Introduction to Food

Science UNIT 2 FOOD FROM PLANT SOURCES

Structure
2.0 Objectives
2.1 Introduction
2.2 Food Grains
2.3 Cereals
2.3.1 Structure and Composition of Cereals
2.3.2 Post Harvest Processing
2.3.3 Foods from Cereals
2.4 Grain Legumes
2.4.1 Composition of Legumes
2.4.2 Processing Pulses
2.5 Oilseeds: Characteristics
2.5.1 Processing of Oilseeds
2.6 Horticultural Crops: Structure and Composition
2.6.1 Post Harvest Technology
2.7 Let Us Sum Up
2.8 Key Words
2.9 Answers to Check Your Progress Exercises
2.10 Some Useful Books

2.0 OBJECTIVES
After reading this Unit, we shall be able to:
• list out foods from plant sources;
• describe the of cereals, legumes, oilseeds, and horticultural crops; and
• explain post harvest processing mainly: primary, secondary and tertiary
processing of plant sourced foods.

2.1 INTRODUCTION
We have learnt that food substances are primarily composed of carbohydrates,
fats, proteins, minerals, vitamins and water/moisture. It is consumed by the
animal or human being for nutrition and satiety. Food may be sourced from
plants, animals and other categories such as fungus. Man uses plant products
that correspond to many different parts of the plant and many different stages
in plant development as a source of food. There are around 2,000 plant species
that are cultivated for food, and many have several distinct cultivars. The
plant-sourced foods can be grouped as seeds, roots, leaves, stems, flowers and
fruits. Among these, seeds are the most important source of food because they
are enriched with all the nutrients and energy necessary for the plant's initial
growth. Seeds also account for bulk of the foods consumed by human beings.
These include cereals (e.g. rice, wheat, maize, and millets), legumes (e.g.
beans, peas, and lentils), nuts and oilseeds. Apart from seeds, other plant parts
like roots, leaves, stems, flowers and fruits are also eaten as food.
On the basis of keeping quality and suitability for storage, plant products can
be grouped into durables and perishables. Cereals, pulses and oilseeds are
mainly durables whereas fruits and vegetables are perishables. Perishables are
high in moisture content and prone to spoilage after their harvest. Whereas
cereals are low in moisture and could be stored for longer periods. The plant
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products first stored and transported by man were all durables. It is only Food from Plant
Sources
relatively recently that man has been able to keep and transport the more
perishable products. Keeping quality of perishables varies from few hours to
some weeks. The main difference between durables and perishables are
summarized in Table 2.1.

Table 2.1: Difference between durables and perishables

Durables Perishables
Designed for preservation Not designed for preservation
Low moisture content, usually High moisture content, usually
10-15% 50-90%
Small unit size Large unit size, typically 5g to 6 kg
Often symmetrical in shape Often asymmetrical in shape
Hard texture Soft texture
Stable- inherent storage life of years Perishable- natural storage life of a
few days to month depending on type
Losses mainly caused by external Losses caused by external factors,
factors, e.g. mould, insects and mainly moulds and bacteria, and
rodents internal factors, e.g. respiration,
sprouting, ripening, etc.

2.2 FOOD GRAINS

The grain seeds that are used primarily for food are referred to as food grains.
These include rice, wheat, corn (maize), coarse grains (sorghum and millet)
and legumes/pulses (beans, dried peas, and lentils). The grain seeds that have
high oil content and processed for oil extraction are called oilseeds. The grains
are compact and dry. They can be easily handled, transported and stored. They
also have good storage stability. All the grain seeds used as food are important
in meeting the basic nutritional requirement. The grains have high
carbohydrates content, sufficient protein, fats, vitamins and minerals.
Based on their main growing season in India, food grains are usually grouped
as Kharif (rainy season) crops or Rabi (winter season) crops. Kharif crops are
grown during summer and rains during April-August, and harvested by
October whereas Rabi crops are generally sown between October to February
and harvested by May. Rice, maize, millets, groundnut and soyabean are
important Kharif crops whereas wheat, barley and a variety of oil seeds are
Rabi crops. The total food grain production in India in the year 2005-2006 was
208.3 million tonnes, out of which cereals accounted for 195.2 million tonnes.
The total food grain production in 2007-08 was 227.32 million tonnes (mt).
The production values for major cereals included: rice-95.68 mt, wheat-76.78
mt and maize-18.54 mt. The production of food grains is seasonal and weather
sensitive.

