaluation. The doses required for
extending the storage life of most foods are far below this stipulated limit.
The radiation chemistry of major foods does not present any microbial haz¬
ards due to harmful mutants.
After WHO recognized the safety of irradiated foods in 1980, the British
Government appointed an Advisory Committee on Irradiated and Novel Foods
(ACINF) to review independently the scientific data on the safety, with a
view to allowing flexibility to the existing prohibitory regulations in that
country, since irradiated products were making their way into the UK from
the neighbouring European countries. The ACINF recommended in 1986
that irradiated foods are safe. The studies carried out recently in China with
human volunteers have dispelled all scientific hesitations in respect of irra¬
diated foods. The Food and Drug Administration (FDA) has permitted in
1986 the treatment of spices at doses up to 3 megarad, 3 times the dose
limit cleared by the WHO (FDA, 1986).

PURPOSE OF IRRADIATION

It is recognised that the radiation treatment of foods can help achieve a

number of objectives with distinct advantages which include: (a) it replaces
use of hazardous chemical preservatives and fumigants; (b) process is less-
energy demanding; (c) it improves food hygiene; and (d) it is possible to
apply radiation to pre-packed items. Exposure to gamma-radiation does not
leave any radioactivity in the materials. The use of fumigants like ethylene
dibromide has been banned or discouraged by some countries, and many
more are becoming conscious of the hazards of chemical treatments. The
combinations methods using radiations along with the conventional proce¬
dures also have shown promise for improving hygienic quality of even the
processed products like chapaties, papads etc.
The purpose of irradiation is different with each commodity and in¬
volves (a) low dose treatment for insect disinfestation in grains etc. and
sprout inhibition in root crops; (b) medium-dose treatment for reduction of
microbial load including spoilage organisms and some pathogens as in sea¬
foods and meat; (c) high-dose treatment to attain sterilization as in spices;
and (d) releases high temperature of the product irradiated and makes food
preservation possible in the uncooked state.

Sprout inhibition in potato and onion

The application of low doses of radiation (< 15 kilorads) can arrest sprout¬
ing of potato and onion. As a result, storage losses due to sprouting of the

420
 IRRADIATED AND RADIATED FOODS

tuber and bulbs and their dehydration can be reduced substantially. Adop¬
tion of the new technology, especially for the onion, could mean significant
benefits to India which is among the largest producers of onions in the
world.
The development of high-yielding, short duration and disease-resistant
varieties of potato in recent years has led to increased production and con¬
sequently problems of storage and conservation. Chemical sprout inhibitors
are difficult to apply and are not always effective. Sprout-inhibiting dose of
radiation is also effective in destroying tuber moth, a devastating pest of
potato. Irradiation, therefore, offers a satisfactory solution to the storage
problems of potato. To arrest sprouts in onion and potato, low doses of
radiation (0.15 kilo Guy) are applied on the product. The process is rela¬
tively simple. Food travels on conveyor through a chamber where dozens of
‘pencils’ usually made from cobalt 60 and scaled in stainless steel tubes,
irradiate food with gamma rays.
Radiation dose is measured by the unit Guy (Gy). International health
and safety authorities have endorsed the safety of irradiated foods up to
dose less at 10 kilo Gy, which is 100 to 150 times higher than the dose
required (0.15 kilo Gy) for inhibition of sprouting in onion.

Delaying ripening of fruits

Low doses of radiation (<50 kilorads) are effective in delaying the natu¬
ral processes of ripening in fruits. Thus, shelf life of mango can be extended
by about a week and that of banana up to 2 weeks. This could improve the
scope for internal trade and augment export of these commercially impor¬
tant fruits of India. Furthermore, gamma radiation can eliminate the seed
weevil, an insect that lodges deep inside the stone of the mango. This can be
a satisfactory solution to a vexing quarantine problem.

Disinfection of grains
The success of green revolution has enabled India to produce more than
190 million tonnes of foodgrains every year. However, inadequate storage
facilities lead to losses, of 10-15% every year, due to pest alone. With pro¬
gressive increase in the quantity of foodgrains and necessity for longer stor¬
age periods, these losses will escalate unless disinfestation measures are
improved. Chemical disinfestation methods, such as fumigation, require
repeated applications as these do not eliminate insect eggs. They may also
leave harmful residues in the treated grains. Low-dose irradiation completely
kills or sterilizes the common grain pests and even the eggs deposited inside
the grains. Moreover, only a single radiation exposure of grains is sufficient
for disinfection. This, therefore, is ideally suited for large-scale operations,
thereby offering substantial economic benefits. Irradiation can also serve as
an effective process for disinfestation of certain prepacked cereal products
like atta, suji (rava) and premixes.

421
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Preservation of seafoods
Fish is an important source of animal protein, available in plenty all
along the 5,000 km Indian coastline. However, the existing inadequate pres¬
ervation facilities cannot cope with the rapid spoilage of the catch and thereby
limit the availability of sea foods in the interior regions.
By selective destruction of spoilage bacteria, moderate doses (200
kilorads) of radiation can extend the acceptability, and in turn, marketabil¬
ity of iced fish by about 2 weeks. Combination processes with heat and
radiation can also increase the shelf life at room temperature by several
weeks. Besides, this is the only method for removal of pathogens from
prepacked frozen product.

Microbial decontamination of spices

India is a major spice producing and exporting country. Spice export
trade is always faced with stringent quality requirements relating to insect
Table 44. Food irradiation product and process specifications

Product Process Dose Dosimeter Package Storage Estimated

(rads) requirements temperature useful
(°C) and RH storage life

Potato Sprout 7,500 Ferrous Stored in open 5.85% RH 2 years

inhibition sulfate containers or or more
in porous 20 10 months
containers or more
Flour Insect 50,000 Ferrous Sealed paper or Room 2 years or
destruction sulfate cloth bags, and temperature more
overwrapped to or 4.4 5 years or
to prevent more
reinfestation
Berries Pasteurization 150,000 Cobalt Sealed in oxygen, 1.1 21 days or
(mould glass C02 permeable film more
destruction)
Sliced meat Pasteurization 1,000,000 Ferric Sealed in gas-proof 60 days or
and fish (bacteria, sulfate container more
yeast, mould
parasites)
Animal, fish Heat 4,500,000 Ferric Vacuum sealed in Room 2 years or
and inactivation sulfate durable container temperature more
vegetable of enzymes (tin can) with
tissue (74°C) odour scavenger
Radiation 0 5 years or
sterilization more
Fruits Heat 2,400,000 Ferric Vacuum sealed in Room 2 years or •
inactivation sulfate durable container temperature more
of enzymes (tin can) with
(74°C) odour scavenger
Radiation 0 5 years
sterilization

422
 IRRADIATED AND RADIATED FOODS

infestation and microbial contamination. Fumigation of spices with chemi¬

cals like methylbromide, ethylene oxide and propylene oxide, has inherent
disadvantages, especially of the retention of chemical residues. Single treat¬
ment of gamma radiation (< 1 Mrad) can make spices free of insect infesta¬
tion and microbial contamination without the loss of flavour components.
The treatment can also be used for ground spices and curiy powder prepacked
in cartons. Summary of irradiation product and process specifications is
given in Table 44.
There are many advantages of irradiation.
• Storage losses due to sprouting and dehydration can be reduced
substantially.
• Shelf-life of certain fruits could be extended.
• Foodgrains c^n have better quality.
• Free of grain pests.
• Huge amount of sea food can be prevented from going waste by
selective destruction of spoilage bacteria.
• Single treatment of gamma radiation makes the spices free of in¬
sect infestation, which is a better method than fumigation with
chemicals.

INTERNATIONAL EFFORTS

According to the available information several countries have now accorded

clearance to more than 40 items of irradiated food. Some of these, including
the USA, former USSR, the Netherlands, Japan, France, Hungary etc., have
taken steps to commercialize the food irradiation process.
The export trade is always faced with stringent quality requirements
relating to insect infestation and microbial contamination in spices. Irradi¬
ated spices are cleared in several countries which essentially import these
commodities. Commercial irradiation facilities have also been set up in vari¬
ous countries including the USA, Canada, France, Japan, the Netherlands,
the former USSR etc. At the port of Odessa in the former USSR, an indus¬
trial radiation disinfestation plant has been in operation since 1980 for treat¬
ment of imported grains before distribution within the country. Japan has
been irradiating potato on commercial scale since 1973.
The incidence of Salmonella sp. in sea foods and meat has caused a
world wide concern. Contamination with pathogen Salmonella has affected
the international trade in frozen sea foods and meat products. No treatment
other than radiation is available for the elimination of Salmonella from the
frozen products. The frozen sea foods like shrimp are imported by the Neth¬
erlands from India and other Southeast Asian countries and re-exported to
other countries after irradiation to remove pathogens like Salmonella.
Food irradiation methodology gained acceptance in the USA, Canada

423
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

and some European countries because of the awareness of the hazards

caused by toxic residues left by chemical fumigants and insecticides. The
US Environmental Protection Agency has banned the use of ethylene
dibromide and ethylene oxide and other fumigants. However, these are used
in our country as a routine practice. Recently, the US importers detected
presence of ethylene dibromide in pepper exported from Kochi and the Spices
Export Promotion Council had to experience concern because of this.
The international trade in irradiated items of food is to be regulated by
a code of practice evolved by FAO/WHO Codex Alimentarius Commission. It
would, therefore, be possible to promote trade with countries which have
adopted the Codex standards.
The Government of India has accorded approval in principle to the use
of radiation technology only after the Ministry of Health and Family Welfare
was thoroughly convinced of the safety of the process. The Ministry has
selected initially the items like spices and frozen shrimp, meant for export
for the application of this methodology. It is obvious that foods are not only
stored longer but also their hygienic quality is improved.

PRELUDE TO COMMERCIALIZATION

Food irradiation is among the most intensively investigated subjects com¬

pared to any other method used for preserving food. The methodology is
now at the stage of application. For actual commercialization, the Govern¬
mental acceptance is necessary to ensure confidence of the users. The ulti¬
mate purpose of food regulations is the protection of the health and safety of
the consumer and to prevent unethical practices in the trade. The regula¬
tory agencies dealing with food quality need to issue authorization before an
item is allowed in the market. This would be particularly applicable to most
of the processed foods involving the use of chemical additives either for
preservation or for making the product more attractive with colouring and
flavouring agents. It is possible to detect and identify food additives for regu¬
latory purposes with the use of easy methods. However, sufficiently simple
methods are not available for foods exposed to radiation. Also, unlike other
physical treatments, such as freezing, canning, drying etc., irradiation does
not leave any trace of its effects in observable physical characteristics of the
product. It is, therefore, obvious that the control of food irradiation can be
performed only at a source at the licenced irradiation facility to ensure good
radiation practice. As far as the quality of the material is concerned, it is
either marketable or spoilt for human use.
Radiation processing is recognized to be capital intensive. The users
particularly the traders will be attracted only if the costs are favourable to
allow them sufficient margin of profit. The precise figures are available on
the total production of agricultural commodities, but it is difficult to obtain

424
 IRRADIATED AND RADIATED FOODS

actual estimates of the extent of the wastage. This factor alone could tilt the
balance towards favourable economics, particularly in the tropical countries.
Before embarking on commercial practice, efforts are being made to
develop cost-efficient systems. The irradiation facilities perhaps will have to
be tailored for commodity-wise applications, by integrating such units ini¬
tially into the prevailing practice of harvest, storage and distribution, since
the production centres are distributed in various parts of the country. The
purpose of treatment and the dose range requirements also differ with each
item as stated above. The installation and operation of irradiation facilities
are strictly determined by the safety regulations, to protect the health of the
users as well as the operators.

REFERENCES

FDA. 1986. News release (p 81-6) Mear. 27 U.S. Department of Health. Serv., Washington,
D.C.
Lai Kaushal, B.B., Thakur, K.S. and Thakur, N.S. 1996. Priliminary studies on use of new
packages for packaging and transportation of starking Delicious apples. Indian Food
Packer 50(2): 27-35.
Nadkarni. 1989. Radiation preservation of foods—potentialities and prospects. Proceedings of
the second International Food Convention held during 18-23 February at Mysore; or¬
ganized by Association of Food Scientists and Technologists, CFTRI.

LEARNER’S EXERCISE

1. Write short notes on the following:

(a) Radioactive decay; (b) Unit of radiation; (c) Alpha, beta and gamma radiations.
2. Write about safety of irradiated foods.
3. Explain in detail about advantages of irradiation.
4. Radiation processing is recognized to be capital intensive—Discuss.

425
.
Food packagi
 Packaging
material

T oday almost all foods reaching the customers are packaged. Much of the
food packaging is in rigid or semi-rigid containers made of metal glass,
plastics, paper and paper-board or combinations of such materials. Rigid
containers have the most favourable properties, such as protectiveness, im¬
permeability, and ease of sterilizing. In addition, they are easily adopted to
high-speed equipment for making, filling and handling. Foods in hermetically
sealed containers are protected from environmental damage by micro-or¬
ganisms, moisture, oxygen and light. The primary objectives of food packag¬
ing are to provide protection from spoilage, ease in distribution, display and
handling; communication between the manufacturer and customer; and
motivation of customers to buy again. Taylor (1966), Preston (1967) and
Robertson (1993) presented information on packaging of foods in various
types of containers.
The major categories of metal containers are cans, boxes, collapsible
tubes, aerosols, cups and trays formed from sheet metal. Tinplate is one of
the most important packaging materials used in the production of metal
containers. Tinplate excels in various characteristics, including strength
and corrosion, resistance, solderability, magnetic-handling capability, pos¬
sibility of recycling, and cost competitiveness. Over the past decade the tinplate
industry has been characterized by many innovations including differen¬
tially electrolytic tinning, double reduce technique, draw and iron forming,
etc., which have greatly enhanced its competitive strength with other can¬
making materials such as aluminium and the so-called tinfree steels.
Another trend is the growth of the glass container industry in food pack¬
aging. A very wide range of food products are brought to market in glass.
Some reasons for the use of glass are that it is chemically inert to foods; its
transparency is an important factor for impulse selling, it does not deterio¬
rate, and provides strength, rigidity and long shelf-life. With proper closure
it makes opening and reclosing easy; and it is the most easily recyclable of
all packaging materials. The major categories of glass packages are bottles,
jars, tumblers, jugs, vials and ampules, used in packaging foods, bever¬
ages, drugs and household products. The upward trend of glass-container
production in this country was resumed in 1992 with a record total exceed¬
ing 2 billion dollars.
For package planner, there is another growing field to consider, viz.
rigid plastic containers for foods. Virtually every type of rigid or semi-rigid

429
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

container produced from metal, glass or paper-board can be made from

plastics. There are more than a dozen types of resins available for moulding
in a wide range of grades and formulations. The most widely used are
polyethylene, polystyrene and vinyl. New resin formulations and bottle-blow¬
ing methods are still being developed. For high-barrier application, important
packaging materials are the new acrylonitrile based resins. The major cola
bottlers, Pepsi and Coca-Cola, are both continuing their respective test pro¬
grammes with these high-barrier application. Acrylic multipolymers are
another new approach in hot-filling and high-oxygen barrier applications.
Polypropylene co-polymers have also demonstrated their good characteristics
in hot-filling and contact clarity. These 2 factors, plus satisfactory barrier
properties, processibility and favourable costs, have enabled polypropylene
to virtually sweep the pancake syrup field.
Packaging of foods is not only restricted to protecting them from
deteriorations, although this is its most important function. It serves several
other purposes (Corlin etal, 1990; Upadhyay etal., 1994) which include:
(a) Convenience: Mass production of uniform articles. Standard pack¬
age convenience for storing and transportation.
(b) Avoidance of loss: Milk distribution (avoiding contamination) avoid¬
ing dishonest shortage weight.
(c) Brand confidence: Consumers like to purchase standardized food
in well-packaged carton of breakfast cereal or margarine.
(d) Machines: Machines available for packaging foods have been elabo¬
rated to a remarkable extent. Automatic equipment can be pro¬
vided for filling bottles, cans and jars with measured quality of liquids
and semi-liquids such as sauces and mayonnaise and for capping
the containers. Vaccum-operated machines can be purchased for
the high speed packaging of powders such as dried milk or custard
powders.
Food packaging serves needs of marketing and also helps preservation
of foodstuffs especially processed ones. Food packaging employs a variety of
materials. They are (a) rigid metal as in cans and drums; [b) flexible metals
as in aluminium and tin foils; (c) glass as in jars and bottles; (d) rigid and
semi- rigid plastics as in containers and squeeze bottles; (e) flexible plastics
as in pouches, wrappers; If) rigid cardboard, paper and wood products as
in boxes; (g) flexible papers as in boxes as in bags and laminates; (h)
multilayers which may combine paper, plastic and foil. Packaging of foods
has become very complex, and considerable research and development efforts
are being made to provide better and cheaper packaging material and
methods.
The food packaging containers should satisfy a number of requirements.
The more important requirements and functions are (i) non-toxic, (ii) sanitary
protection, (in) moisture and fat protection, (iv) gas and odour protection,
(v) light protection, (vi) resistance to impact (vii) transparency, (viii) tamper
 PACKAGING MATERIAL

proof, (ix) ease of opening, (x) pouring features, (xz) reseal feature, (xzz) ease
of disposal (xz'zz) size, shape and weight limitations, (xiv) appearance and
printability, {xv) low cost, (xz;z) special requirement if any.
Food containers are broadly divided into (a) primary and (b) secondary
containers. In case of foods like milk products, dried eggs, fruit concentrates,
they are filled into plastic liners which are called primary containers. These
are packaged within cartons which are called secondary containers. In case
of nuts, oranges etc., they are packaged straight into secondary containers
like box or drum to hold the units together. In general primary containers
have to satisfy many of the above mentioned requirements (Harris and
Loeseck, 1960; Sacharaw, 1980)

TYPES OF CONTAINERS

Tin cans
Tin can is made of steel with only a thin coating of tin. Sometimes this
coating is replaced by a lacquer. Tin protects the steel from reaction with
many food materials to a great extent. Tinplate is made by rolling mild or
low-carbon steel into sheets of strips and coating both faces with commer¬
cially pure tin either by dipping in molten metal or by electrodeposition. The
thickness of the tin coating is usually less than 0.0025 mm.