2.3 CEREALS
Food grain crops that belong to the grass family (Graminae) form a major part
of the food grains basket. They yield seed grains usable as food by humans and
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 Introduction to Food livestock. The common cereals are: rice, wheat, barley, oats, maize (corn),
Science sorghum, rye, and certain millets. Jowar and Bajra are important millet crops
grown in India. There are several reasons why cereals are so important on the
human diet. They can be grown in a variety of areas, some even in adverse soil
and climatic conditions. They can be easily cultivated and give reasonably
assured high yields compared to most other crops. Cereal grains are grown in
greater quantities and provide more energy worldwide than any other type of
crops. Because of their big contribution to the dietary and nutritional
requirements, these are known as ‘staple foods’. In some developing nations,
grains constitute practically almost the entire diet of poor people.

2.3.1 Structure and Composition of Cereals

A) Structure

The structure of all cereals is similar, yet each one has its distinguishing
features. The cereal grain is a one-seeded indehiscent fruit or caryopsis. The
basic structure involves three parts--the bran (a layered protective outer coat),
endosperm (the large starchy part, containing some protein) and the germ (the
embryonic part of the plant) (Fig. 2.1).

Fig. 2.1: Structure of cereal grain

The grains also have a husk cover which surrounds the entire bran. The husk or
hull is the external, fibrous part of the grain that protects the grain during its
formation and is totally indigestible. The bran consists of several layers, the
fruit coat (pericrap) and seed coat (testa). The germ or embryo is the part of the
grain from which a new plant develops. The endosperm or starchy part
constitutes between 80 per cent and 90 per cent of the grain. It is the food store
of the grain providing nourishment for the germinating plant. It is the most
important part of the grain for the consumer and miller since it is from this part
that the flour is obtained.
Important food substances like carbohydrates, protein, fat, vitamins and
mineral matter and water/moisture are found in cereals. However, they occur in
different quantities in the different grains. Some contain large quantities of
protein while others practically have none. Certain ones have considerable fat
content while others have it only in lesser quantities. A characteristic of all
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cereals, however, is that they contain a large amount of carbohydrate and a Food from Plant
Sources
small amount of water/moisture.
The largest proportion of carbohydrate lies in the center, gradually declining
toward the outside of the grain. The protein lies near the outer portion. Fat is
found in small amounts scattered through the entire grain, but most of it is
found in the germ, which is a tiny portion of the grain from which the new
plant sprouts. The mineral matter of cereals is found chiefly just inside the
bran, or outer covering. So, when this covering is removed in the processed
food preparation or processing, a certain amount of mineral matter is generally
lost.
During milling, the bran and germ are removed because bran is ingestible and
the high oil containing germ is susceptible to rancidity. However this process
also removes much of the B vitamins, iron, and dietary fiber. The resulting
grains after milling are known as refined/polished grain. White flour and white
rice are examples of refined grains. Some refined grains are enriched. This
means certain B vitamins (thiamin, riboflavin, niacin, folic acid) and iron are
added back after processing. Fiber is not added back to most enriched grains.
Whole grains, on the contrary contain the entire grain kernel -- the bran, germ,
and endosperm. Examples include whole-wheat flour, bulgur, oatmeal, rye
bread, whole cornmeal and brown rice.
B) Composition
Cereal grains contain carbohydrates, fats, proteins and mineral matter.
Carbohydrates: We have already learnt in the Unit 1 the physiological
functions of carbohydrates in human body. Carbohydrate in the form of starch
is the major food substance found in cereals. Rice with 75 per cent starch
content is the highest starch containing cereal while oats having less than 50
per cent starch has the least starch content. Distributed throughout the grain in
tiny granules, starch is more easily digested than either protein or fat.
However, starch in its natural form is insoluble, tasteless and unsuitable for
human consumption. To make it digestible and acceptable it must be cooked or
processed.
Fats: The fat content provides the heat-and energy-producing qualities in
cereals. Of the important cereals used as food, oats and corn contain the more
amount of fat. The oil of corn, because of its lack of flavor, is frequently used
in the manufacture of salad oil, cooking oil, and pastry fat. The fat that occurs
in cereals becomes rancid if it is not carefully stored. In the making of white
flour, the germ of the wheat is removed. And since most of the fat is taken out
along with the germ, white flour keeps much better than the flour from which
the germ is not abstracted in the milling process.
Proteins: Cereals are essentially a carbohydrate food, but some also yield a
good proportion of protein. Cereal proteins are however deficient in lysine and
methionine. This is in contrast to the food from animals sources that yield
mainly protein, with the exception of milk which yields carbohydrates also.
The grain that contains the most protein is wheat and it occurs as gluten, a
substance that is responsible for the gumminess and elasticity of the wheat
flour when it is mixed with water. The rubbery consistency of bread dough is
also because of gluten. Cereals that contain no gluten do not make good bread.
Rye is only next to wheat in protein content. Rice contains the least. The
protein sourced from cereals is relatively cheap compared to that from other
food sources.
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 Introduction to Food Minerals: Cereals also contain a variety of minerals required for the human
Science body. Much of the mineral matter lies directly under the coarse outside