Electrolytic tinning
In this method of tinning, the base is steel. Tinplate is made by a con¬
tinuous strip which passes in 1 continuous strand through all the operations
of the tinning process. Three general types of electrolytic tinplate lines used
nowadays are acid sulfate line, halogen line and alkaline line. Acid sulfate
line was specially designed for high-speed production of heavy coating weight
and differentially coated electrolytic tinplate.

Steel base
The base steel or strip for tinplate is principally made from open-hearth
steels of different compositions designated as Type L, Type MR and Type MC
steel. Steel Type L is a cold-reduced open-hearth steel with a specified very
low content of copper and other residual impurity elements, and is used for
improving internal corrosion resistance for certain food-product containers.
The gauges used in the base steel for containers are generally in the
range of 0.125 mm to 0.3 mm.

Tin coating
Tinplate is a steel sheet coated with a thin layer of tin by various types
of coating methods, either hot-dipped, or electrolytic, or differential electro¬
lytic. Differential coated tin plate is electrolytic tinplate with a different weight
of tin coating on each surface. However, the structure of these 3 types of tin-

431
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

coating plate is basically the same. The tin plate coating consists of 4 com¬
ponents. Different foods are packed in tin cans made of specific steels. Steels
differ in their contents of trace elements other than iron. The foods for this
purpose are classified as (i) more strongly corrosive (apple juice, pickles,
cherries); (zi) moderately corrosive (figs, apricots, grape fruit); (zzz) mildly cor¬
rosive (meat, fish, corn); and (iv) non-corrosive (dehydrated soups, shorten¬
ing, frozen foods). The strength of the steel plate is important in cases of
large size can, and where pressure stresses of retorting, vaccum canning
are provided. Steel as a base material for cans is superior to aluminium in a
number of ways, for example aluminium does not have rigidity and it is
difficult to solder.

Glass
Glass is believed to be an off-shoot of pottery. Glass making was an
important industry in Egypt. The art of pressing glass in moulds to produce
bowls and cups dates to 1200 bc. Clear transparent glass was discovered at
about the beginning of the Christian Era. The 19th Century brought the
price of bottles to a more reasonable level. Glass bottles as packaging mate¬
rial have an advantage because they are chemically inert. The limitations
are they are susceptible to breakage as a result of internal pressure, impact
or thermal shocks. Besides, there is usual problems of corrosion and reac¬
tivity of metal closures. The breakage properties of glass containers can be
minimized by proper manufacturing technique for glass, proper choice of
container thickness and coating treatments. The heavier a jar for a given
volume capacity, the less likely it is to break from internal pressure. But the
heavier jar the more susceptible it is to both thermal shock and impact
breakage. Coating of various types can markedly reduce breakage of glass
containers. Coatings of special waxes and silicons impart lubricity to the
outside of glass which will help in reducing impact breakage in high-speed
filling lines. Thermal shocks can be reduced by minimizing temperature
differences between inside and outside of glass containers during filling
operations and placement under refrigeraton.

Plastics and films

Among the more important plastics and films of food packaging are
cellophanes, resins of polysters and polyethylene. The quality factors for
plastics are tensile strength, elongation, tearing strength, bursting strength
and folding endurance. The plastics and films differ in their relative strength
and weaknesses for specific food application. These packaging materials are
generally good against strong acids, strong alkalies, grease and oils, and
water. Resistance to organic solvents is variable but generally poor. They
have the advantage of light weight, inertness, cheap and resistance to break¬
age. When they are shattered, they break into a few irregular pieces which
are not likely to cut. In view of many advantages, plastic containers are

432
 PACKAGING MATERIAL

becoming more and more popular. They are used for packing different food
commodities commercially and also storing them in households. Against
these advantages, there is question of safety of some of the plastics. Exam¬
ples are polyvinyl chloride and acrylonitrile bottles for use in case of alco¬
holic beverages and soda (Corlin et al, 1990).
As time goes on, more and more new plastics are being commercialized.
Current trends are not only adding new family such as ionomers and
polyamides, but also second generation blends and combinations such as
PVDC-coated polyester, polyethylene-coated polynide, rubber modified poly¬
styrene, ethylene-vinyl-acetate-copolymers and the new coextruded films
such as polyethylene-polypropylene - polyethylene.

Papers
They are used as primary containers. Paper and papyrus were developed
originally as writing materials to replace parchment (animal skin) and vellum
(skins of new born calves or lambs). The first paper making machinery, in
which fibres were laid down on a moving wire cloth, began production in
1799 in England. The use of wood pulp in paper making was introduced in
1867. Corrugated paper was invented in the mid 1800 and shipping car¬
tons, made from faced corrugated paper board, began to replace wooden
gates and boxes about the turn of the century. They are generally treated,
coated or laminated to improve their packaging properties. Coating or im¬
pregnation is done with such materials as waxes, resins, lacquers, plastics.
Some papers are made highly porous to be absorbent for handling meat and
poultry. Kraft paper is used for bags and for wrapping and not as a primary
container. In all paper-packaging material, chemical purity and non-toxic¬
ity of its coatings are important. In addition, the microbiological condition of
paper products is also important (Harris and Loescke, 1960).

Laminations
Flexible packages are not in general hermetic in nature, although they
are excellent barriers against micro-organisms and dirt. Various flexible
materials such as papers, plastic films and thin metal foils have different
properties for water vapour transmission, oxygen permeability, light trans¬
mission, burst strength, pin hole and crease hole sensibility etc. Therefore
multilayers or laminates of these materials which combine the best features
of each are used. There are commercial laminates containing different weight
layers. They are commonly custom-designed for a particular product.
Examples of very sensitive product are instant tea mix, instant coffee powder.

MODERN PACKAGING MATERIALS AND FORMS

Glass containers
Glass containers are one of the staewarts of food packaging. Glass con¬
tainers include the following.

433
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Bottles: The bottle is the most extensively used glass container. They
may be of many different shapes but the neck is always round and much
narrower than the body.
Jars: The jar is really a very wide-mouthed bottle having no appreciable
neck.
Tumblers: These are like jars but they are open-ended.
Jugs: These are large-sized bottles with carrying handles.
Carboys: These are very heavy shipping containers shaped like a short
necked bottle and having a capacity of 13.7 litres or more.
Vials and ampules: These are small glass containers. The latter are princi¬
pally used for pharmaceuticals.

Metal cans
Traditionally cans have been made from soldered tin plate steel, but
more recently aluminium cans have been introduced. Today there are sev¬
eral more choices available, i.e. standard tin plate, light-weight tin plate,
double reduced tin plate, tin-free steel (coated), vaccum-deposited aluminium
on steel and aluminium.

Composite containers
A composite container is a container made from two or more constitu¬
ent materials. It usually consists of a paper board with metal or plastic
ends.

Aerosol containers
Aerosol containers are used to dispense a product by means of a pres¬
surized gas or liquid. That is held in the same container.

Rigid plastic packages

A wide variety of rigid plastics can be used in the forms of thermoformed,
injection-moulded and blow-moulded containers. The plastics used for
thermoformed trays are polycarbonate, polyethylene (high density), polyvi¬
nyl chloride, polyester, polystyrene and polypropylene. Most widely used
plastics injection moulded containers are polystyrene, polypropylene and
acrylonitrile. Blow moulded bottles are made of polyethylene, PVC, polysty¬
rene, and more recently polyesters (PET) shallow trays made from polysulfone
are being introduced for packaging of frozen food to be retreated in conven¬
tional and microwave ovens.

Solid and corrugated board container

Solid and corrugated fibre board materials are used to fabricate shipping
cartons and cars used extensively in wholesale and industrial shipping.
Corrugated containers are now available with easy open tier strips, self¬
locking assembling and smooth white liners permitting flexographic printing
on the exterior.

434
 PACKAGING MATERIAL

Wooden boxes and crates

Boxes are usually solidly walled, rectangular-shaped and will vary in
construction and in number of extra crates and braces used as is required
by the load. Crates are similar to boxes but may be of lighter weight and
more open construction.

Semi-rigid packaging materials and package forms

Aluminium containers, set up paper-board boxes, folding paper board
cartons and moulded pulp containers belong to this category.

Flexible packaging materials

Flexible packages are made from combinations of flexible materials.
These include basic substrate, laminating adhesives, protective or decorative
coatings and decorative inks.

Paper
Paper remains an important factor in flexible packaging because it con¬
tributes strength, stiffness, smoothness and low cost. In flexible packaging,
the basic paper used comprises bond tissue, litho, kraft, glassine parchment
and grease proof.

Films
A film is a thin flexible plastic sheeting having a thickness of 9.0254 cm
or less. The first commercial flexible film was cellophane. Cellophane is
manufactured from highly purified cellulose derived from bleached sulfite
pulp. Most cellophanes are used in packaging baked goods, confectionery,
meats and overwraps. Polymer-coated (Saran) varieties are useful for oily
and greasy products. Polyethylene is the largest volume single film used in
the flexible packaging industry.

Amylase film
Sold by American Maize Products as “Ediflex” film. It is made from corn
starch. Its most unique property is that it is edible. Possible uses for amylose
films include an inner wrapper for frozen foods where the film would dissolve
during thawing. Other possibilities are its use in portion packs, dehydrated
soups and other foods that are dissolved in water.

Ionomers
It is a new family of thermoplastics and introduced as surlyn A which is
being used as the inner component of a tetra pack container.

Aluminium foil
Aluminium foil is available in different temerpatures and alloys. Flexible
package forms are wrappers, preformed bags or envelops, pouches (Form-
Fill-Seal) and collapsible tubes.

435
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

REFERENCES

Corlin, F., Naguyen, C., Hilbat, G. and Ethanbroy, Y. 1990. Modified atmospheric packaging
of fresh ready-to-use grated conets in polymeric Fulus. Journal of Food Science 55: 4-6.
Heiss, R. and Erchner, K. 1971. Moisture content and shelf life. Pd.rf. 46(5): 53-56, 65.
Preston, L 1967. Flexible packaging. III. Cured meats. Food Package Design Technol. January
14-17.
Robertson, G.L. 1993. Food Packaging: Principles and Practices. Mercel Dekker, New York.
SaCharaw, S.S. 1980. Food Packaging. A Guide for the Supplier, Processor, Distributor. AVI
Pub. Co., West Port, Connecticut.
Taylor, M. H. 1966. Evaluated package of fresh broiler chicken. Poultry Science 45(6):
1,207-1,211.
Upadhyay, R.K., Thangaraj, M. and Jaiswal, P.K. 1994 Storage studies on sugi in different
packages. Journal of Food Science 31(1-6): 494-96.

LEARNER’S EXERCISE

1. Write a note on the different types of containers and storage structures, available for
extending shelf life of different foods.
2. Write about importance of labelling of processed foods.
3. Discuss about various packing materials used in general.
4. Write the advantages of glass and polyethylene containers for storage.
5. Explain the suitability of container for packing.

436
 Packages of
radiation stabilized foods

T he ability of ionizing radiations to kill living entities has application in

the field of food and drink disinfection. Amoebic cysts resistant to chlo¬
rination treatments, are relatively not resistant to gamma radiation. The
parasites which infect man’s food are within control with the application of
radiation treatments. Included would be the parasites of animals transmit¬
ted to man, including trichina. The low radiation resistances of insects is
noteworthy.
One of the important considerations in radiation preservation of foods
is packaging. If permanent preservation is to occur, food must be protected
from recontamination. Therefore, hermetically sealed containers are required
for sterile products. Pasteurized products require special packaging, related
to each product specifically (Desrosier and Rosenstock, 1960).

RIGID CONTAINERS

Metal rigid containers such as tin and aluminum cans have been highly
perfected. Tin-coated containers have been used successfully for more than
a century for sterile foods. The aluminium container has become more widely
used in Europe than in the United States and such containers are continu¬
ing to be perfected.

Base metal
At sterilizing dose levels, steel is stable. At dose ranging from 60,0000,000
rads and higher, damage occurs in steel. The effect on aluminum is similar.

Can coating
Radiation has no influence in promoting tin rot or tin disease and on
the transition of rhombic to cubic crystalline structure of tin. Trace amounts
of bismuth prevent this transition, in any event. Tin coatings over base steel
are suitable for food irradiation.

Sealing compounds
End-sealing compounds generally used in metal containers, are actually
improved slightly by irradiation. The exceptions are found in butyl rubber
sealing compounds which are apparently depolymerized by irradiation.

437
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Enamels
Of the interior can enamels for tin-plated cans, the oleoresinous enam¬
els are unsatisfactory for high-fat foods. Oleoresinous enamels appear sat¬
isfactory for enzyme-inactivated foods.

Container shape
Container shape is important. Ideally cubic forms are desired for best
radiation source utilization, dose distribution and control. Cylindrical rigid
containers have widespread use in canning industry. Cylindrical cans are
therefore the most commonly available, though rectangular cans are used
for certain meat items such as luncheon meat loafs and sardines in cans.

FLEXIBLE CONTAINERS

Radiation processing of foods permits the storage of perishable commodities

of high moisture content in plastic containers at room temperature. Flexible
containers have been developed for frozen and refrigerated foods, the latter
of short duration in storage function. Economical plastic containers are being
developed and should find application in radiation sterilization and pas¬
teurization. Low level irradiation of packaged meat may improve the eco¬
nomics of food distribution. Cold storage life may be increased by a factor of
5-10.

Influence of radiation on plastic packaging

Doses near 2 million rads and less radiation have no significant effects
on physical characteristic of flexible containers. At doses over 2 million rads,
changes occur in physical properties of plastic films such as polyethlene,
nylon, vinyl, and polystyrene, but the changes are of minor consequence.
Saran, pliofilm and cellophanes are made brittle if the radiation exceeds 3
million rads.
Irradiation of most foods in plastic containers results in off-odours in
the food. Nylon is very low in odour formation during sterilizing irradiation.
Polyethylene irradiation at sterilizing doses evolves objectionable odorous
compounds and short fragmentations of polymers which are carried into
the food itself.
Thin plastic films are objectionable due to the ability of micro-organ¬
isms to penetrate through microscopic openings, caused by damage during
sealing and rough handling. This may be overcome by increasing the thick¬
ness and improving sealing techniques.
Laminated foils and plastics, and combination of the latter, are func¬
tional. Some containers, such as Scotchpak. are as durable in rough han¬
dling as metal cans and performs satisfactorily up to 6 megarads as a food
package.

438
 PACKAGES OF RADIATION STABILIZED FOODS

GENERAL METHODS FOR ESTABLISHING RADIATION

STABILIZATION

Food may be stabilized by inactivating micro-organisms and enzymes present,

and protecting the stabilized food from recontamination and access to
oxygen.The latter problem is controlled by suitable packaging. The irradiation
of a food can destroy micro-organisms and enzymes. It is more efficient to
employ ionizing radiations to kill micro-organisms (Fig.71) than enzymes. It
may be desirable to inactivate enzymes by other means, in complement to
the irradiation action.

RADS x 10
Dm value for Cl. botulinum

Fig. 71. Unit of destruction of micro-organisms

Radiation
Preservation of food by ionizing radiations is a recently developed method
but has not yet gained general acceptance. As is well known, the electro¬
magnetic radiations suppress the growth of most of micro-organisms. The
posibilities of employing nuclear radiation to sterilize food have been exten¬
sively studied since the World War II. The harmful effects on the human
body from radiations from nuclear explosions have given rise to suspicion in
the minds of many people about the safety of the use of irradiated foods.
Though much work has been done on the safety and wholesomeness of
irradiated products, more careful investigations are required before allowing
the irradiated food to be used on a large scale.

439
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Kinds of ionizing radiations

There are several kinds of radiant energies emitted from different sources
which differ in wavelength, frequency, penetrating power and they have
varied effects upon biological systems. Irradiation of foods is carried out by
exposing them to high-energy radiation which penetrates them and bring
about changes within them. The principle radiations used in food irradia¬
tion are gamma-rays (wavelengths <2°A) emitted from excited radioactive
elements (60Co) and accelerated negatively charged particles, electrons (P-
particles), which are emitted from a hot cathode. Gamma-rays are very similar
to X-rays, except that they have much greater penetrating power. An elec¬
tron beam can be accelerated to very high speed and increased energies, so
that it can penetrate foods, by passing it through electronic devices.
Ultraviolet radiations are also used in preservation, but they have a
very low degree of penetration and are employed to inactivate micro-organ¬
isms on surface of food and to treat air, water and surface of food-process¬
ing equipment to reduce the number of micro-organisms.
Measurement of radiation: Ionizing radiations are measured in terms of
rads (and kilorad or megarad). A rad is 10 pJ of energy absorbed by 1 g
material. The radiation effects are related to dose by the relation.
n, n0exp (—D/D0)
where n is number of live organisms following irradiation; no, initial
number of organisms; D, dose radiation received (rads), and Do, a constant
depending on the type of organism and environmental factors.
Different organisms are sensitive to irradiation to different extent as
indicated below:
103*4 — 107 rads — micro-organisms are killed
103 — 106 rads — insects are killed
103 — 104 rads — sprouting of potato, onion, carrot, etc. are inhibited
102 — 103 rads — dose is lethal for humans

In the case of micro-organisms, the approximate sterilizing dose is 3.0 *

106 rads for bacterial endospores and 5.0 * 104 rads for yeast and fungi.
There are, however, some micro-organisms with exceptional resistance to
irradiations; for example, Micrococcus radiodurans is resistant up to 55 times
greater dosage than gram-negative organisms like Escherichia coli
(Shakunthala and Shadaksharaswamy, 1995).