covering; some of it is lost when this covering is removed in the milling. For
this reason, the grains that remain whole and the cereal products that contain
the entire grain are much more valuable for nutritions reasons. In the diet/dish
if sufficient mineral content is sourced from vegetables, fruits, and milk, it is
perhaps unnecessary to insist on whole cereals. But if the diet is at all limited
in variety, it is advisable to select the whole grain.
Cereals contain very little water/moisture in their composition. This is a
distinct advantage, for it makes their nutritive value proportionately high and
improves their keeping quality. This low proportion of water/moisture allows
them to be stored easily without much chances of spoilage.
2.3.2 Post Harvest Processing
Cereals undergo a number of processing stages between harvest and
consumption. This chain of processes is often referred to as the total post-
harvest system. Each type of cereal requires a specific post-harvest treatment.
However, there are certain general principles that apply to most of them. The
post-harvest processing systems can be split into four distinct areas. The first
involves the preparation of harvested grain for storage. This is further followed
by primary, secondary and tertiary processing. Soon after harvesting, grains
are subjected to threshing and winnowing. Threshing involves the removal of
grains from the rest of the plant whereas winnowing is the separation of the
grains from the chaff or straw and is traditionally carried out by lifting and
tossing the threshed material. In the process, the lighter chaff and straw get
blown to one side while the heavier seeds fall down vertically.
Now the grains are ready for drying and subsequent storage. The most cost-
effective method is to spread out in the sun to dry. In humid climates it may be
necessary to use an artificial dryer. Cereal grains should be dried to 10-14%
moisture before storage. Grains are often stored along with some permitted
insecticides and must be stored in rodent-proof containers.
A) Primary Processing
Primary processing basically involves several different processes designed to
clean, sort and remove the inedible fractions from the grains. It includes
operations like grading, hulling, milling, pounding, grinding, tempering,
parboiling, soaking and drying. After cleaning, the grains are graded according
to the size. Several grains have an unpalatable husk or shell that needs to be
removed by a decorticator. This is known as hulling. After hulling, the grains
are milled.
Milling or pounding is the process of conversion of grain to flour. If the grain
is too dry and hard, it is difficult to break down and requires more energy to
convert it into flour. If the grain is too moist, the material sticks to the mill.
Most grains can be ground in a hammer mill. The milled grain is filtered out
through a perforated plate/sieve that runs around the edge of the mill chamber.
The size of the holes in the perforated plate determines the fineness of grinding
of the particles. Grain for human consumption is ground to a 1mm particle size
while animal feed is ground to a 3mm particle size. Parboiling is another kind
of primary processing that is followed only in rice. Parboiling involves soaking
and heating the rice which pre-cooks the grains, loosens the hull, sterilizes and
preserves the rice. At the village level, parboiling is carried out in large pans
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over an open fire. The products from primary processing are still not Food from Plant
Sources
consumable and require secondary processing.
B) Secondary Processing
The third stage called secondary processing transforms the grains into edible
products. Secondary processing of cereals (or 'adding value' to cereals) is the
utilization of the primary products (whole grains, flakes or flour) to make more
interesting products and add variety to the diet. They were developed
specifically to manage the agricultural surplus and ensure stability of the food
markets in developed countries. Secondary processing of cereals includes the
following processes: flaking, roasting/puffing, frying, baking, fermentation,
and extrusion. These foods require minimum preparation, typically just
heating, and are packaged for a long shelf life with little loss of flavour and
nutrients over time. Puffed rice also known as ‘murmure’ is made by heating
rice in sand-filled ovens. Puffed rice is used in snack foods and breakfast
cereals, and is also a popular street food in some parts. Flaked rice, popularly
known as ‘poha’ is made by a process in which whole rice is cleaned,
conditioned to a suitable moisture and lightly rolled between smooth rolls to
fracture the outer layer. Moisture can then penetrate the grain more readily,
thus help in cooking.
C) Tertiary Processing
During primary and secondary processing of cereals lot of waste and bio-
products are generated. These can be utilized by converting into useful
products. By-products such as broken grains and flours are often used as
animal feed. Rice-hulls are sometimes used as fuel and their ashes as fertilizer.
Rice bran wax is used as wax coating for fruits and vegetables. Rice bran is
used for recovering oil. Defatted bran is utilized as important ingredient for
cattle and poultry feed. Rice is also used industrially in the production of
alcohol, beer, starch, oil and other byproducts
2.3.3 Foods from Cereals
Four general groups of foods are prepared from the cereal grains. (1) Whole-
grain products include rolled oats, brown rice, popcorn, shredded and puffed
grains, and breakfast foods. (2) Milled grain products, made by removing the
bran and usually the germ (or embryo of the seed), include polished rice,
farina, wheat flour, cornmeal, corn grits, pearled barley, semolina (for
macaroni products), prepared breakfast cereals, and soup, gravy, and other
thickenings. (3) Baked products, made from flour or meal, include breads,
pastries, pancakes, cookies, and cakes (4). Beverages such as beer and
whiskey, made from fermented grain products (distilled or un-distilled) and
from boiled, roasted grains (5) other miscellaneous products such as starch,
malt, distilled spirit, livestock feed, and wheat straw.

Check Your Progress Exercise 1 "

Note: a) Use the space below for your answer.
b) Compare your answers with those given at the end of the unit.
1) Define foods.
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 Introduction to Food 2) What are staple foods?
Science
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3) What is difference between Kharif and Rabi crops?

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4) Differentiate between whole grains and refined grains.

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5) If the bran or outer covering of a food grain is removed which is the

nutrient that suffers most?

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6) Cereals are not hard to digest. Explain why?

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7) Name the amino-acids deficient in cereals.

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8) What is primary and secondary processing in cereals?

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2.4 GRAIN LEGUMES

Grain legumes (also called as beans or pulses) are second only to cereals as a
source of human and animal food. Legumes or pulses are general names given
to plants like beans and peas that are distinguished by having their grains in
pods. Beans, lentils, peanuts, peas, and soybeans are some of the common
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legumes consumed by humans. The term pulses, as used by the FAO, is Food from Plant
Sources
reserved for crops harvested solely for the dry grain. This therefore excludes
green beans and green peas, which are considered vegetable crops. Legume
seeds have twice as much protein as grains. They are also high in iron and B
vitamins. Some legumes, such as clover and alfalfa, are used as animal feed.
Split pulses are popularly known as Dals in India (for example, chana dal
[Bengal gram], tuver dal [red gram], mung dal [green gram] and urad dal
[black gram].
In India, legumes/ pulses are being consumed as part of a primarily cereal-
based diet from time immemorial. Legumes/pulses are the main source of
protein and are 2-3 times richer in proteins than cereal grains. Pulses are 20 to
25% protein by weight, which is double the protein content of wheat and three
times that of rice. For this reason, pulses are sometimes called "poor man’s
meat".
The food legumes are classified in two categories: the legumes in which
energy is stored as starch (e.g. pulses) and the ones in which it is stored as fat
or oil (e.g. peanut and soybean). Oilseed legumes are the major contributor to
world edible oil supply as well as protein-rich diets and cattle feed. The soy
bean in India is exclusively used as a source of oil and the meal as a protein
rich animal feed. Inhibitors hold back the popularization of soy bean as a food
legume in Indian diets. The trypsin inhibitors present in the soy bean and their
removal before consuming is a stumbling block. The trypsin inhibitor does not
get destroyed in ordinary cooking. Organoleptic factors such as flavour and
odour, and the presence of flatulence factor also have to be tackled. Special
processes are available to eliminate or at least reduce these factors to a more
acceptable level.
India traditionally has been the largest producer and consumer of pulses (food
legumes) in the world, accounting for 25% of the global output. The current
production of all pulses/ legumes in India at 91.0 million tonnes is inadequate
to meet the huge domestic demand. India is also the world's largest importer
of pulses. Canada, Myanmar, Australia and the United States are significant
exporters of pulses and significant suppliers to India.
Due to a sea-change in the dietary habits in view of the growing health
consciousness and preference for vegetarian proteins, there is an increasing
demand for grain legumes in the developed world not only as food but also for
feed.