Mode of action of radiations

When gamma rays and electron beam pass through foods, there are
collisions between ionizing radiations and food particles at the atomic and
molecular levels, resulting in production of ion pairs and free radicals. The
reactions of these products among themselves and with other molecules
result in physical and chemical phenomena inactivating micro-organisms
in foods. Thus, radiation of foods can be considered to be a means of achiev-

440
 PACKAGES OF RADIATION STABILIZED FOODS

ing cold sterilization of food—a food is freed of micro-organisms without the

need for high temperature.
Water is a ubiquitous ingredient in foods. Of all the reactions brought
about by ionizing radiations, the one with water is the most important in
producing foods free of spoilage micro-organisms, and of pathogens con¬
taining a greatly diminished content of spoilage organisms. Ionizing radiations
split water to produce hydrated electrons (e~); highly reactive hydrogen (H.)
and hydroxyl (.OH) radicals, excited water (H20) and ionized water mol¬
ecules (H20)+. Interactions between these products, or these products and
other components of food containing oxygen result in the formation of highly
reactive species such as hydrogen peroxide.
Hydrogen peroxide is a strong oxidizing agent and a toxicant to micro¬
organisms.
Use of radiations: Ionizing radiations may be used for sterilization of foods
in hermetically sealed packs, reduction in size of the spoilage flora on per¬
ishable foods, elimination of pathogens in foods, control of infestation in
stored cereals, prevention of sprouting of potato, onion, etc. and retardation
in development of pickled mushroom. The destruction of the growing point
causing tissue darkening of the sprouting areas of vegetables such as po¬
tato by radiations, eliminates the risk of sprouting during storage.
Irradiation does not very much affect nutritional properties of foods.
The destruction of various amounts of nutrients is of the same degree as in
heat processing. Ionizing radiations can also hydrolyze and modify proteins,
starch and cellulose.Thus, irradiation can help improve nutritive value of
certain plant materials. Significant levels of toxic or carcinogenic substances
are not produced in foods irradiated with sufficient doses of radiations. At
appropriate dose of radiations, sterilized or pasteurized foods are safe from
microbial standpoint.
Irradiation of food can also result in certain undesirable effects. Ioniz¬
ing radiation, in excessive doses, can alter the structure of organic and
biochemical compounds in food resulting in food damage. Degradation of
carbohydrates may result in loss of texture and colour. Protein degradation
results in undersirable changes in colour and odour and brings about lique¬
faction of egg-white proteins, and on irradiation it becomes thin and watery.
Irradiation of fats results in development of off-flavour and off-odour and
the loss of the natural antioxidants. Foods irradiated with higher doses of
radiation than recommended ones might themselves become radioactive
and prove harmful when consumed (Shakunthala and Shadaksharaswamy,
1995).
In the irradiation of foods for preservation, the control of the radiation
process in very necessary. The radiation dose must be carefully controlled
to destroy micro-organisms and inactivate many food enzymes. It should be
sufficient to destroy the pathogenic and spoilage causing organisms. Apart
from the intensity of radiation, amount of radiation absorbed and length of

441
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

time of radiation are to be controlled.The longer the food is in the radiation

path, the more it will absorb. Radiation energy must be provided in such a
manner that it reaches every particle of food to ensure adequate killing of all
micro-organisms.
As already stated, the use of ionizing radiations for food preservation
has been adopted very slowly. This is largely due to the unacceptable fla¬
vour of the some foods irradiated to sterilization stage. Also, the fear that
radioactivity might be induced in a food has come in the way of its extended
use. However, recent reappraisal by the WHO and the International Atomic
Energy Authority (IAEA) has resulted in the recommendation that irradation
dose up to 1 M rad is not hazardous.
Ionizing radiation emitted by radioactive isotopes (for example, gamma-
rays from cobalt 60) or generated by electrical machines producing electron
beams or X-rays are absorbed by all forms of matter. Their energy appears
as chemical change and, to a lesser extent, as heat. Living cells are particu¬
larly sensitive to these kinds of irradiation which can, therefore, be used to
kill micro-organisms, to damage the reproductive mechanism of insects,
their eggs and larvae, and to destroy actively growing cells such as those in
the sprouts of potato or the hearts of onion. Unfortunately, the use of radio¬
activity to sterilize foodstuffs possesses 2 awkward drawbacks (Magnay Pyke,
1981).
(i) Too large a dose has a harmful effect on quality: butter is bleached;
salmon loses its red colour; meat becomes darker; and a burnt off-
flavour, which occurs in high-protein foods has been vividly de¬
scribed as Vet-dog odour’.
(ii) It demands a very heavy capital investment if it is to be applied to
bulk quantities of food.
The process has, however, possibilities for development in the future
and is therefore worth consideration. The unit of absorbed irradiation is a
rad, which is equivalent to the absorption of 100 ergs/g the absorbing sub¬
stance.
The following are some of the processes so far explored:
Complete sterilization: Absolute sterility in a foodstuff requires the use
of 10 million rads (10 M rad). This damages the quality and flavour so seri¬
ously that the food becomes uneatable.
Cold sterilization: A dose of 3-5 M rad will kill most types of harmful
bacteria and give a level of sterility that is obtained in normal canning proc¬
esses. However, even this level causes unacceptable harm to flavour and
quality. Some improvement has been achieved by partially cooking the food
before it is irradiated or by keeping it well below freezing point during irra¬
diation.
Treatment of spices, etc.: The use of what are still rather high levels of
irradiation, from 1 to 3 M rad, has been applied in the treatment of spices
and seeds, which may be quite heavily contaminated with micro-organisms.

442
 PACKAGES OF RADIATION STABILIZED FOODS

This level of treatment has also been suggested as a means of reducing the
bacterial content of sugar which is to be used for canning.
Radiation pasteurization: By irradiating frozen whole egg with 0.1-1.0 M
rad, it is possible to destroy certain pathological micro-organisms, and par¬
ticularly the salmonellae that cause food poisoning, without having to thaw
the egg and pasteurize it by heat. The same treatment can be applied to
meat. The process has also been suggested for desiccated coconuts which
have sometimes been found to be a source of infection. This level of treat¬
ment has been found to increase the storage life of products such as sau¬
sages and fish. Its main drawback is that it is difficult to avoid the development
of ‘irradiation flavour’. Radiation pasteurization cannot be used for fruits or
vegetables because it appears to damage the cells and, while inhibiting cer¬
tain bacteria, causes the tissues of the plant to break down.
Disinfestation: The irradiation with 0.02 M rad of foodstuffs such as
grain or dried fruits while they are being unloaded from ships or handled in
bulk stores destorys insect eggs and make the insects incapable of breed¬
ing. For the process to be effective, a thin layer of the foodstuff must be
exposed to the radioactivity and consequently the capital cost of an installa¬
tion sufficiently large to deal with materials in bulk is very high.
Sprout inhibition: Of all living cells, those that are actively growing are
most susceptible to radiation. It has consequently been found that quite
small doses of about 0.01 M rad will destroy the cells which grow into sprouts
from the eyes of potatoes without affecting the other cells of the plant.
The use of radioactivity in food technology is still in the stage of develop¬
ment. While certain promising applications have been found, it has yet to be
established whether these possess advantages over those of more conven¬
tional methods, sufficient to justify the cost of the necessaiy installation. At
all the levels of irradiation described above, there is no chance of any harm¬
ful degree of radioactivity being transferred to foods under treatment.

REFERENCES

Desrosier, N. W. and Rosenstock, H.M. 1960. Radiation Technology in Food, Agriculture and
Biology. AVI Publishing Co., West Port, Connecticut.
Magnas Pyke. 1981. Food Science and Technology, edn 4. John Murray, London.
Shakunthala, M.N. and Shadaksharaswamy, M. 1995. Foods: Facts and Principles. New Age
International (P) Ltd, Publishers, New Delhi.

LEARNER’S EXERCISE

1. What do you mean by flexible containers?

2. What are the various general methods for establishing radiation stabilization?
3. Write about kinds of ionizing radiation.
4. Enumerate in detail the various uses of radiation.

443
36 Packages of
dehydrated products

ORIENTATION

P lastic materials are oriented, i.e. stretched and heat-set under control
led conductors, to improve their strength, barrier and other properties.
Plastics oriented in 1 direction only (machine direction -MD) will have high
tensile strength and are used as filaments, yarns and straps. Bi-axial orien¬
tation results in improvement of some physical strength properties such as
tensile, impact, low temperture resistance and increased barrier properties
to the passage of water vapour, gas and volatiles. However, effective elonga¬
tion and tear strengths decrease due to orientation. Commonly, plastics
such as PET, nylons, and polypropylene lend themselves well for orienta¬
tion process (Sacherow and Griffin, 1970).

METALLIZATION ,
Vaccum metallization of aluminium on plastic films especially after seventies
has been carried out to improve the barrier properties rather than attrac¬
tiveness. Though PET, nylons and polypropylene are best suited for
metallization, other substrates can also be used for this purpose. The ad¬
vantages claimed for metallization over the use of aluminum foil web are
greater resistance to flexing and creasing and lesser susceptibility to me¬
chanical damage. An outer plastic film such as those of polypropylene and
polyethylene greatly enhances the utility of metallized films.

CO-EXTRUSION OF MULTILAYER FILMS

By this process, a composite packaging material consisting of two or more

individual functional webs are made as opposed to coating or laminating.
Through judicious choice, it is possible to develop an optimum system with
minimum cost, although the initial investments are heavy for this process.
In coextruded structures, generally the inner skin layer provides sealing
and chemical resistance properties, while the inner tie layers provide ad¬
herence and barrier functions. The outer layers contribute thermal integrity,
scuff resistance, stiffness and printability. Currently coextruded films are
widely used for the packaging of liquid foods such as oils and fats, and

444
 PACKAGES OF DEHYDRATED PRODUCTS

many dry foodstuffs. High density polyethylene (HDP), low density

polyethylene(LDPE), HDPE/ethylene-vinyl alcohol (EVA), HD PE/Nylon/EVA,
LDPE/polyvinyl dichloride (PVDC)/LDPE, Nylon/ lonomer etc are the com¬
mon coextruded structures used for food packaging (Heiss, 1970; Kumar,
1989).

STRETCH BLOW-MOULDING

This process of making rigid containers uses biorientation phenomenon

during blow moulding of plastics. Advantages conferred by stretch blow
moulding are improved barrier properties, resistance to creep, stress crack
resistance, impact resistance and transparency. Currently, technology is
available for manufacturing stretch blow containers made of polyethylene
tetraphthalate (PET), polyvinyl chloride (PVC), and polypropylene polyethylene
(PP).

THERMOFORM FILL SEALING

In this process, a container made of two webs, the lower one formed into a
cup shape is Filled with the food product while the upper web becomes the
lid closure, which is hermetically sealed. Frozen foods, single dose use food
containers, vacuum or controlled atmosphere packages etc. are made by
this process.

PACKAGE FORMS AND TECHNIQUES

Aseptic packaging
This connotes the packaging of sterilized shelf-stable food in pre-steri-
lized packages. This system comprises flexible pouches, semi-rigid and rigid
containers and bag-in-box systems. Liquipak table-top cartons are made of
paper-board laminated to foil and polypropylene polyethylene or EVA. The
brik pack (rectangular) and tetrahedral packages are usually made of
polypropylene polyethylene/paper/polypropylene polyethylene, paper/foil/
polypropylene polyethylene or polythropylene with loose liners of low den¬
sity polyethylene or LDPE, used for greater mechanical strength. Semirigid
portion packs made by thermoform fill seal type consists of polystyrene (PS)
or polyvinyl chloride (PVC) base with plastic laminated closures. Bag-in-box
systems consist of metallized PET nylon, PE and such laminates. These
bags typically range in size from 3.7 to 1,135 litres (Anon., 1971).

Retortable containers
Retortable containers, which are attractive to metal and glass containers,

445
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

have been in development for many years, but only recently have become
common due to developments in superior barrier properties, seal integrity,
ability to withstand thermal processing, mechanical strength etc. Such typical
structures consist of an outer PET or nylon layer, middle foil and inner cast
polypropylene (CPP) layer to provide the required functional properties. For
short-term storage and for foods with less stringent packaging requirements,
transparent pouches made for polyvenyl dichloride (PVDC)-coated nylon of
PET with ethylene vinyl alcohol (EVOH) and CPP are used. A novel sterilizable
‘plastican’ is a container co-injection moulded with polypropylene skin lay¬
ers and EVOH middle layer to provide oxygen impermeability. It is claimed
that these cans can be filled and retorted at 130°C on the same lines and at
comparable rates as metal cans (Kumar, 1989).

Modified and controlled atmosphere packaging

To extend the shelf-life of highly perishable foodstuffs such as fresh
produce, meats and fish, the ambient gas concentrations inside the sealed
plastic bags need to be controlled. Many olefmic plastics, plasticized polyvinyl
chloride, and PVDC coated plastics are responsible for the growth of this
system of packaging. Most controlled atmosphere packaging systems of fresh
and pre-cooked foods are carried out in thermoform-fill-seal machines using
PS/EVOH/PE for the base sheet and PVE/PVDC/PE for closures.

Skin, shrink and cling film packaging

Skin packaging is a vaccum-forming process in which plastic film is
moulded on the food product such as fruits, vegetables and fish, placed in a
tray. Materials based on low density polyethylene, polyvinyl chloride, lonomer,
EVA are being increasingly used to pack such products. Another technique
of wrapping goods in plastic films is shrink wrapping which produces a tight
wrap even on oddly-contoured food articles. Applications of shrink wrapping
include dressed poultry, overwrapping of cans, bottles and cartons and even
whole pallet loads. LDPE is the least expensive, but polyvinyl chloride and
other plastics are used when greater strength and adhesion are required. A
polypropylene polyethylene cling film has been assessed for wrapping fresh
produce to reduce transpirational loss and for extending shelf-life.

Micro-ovenable containers
Conventional aluminium trays cannot be used in microwave ovens and
hence there is a need for such trays which are also capable of reheating in
a conventional oven. Such dual ovenable features coupled with freezer stor¬
age have been achieved by PET-coated board, thermoformed PET trays, crys¬
tallized PET, PC and very recently polyetherimide containers.

Other package forms and components of plastics

Although not specific to food packaging, plastics are used in a wide
variety of packaging applications including foam mouldings made of

446
 PACKAGES OF DEHYDRATED PRODUCTS

expanded plastics such as polystyrene, polyurethane, polypropylene polyethy¬

lene and styrene copolymers. They are used as cushioning materials, insu¬
lated boxes and partition trays etc. Recently, methods have been devised to
form corrugated plastic sheets made of polypropylene, its copolymers and
high density polyethylene plastics. They are claimed to possess high me¬
chanical strength even under high humidity and other advantages. Further,
plastics have come to be increasingly used in applications hitherto held by
other traditional materials, for example crates, sacks, drums and jerry cans,
pallets, straps twine etc.
In future new areas of development in plastic food packaging field which
could be envisaged are: improvement and development in existing and newer
grades of plastics to improve protective properties, new functional multi¬
layered structures, improved thermal stability, pest-resistant materials and
new fabrication and conversion techniques. Anyhow, the major accent will
be on reduction in costs with better functional qualities.
Packaging will eliminate industrial wastage and increase the market for
Indian products both in India and abroad. Let us recapitulate the need for
packaging with particular reference to the context of fruits and vegetables
packaging industry in this country over the years. India has contributed in
different areas: cost has been reduced particularly on tin-plate, cans; thick¬
ness of tinplate has been reduced; the amount of tin coating that has been
put on it has been reduced; for non-processed food items, to a large extent,
tinplate has been replaced by black plate; in terms of solder that is used, we
now use low-tin solder as opposed to the relatively high-tin solder that was
used earlier. In terms of product development, the packaging industry has
introduced,for example, refill cartons, flexible sachets,composites, and more
recently beverage cans, i.e. beer cans. Despite all these innovations, the
packaging industry has not been able to catalyse and the reasons are:
First, there is lack of growth in the market of its end-use product.There
is low purchasing power, and the discretionary expenditure is extremely
limited. There is of course the high cost of the product, due mainly to highly
physical levies and very importantly to a low volume of production. Besides
this, we have other social factors, basically habits of eating, illiteracy, lack
of health consciousness, and so on. We also have a major problem in terms
of transport of food, lack of communication and storage facilities, and un¬
economic operations.
Packing industry has to accelerate its cost reduction and production
development programmes. It should provide further support services, in¬
cluding advisory services, designing, and machinery building. Finally we do
have bottlenecks in terms of raw materials, not just on tinplate but on many
polymeric materials like polyester films, metallized polyester, polyvinyl chlo¬
ride etc; these must be made available at a reasonable rate, so that these
packaging materials can be used to the advantage of consumer and to suit
their speific requirement.

447
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Between 1976 and 1981, only laminates and plastics have shown any
growth over the last few years. All the others, glass, paper, paper board,metal
and wood showed declined growth. Paper and board have about a 45% share
of the market at the present moment.
There are 2 main types of development in plastics, i.e. rigid and flexible.
The most interesting developments in rigid plastics have been the use of
polyethylene terephthalate (PETP) in the manufacture of bottles for carbon¬
ated soft drinks. Co-extruded laminates are used for bottles. The PETP bot¬
tles are stretch blow-moulded, and are strong enough to resist the pressures
generated normally inside carbonated beverages (50-60).
Many people have developed strapping materials. One is from jute, us¬
ing which twine can be made.Similar materials are twisted from rayon string
and paper string. The tribal people use a type of strap material, which is the
stalk of a long creeper that can be split into a long strip.
Bomboo baskets are used in very large quantity, but in general the
strength is very poor. The strength could be improved twice by simply in¬
creasing the thickness of the vertical column, without any extra labour be¬
ing required. The square box is another article wherein a lot of space in the
stacking condition can be reduced if aeration is not particularly needed.
A traditional corrugated fibre-board box is used for the packaging of
banana for export. For Indian conditions, these have to be stitched in the
field, and during transport in trucks, one will have to carry a lot of empty
space. Also, as Indian labourer normally carries a load on his head or shoul¬
der, and the package suits this well.
For this purpose, collapsable boxes are now available. These require
smaller amounts of material, and the box is quite suitable for Indian condi¬
tions. However, it is not acceptable to foreign buyers who say that the flaps
will interfere in super market sales, so a tear-off top is developed to over¬
come this difficulty. One important new development taking place in Eng¬
land in flexible packaging is wrapping of products such as meat, poultry,
fruits and vegetales in film for chilled storage and distribution, at a tem¬
perature of about 4°C. Here gases are injected inside the film which will
delay post-harvest changes, delay ripening of fruits and enhance red colour
of meat. This technique is known as gas flushing. It will take off in the next
few years; at present it is very much in its infancy in 1 or 2 areas.
The rigid form/fill/seal packs have seen quite a degree of evolution.
One of the easiest forms is tetrapak which is composed of heavy weight
paper-board/aluminium/ polyethylene material, and this has been used
very successfully for milk, milk products and fruit juices. The original shape
did give rise to problems of handling and stacking, and now it has been
largely superseded by tetrabrik which is shapped like a brick and has been
used in England for packaging fruit juices. A newer development has been
tetrakind, a D-shaped cylinder formed from 2 webs of polystyrene. These
various tetra systems are used for aseptic filling. Sterilization is carried out