2.4.1 Composition of Legumes

Pulses supply the same amount of calories as cereals i.e. 350 kcal per 100 g
(1464.4 kj/100g) dry weight. While pulses are generally high in protein, and
the digestibility of that protein is also high, they often are relatively poor in the
essential amino acid methionine. Grains (which are themselves deficient in
lysine) are commonly consumed along with pulses to form a complete protein.
It is not safe to eat raw or undercooked kidney beans and soya beans because
of the anti-trypsin factor (or trypsin inhibitor) that prevents the assimilation of
the amino acid.
Carbohydrates Content: Legumes usually contain large amounts of
carbohydrates ranging from 24 to 68% and starch is the main carbohydrate
along with oligosaccharides. Oligosaccharide raffinose is predominant in

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 Introduction to Food legumes. It is known to cause indigestion and flatulence that cause discomfort,
Science abdominal rumbling, cramps, pain and diarrhea. Besides they also contain
cellulose and hemicellulose.
Protein Content: The protein content in pulses range from 17 to 30 per cent
about twice or thrice of that in cereals. Soybean with a high of 42 per cent
protein is the highest protein containing pulse. Proteins from legumes generally
have all the essential amino acids, but is deficient in tryptophan, methionine
and cysteine. This deficiency can be made up by taking cereals and pulses
together.
Fat Content: The fat content of most pulses is low i.e. 1-2 per cent, however
some legumes, such as peanuts (with 50 per cent), soybeans (21 per cent) and
winged beans (17 per cent) contain considerable fats. Pulses and legumes are
also a rich source of dietary fiber.
Minerals and Vitamins: Legumes are a good source of minerals such as
calcium, iron, copper, zinc, potassium, magnesium and phosphorous. These are
reputed to lower blood cholesterol and help diabetics by reducing post meal
rise in blood sugar. They are gradually absorbed in the body, resulting in low
rise of blood sugar. Legumes are rich in vitamins especially vitamin B complex
and also beta-carotene and niacin. Germinated chickpea and green gram
contain plenty of ascorbic acid.
Anti-nutritional Factors: Legumes contain some compounds that have a
negative food value. These include protease inhibitors, hemagglutinins,
saponins, cyanogenic glucosides, lathyrogens, phytate, raffinose and tannins.
Most of these anti-nutritional factors can be neutralized by soaking in water
before cooking the pulses. Peanuts, because of their high moisture content at
harvest, may support mold growth and development of toxic metabolites of
molds such as aflatoxins. Heat processing and cooking can help reduce
aflatoxin levels to some extent.

2.4.2 Processing Pulses

In India most of the pulses are consumed in dehusked and split form. Thus
processing of pulses assumes a lot of importance. Pulses processing industry
helps in processing the raw grain legumes/ pulses into edible form. Processing
activity is undertaken at 3 different levels namely primary, secondary and
tertiary. Primary processing involves cleaning, grading and packaging of
pulses. Under secondary processing activities such as dehusking, splitting,
polishing, tumeric/ spices/ salt coating and powdering and packaging are done.
After dehusking and splitting pulses becomes Dals. Tertiary processing mostly
involves activities such as preparation of roasted, fried dals for snack foods and
confectionary. Primarily, Dals are consumed after cooking however they are
utilized for making other value added products such as papads, baris and
besan (fine flour) which is used for making sweets, snacks, and mixed with
wheat flour to make chapattis (flat bread), Dals are widely used in south
Indian foods such as Dosa , vada and idli. Savoury products such as Aloo
Bhujia, Bikaneri Sev, Moong Dal, are prepared from dals.

# Check Your Progress Exercise 2

Note: a) Use the space below for your answer.
b) Compare your answers with those given at the end of the unit.
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1) Classify the legumes on the basis of type of stored energy. Food from Plant
Sources
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2) What are the limitations in use of soybean as a food legume?
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3) Describe different types of carbohydrates found in pulses.