448
 PACKAGES OF DEHYDRATED PRODUCTS

by means of either hydrogenperoxide, or ultraviolet irradiation, or gamma

radiation from a cobalt 60 source.
Thermally processed products are at present usually being packed in
cans. Fruit juices, jams, jellies, alcoholic beverages, etc. are commercially
packed in glass bottles, but there are problems of excessive breakages, ex¬
cessive weight and high transportation costs.
In dehydrated foods, 2 major reactions limit shelf-life. The first is the
Maillard reactions, on the interactions between sugar and amino acids or
proteins. The second factor is oxidation reactions, which are mainly respon¬
sible for rancidity development and decolourization of carotenoid and
anthocyanin pigments.
In thermally-processed ready-to-eat food products like halwa, kheer,
and meat and vegetable curries, use of flexible packages instead of rigid
cans has mainly been based on a laminote which is a nylon/aluminium
foil/copolymer of polypropylene and polyethylene. Unfortunately this mate¬
rial remains to be produced in the countiy, and so an indigenous material
produced in sufficient quantity, viz. polypropylene polyethylene (PP) film
produced by the IPCL, Baroda, is being used.

REFERENCES

Anon. 1971. Canwood fruit pack. Canner/pectin 1971-72. YearBook 140, No.9, 82.
Heiss, R. (Ed.). 1970. Principles of Food Packaging. Food and Agriculture Organization of the
United Nations, Rome.
Kumar, K.R. 1989. Recent developments in plastics for food packaging. (In) Proceedings of the
Second International Food Convention, held at Mysore, pp. 702-706.
Sacharow. S. and Griffin. P.C. 1970. Food Packaging. Food and Agriculture Organization AVI,
West Port, Connecticut.

LEARNER’S EXERCISE

1. Explain about co-extrusion of multilayer films.

2. What is aseptic packaging?
3. Flexible packaging is used for which foods.
4. Discuss about package forms and techniques.

449
.

*
 Index

A Black tea 225

Adsorbed solvent 21 Blanching 189
Adsorption 26 Bleaching agents 32
Adulterated food article 47 Blue cheese 83
Advantages of dried eggs 302 Blue green algae 385
Advantages of microwave cooking 371 Boiling point 7
AGMARK 61,63,66 Boundary phenomena 26
Agricultural Produce Grading and Bread improver 332
Marketing Act 56 Brown sugar 257
Agriculture Marketing Products Bureau of Indian Standards 62
and Grading Act 1973 53 Butter 174, 282
Agro-chemical residues 68 Buttermilk 281
Alcoholic beverages 232 By-products of sugarcane 264, 404
Allspice or pimenta 244 C
Alveographe curve 336
Amylase 15 Cabinet dryer 185
Angel cake 361 Cabinet drying 184
Aniseed 244 Cacao 228
Anti-vitamin factors 147 Cake 157
Antinutritional factors 145, 147 Cakes, cookies and pastries 356
Antioxidants 31 Camellia sinensis 224
Arecanut 244 Candied fruits 202
Aromatic barks 241 Canned and frozen whole milks 289
Aromatic fruits 241 Canned meat 316
Asafoetida 244 Canning 187
Aseptic packaging 445 Canning of fried chicken 318
Canning operations 192
B Caper 244
Baby care 52 Caramelization 257
Bacteria 89 Caraway 245
Baking soda 332 Carbohydrates 139,272
Bandal cheese 285 Carbonated beverages 215
Barbender amylograph 337 Cardamom 245
Beef 305 Celery 245
Beer 75, 235 Cereals 97
Beet sugar 256 Changes during egg storage 296
Betal 244 Channa 285
Beverages 73 Cheddar cheese 82
Biochemical spoilage 90 Cheese 79,283
Biological effects 70 Chemical composition of coffee 221
Biological value 399 Chemical spoilage 92
Biscuits, breads and rolls 349 Chiang 416
Bishop’s weed 244 Chicory 224

451
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Chiffon cakes 361 Confectionery fats 261

Chillies and capsicum 245 Consistometer 43
Chillies cayenne 245 Consumer Protection Act 63
Chillies paprika or Spanish Containers 431
pimento 245 Contents of egg 300
Cichorium intybus 224 Continuous phase 19
Cinnamon bark 245 Convenience foods 125
Cinnamon leaves 245 Conventional foods 399
Citrus fruits 178 Cooking technique evolution 4
Clarification 273 Cool chambers 186
Clarification by freezing 210 Coriander leaf 246
Clarification by heating 210 Coriander seeds 246
Classes of Indian confectionery 263 Corn (maize) flakes 132
Classification of foods 1 Corn processing 130
Classification of fruits 178 Corn sheller 129
Classification of poultry 312 Corn starch and syrups 132
Clove 245 Cottage cheese 284
Cocoa 228 Cotton seed 172
Cocoa beverages 230 Cotton-seed meal 402
Cocoa butter 252 Cream cheese 284
Cocoa products 266 Cube sugar 256
Coconut 154,172 Cumin, black 246
Coconut meal 403 Cumin, white 246
Coconut seed 172 Curd 281, 291
Coffea arabica 219 Cured and smoked poultry 318
Coffea liberica 219 Cured meat 317
Coffea robusta 219 Curry leaf 246
Coffee making 222 Cutting device 43
Coffee, tea and cocoa 219 Cyanogens 147
Cold plate test 195 n
U
Colloid chemistry 19
Colloidal dispersion 19 Dairy analogues 408
Colloidal particles 19 Decca cheese 284
Colloidal system 19, 24, 26 Decortication 139
Coloured spices 241 Dehydrated foods 126
Commercialization 424 Dehydrated meat 317
Composition of khoa 285 Dehydro-freezing 187
Composition of spray-dried Dhal 143
Spirulina 386 Diamond sugar 257
Composition of tea 227 Dill 246
Compressimeter 43 Disadvantages of microwave
Concentration by freezing 201 cooking 372
Concentration ih vacuum Disinfection of grains 421
evaporators 202 Disperse phase 19
Concentration of fruit juices 201 Dispersion 24
Condensed milk 282 Dissipation 69
Condiments and spices 241 Distilled spirits 237
Confectionery and chocolate Dough-testing equipment of
products 260 dynamic type 334

452
 INDEX

Drip coffee 223 Fish liver oil 174

Drum drying 184 Flaked rice 105
Drupes 178 Flaking machine 149
Dry milk 283 Flash pasteurization 274
Duo-trio test 41 Flavour enhancers 32
E
Flavour measurements 44
Flavour profile method 42
Edible oilseed meal 401 Flavoured milk and milk drinks 290
Effect of pasteurization 273 Flavouring agents 32
Egg production 294 Flexible containers 438
Egg quality 296 Flour milling 109
Electric charge 21 Flour treatments 113
Emulsification 175, 176 Fluidity 26
Emulsifier 22,23 Foam 19, 26
Emulsifying agents 22 Foam-mat drying 185
Emulsion 19 Food acts 57
Enzymatic spoilage 90 Food additives 30, 34, 35
Enzyme inhibitors 133 Food adulterants 49
Enzymes 272 Food adulteration 46, 49
Espresso coffee 224 Food adulteration tips 51
Essential Commodities Act 56 Food analogue 406
Evaporated milk 282 Food colours 33
Evaporating cooling 186 Food evaluation 39
Export Inspection Council 63 Food irradiation product 422
Export Products Control Food labelling 46, 64
Order 1954 54 Food laws 52, 57
Extensometer 337 Food preparation 3
Extraction of oils from animal fats 173 Food quality 55
Extruded materials 163 Food science and technology 2
Extruded products 162 Food standards 46, 55, 57
Extrusion cooker 162 Food texture 43
Extrusion cooking 163 Food texturometer 338
Food enzymes 15
F
Food microbes 73
FPO labelling 65 Food spoilage 86
FAQ (Fair average quality) 62 Foods 43, 73, 126, 169,418
Farinograph 334 Forms of sugar 256
Fats 167,272 Freeze drying 187
Favism 147 Freezing point 8
Fennel 246 Frozen egg powder 300
Fennugreek 246 Fruit and vegetable juices and
Fermentation 73 drinks 207
Fermented beverages 74 Fruit cake 359
Fermented milk 291 Fruit cordial 208
Fermented products 73 Fruit juice concentrate 208
Fermented soya products 410 Fruit juice cordials 214
Finger millet 119 Fruit juices and syrups 197
Finished cheese 84 Fruit Products Order 54, 61
Fish 319 Fruit punches 208

453
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Fruit squash 208 Irradiated food 418

Fruits and vegetables 178 Irradiation 420
Irreversible colloids 24
G 63, 65
ISI mark
Garlic 246 Iso-electric points 21
Gels 25 j
Ginger 246
Ghee 282 Jaggery 252
Gioddin 292 Jelly 195
Glazed fruit 202
K
Gluten 112
Goitrogens 146 Kedale 413
Grape wine 74 Kefir 292
Green tea 226 Khandsari sugar 256
Groundnut 155 Khoa 285
Groundnut meal 172,401 Kilo Guy 421
Gur (jaggery) 255 Koikuchi-shoyu 414
Kokam 246
H
Kumiss 292
Health Ministry standards 58 T
MJ
Hedonic method 40
Hoat-air oven 345 labelling 46
Holder-process pasteurization 273 Labelling and casing 192
Homogenization 175, 274 Lactic acid fermentation 205
Huller operations 101 Lard 173
Hydrogen-ion concentration 12 Lathyrogens 147
Hydrogenation 174 Leaf protein 393
Hydrophilic colloids 24 Leaf protein concentrates 392
Hydrophobic colloids 24 Leafy vegetables 180
Leavening agents 331
I
Leben 292
Iced coffee 224 Legumes 138
Iced tea 228 Lipases 16
Icings and fillings 362 Lipids 139
Implementing agencies for food Lipoxygenase 16
standards 57 Low-sodium milk 289
Indian confectionery 263 Lye peeling 189
Indian spices 250
M
Indicators 297
Industrial by-products 150 Mace 246
Infant foods 126, 160 Maize 127,128
Insecticide removal 70 Maize products 131
Instant food mixes 125 Maize shelling 129
Instant rice 105 Malt beverages 75
Instant tea 228 Malted milk 289
Intentional food additives 30 Malting 121
International Commission for Mango, green 247
Uniform Methods of Su 56 Mango-ginger 247
International efforts 423 Manufacture of raw cane sugar 253

454
 INDEX

Marjoram 247 Nutritional value of Spirulina 388

Market standards 57 Nuts 152
Masticometer 43
O
Maturing agents 32
Matzoon 292 Objective evaluation 42
Meat analogues 408 Oil palm 153
Meat cooking 310 Oils 157,167
Meat extenders 161 Oils and fats function in food 169,170
Meat Products Statutory Order 54 Oilseeds 152,401
Mechanical spoilage 92 Olive 153
Metallization 444 Onion 247
Methods of increasing meat Oolong tea 227
tenderness 309 Oreganum 248
Methods of slaughter 307 Osmotic pressure 8
Methods of sterilization 273
P
Microbial decontamination 422
Microbial protein 397 Package forms 445
Microbiological spoilage 86 Packages of dehydrated products 444
Micronutrients 250 Packages of radiation stabilized
Microscopic view of Spirulina 387 foods 437
Microwave blanching 374 Packaging materials 429, 433
Microwave cooking 368 Paired comparison 41
Microwave cooking and nutrition 375 Panir (paneer) 284
Microwave energy and food Paprika 248
preservation 373 Paramesan cheese 83
Milk and milk products 271, 281 Parboiling 101
Milk beverages 287 Parsley 248
Milk products 281 Pasteurization 273
Milk substitutes 160 Peanut butter 176
Millets 97,118 Peanut milk 160
Milling 142 Pearl millet 118
Milling operations 110 Pectic enzymes 17
Minerals 139, 272 Peel and drawplate ovens 346
Mini rice mill 100 Penetrometer 43
Mint 247 Pepper, black 248
Miso 410 Pepper, long 248
Molasses 264 Peppermint 248
Moulds 86 Percolator coffee 223
Mushroom processing 382 Permitted food colours 34
Mushrooms 381 Pesticide contamination 69
Mustard 247 Pesticides 68
Mutton 305 Petroleum yeast 395
Mycotoxicosis 134, 135 PFA Act and Rules 48
Phenolic spices 241
il
Physical spoilage 92
Nutmeg 247 Physico-chemical properties 6
Nutrient composition of legumes 138 Phytase 16
Nutrient supplements 33 Phytohaemagglutinins 146
Nutritional importance of oils 167 Pickling 204

455
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Pickling of poultry and meat 316 Ranking 41

Plant oils 153 Rapeseed meal 403
Plant proteins 392 Ready-to-serve beverages 201
Plasticity 26,27 Refined sugar 254
Pomegranate 248 Refining 171
Popped rice 106 Refining cane sugar 254
Poppy 248 Retortable containers 445
Potentiators 32 Rheological model 44
Poultry 312 Rice 98
Powdered sugar 256 Rice bran 106
Preparation of fruit jam 193 Rice bran oil 106
Preservation methods for meat Rice milling 100
and poultry 314 Rice miso 411
Preservation of milk 275 Rice polishing 107
Preservation of shell eggs 298 Rice processing 99
Preservatives 30,31 Rigid containers 437
Prevention of Food Adulteration Ripening of fruits 421
Act 46, 54, 60 Riversible colloids 24
Process specifications 422 Rock sugar 257
Processed products 193 Rule A-07.03 Honey 63
Processing 1 Rule: A-18.06 Food grains 63
Processing of eggs 301
S
Processing of meat 316
Processing of poultry 318 Safety periods 69
Proso millet 120 Saffron 248
Proteases 16 Sage 249
Protein coagulation 27 Sauces 202
Protein denaturation 27 Sausages 317
Protein efficiency ratio 399 Scoring 42
Protein isolates 404 Seafoods 422
Proteins 27, 138 Sensory evaluation 40
Pseudo yeast 88 Sequestrants 31
Puffed rice 105 Sesame 172
Puffing 145 Sesame meal 403
Pulses 139 Shearing device 43
Pungent spices 241 Sheet or flake test 195
Sherbats 208
Q Single cell proteins 395
Quality gradation 58 Skyr 292
Quality centres 59 Slaughtering techniques 307
Quality control legislations 63 Slide-flue oven 341
Quality enforcement 50 Smoked meat 317
Quick cooking pulses 145 Soft drinks 231
Soft-curd milk 289
R
Solar dryer 185
Radiated food 418 Sols 20
Radiation stabilization 439 Soluble coffee 224
Radiations 418, 419, 439 Solutions 6
Radioactive decay 419 Sorghum 116,123

456
 INDEX

Sorghum grain 116 Sweetners 33

Sorghum papad 126 Swiss cheese 82
Sorghum semolina 124 Syneresis 25
Sorting and grading 188 Syneresis or weeping 197
Soy protein isolate 159 Syruping or brining 189
Soya sauce 203, 415 Syrups 265
Soybean 171
T
Soybean cheese 416
Soybean meal 401 Taette 292
Soybean milk 160 Tallow 173
Spearmint 249 Tamari-shoyu 415, 416
Specific gravity 10 Tamarind 249
Spices 242 Taragon or estragon 249
Spirulma production and its Tea 224
applications 387 Tempe 412
Spoilage by insects, parasites and Texture measurement 42
rodents 91 Textured vegetable protein 161, 406
Spoilage in eggs 297 Theobroma cacao 228
Sponge cake 358 Thermoform fill sealing 445
Spray dried whole egg 301 Thickeners 33
Sprout inhibition 420 Thyme 249
Spun protein analogues 161 Tolerance limit of pesticides 68
Spun vegetable protein 407 Toned milk 282
Squashes 213 Traditional eastern alcoholic
Stabilization 439 beverages 239
Stabilizers 33 Traditional milk preparations 285
Starch modifiers 32 Triangle test 41
Steam tube oven 344 Triticale 113
Steeped coffee 223 True solutions 20
Storage conditions of dairy Turmeric 249
products 277 Types of baking ovens 340
Storage of fruits and vegetables 206 Types of bread 352
Stretch blow-moulding 445 Types of fruit juices 210
Structure of microwave oven 370 Types of khoa making 285
Subjective evaluation 40 Types of meat 305
Sugar 252 Types of seafoods 319
Sugar cookery 257
U
Sugar, jaggery and cocoa butter 252
Sulphitation 254 Ultra high temperature treatment
Sun drying 184 of milk 280
Sunflower seed 173 Ultra-high-temperature (UTH)
Sunflower seed meal 403 process 274
Surface active 22 Ultra-pasteurization 276
Surface and interfacial tensions 9 Use of enzymes in milk products 280
Surface tension 26 Use of preservatives 278
Surface-acting agents 22, 32
V
Surface-ripened cheeses 83
Surti cheese 284 Vaccum metallization 444
Suspension 19,20 Vacuum coffee 223

457
 TEXTBOOK OF FOOD SCIENCE AND TECHNOLOGY

Vanilla 249 Wheat 107

Vapour pressure 7 Wheat milling 108
Vegetable Oils Control Order 54 Wheat popcorn 114
Vegetable proteins 407 Wheat-flake processing 114
Vegetables in tropics 180 White sugar 254
Vienna ovens 346 Whole maize meal 131
Vinegar 76, 77, 78 Wines 233
Viruses 89 Winterization 174
Viscometer 43 Winterizing 175
Viscosity 9, 26
Y
Vitamins 139,272
Yeasts 88, 396
W Yoghurt 291

Water-oil interface 22 Z
Wetting agents 22 Zym otachy gr aphe 336

458