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4) Name anti-nutritional factors present in pulses.
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5) Name two essential amino acids lacking in legumes.
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2.5 OILSEEDS: CHARACTERISTICS

The crops cultivated for production of oils are known as oilseed crops.
Oilseeds rank next to the food grains in importance in the Indian diet.
According to the nature of the yielded oil, these are classified as edible
oilseeds and non-edible oilseeds. The rapeseed, mustard, sesame, sunflower,
niger, safflower, coconut, soybean and groundnut are the most important edible
oilseeds crops grown in India. Castor and linseed are two most important non-
edible oil crops. Fats and oils are important energy source for animals and
plants, and accounts for 21/4 times the calories found in an equal dry weight of
protein or carbohydrate. They are smooth, greasy substances that are insoluble
in water.
Fats have other substances associated with it, such as fat-soluble vitamins A,
D, E and K in natural foods; the sterols, cholesterol in animal fats and
ergosterol in vegetable fats. A typical fat molecule consists of glycerol
combined with three fatty acids. There are about 20 different common fatty
acids that are connected to glycerol in natural fats. These fatty acids differ in
length and in number of hydrogen atoms they contain. The chemical variations
in fats lead to different functional, nutritional and keeping-quality properties.
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 Introduction to Food The difference in melting point arises because of this variation. The longer the
Science fatty acids chain, the harder the fats, and shorter the chain, softer the fats.
Vegetable oils are fats of plant origin and remain in liquid form at room
temperature, whereas fats of animal origin remain solid at that temperature
level. There are some exceptions, however. For instance, coconut oil is solid at
room temperatures in colder months because it has a melting point of 24-27oC.
On the other hand, fish fats or oils are liquids at room temperature. Generally,
the reason that some fats are solids and others are liquids at room temperature
has to do with the percentage of saturated or unsaturated fatty acids in the fat.
Unsaturated fatty acids with four or more carbon atoms that can accept
hydrogen are more reactive than saturated fatty acids and are especially
capable of combining with oxygen present in the atmosphere. This is the case
when a carbon saturated with hydrogen is present between two carbons, each
of which could accept hydrogen or free electron -CH=CH-CH2-CH=CH-.
When the unsaturated fatty acids in fats become oxidized, the fat generally
becomes rancid or has an off-flavour. Oils, therefore, should be stored at
ambient temperature in sealed, preferably dark-coloured containers to prevent
oxidation. Re-used oils need to be strained to remove impurities that could lead
to oxidation and associated rancidity. Oils that have been used frequently for
deep frying should be discarded. Vegetable oils are often a rich source of
unsaturated fatty acids, although some saturates are also present. Vegetable
oils usually contain natural antioxidants such as vitamin E, which helps the oils
resist rancidity (which occurs when oxidation takes place). Sometimes a blend
of oils is used in a product to take advantage of the desirable characteristics of
the different types of oils.
Some important properties of fats are:
1) All fats and oils have unique flavours and odours. Some are more suited for
particular purposes than others, e.g. olive oil for salad dressing (for
flavour) and mustard oil for frying.
2) Fat has shortening power; that is, it interlaces between protein and starch
structures and makes them tear apart easily, and allows them to stretch
long. In this way, fat tenderizes meat as well as baked goods.
3) Fat is a lubricant in foods; that it makes swallowing of carbohydrates easier
while eating.
4) Fats gradually soften on heating, that is they do not have a sharp melting
point. This property is called plasticity, and gives each fat its unique
character. Some fats have been formulated so that their melting points are
low and they can be spread straight from the fridge, e.g. soft margarine,
‘spreadable butter’.
5) Fats can be heated substantially above the boiling point of water, so they
can brown the surfaces of foods.
6) Fats form emulsions with water and air. Fat globules may be suspended in
a large amount of water as in milk or cream, or droplets of water may be
suspended in a large amount of fat as in butter. Air may be trapped as an
emulsion in fat as in butter, cream, icing or in whipped butter.
7) Fats and oils are used in confectioneries and cakes to give these products
opacity, flavor and desirable texture. Addition of fat to sugar confectionery
also helps to prolong eating quality.
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8) Some vegetable oils are richer in fatty acids that are extremely good for Food from Plant
Sources
health e.g. omega-6 fatty acids (e.g. sunflower and corn oils) and omega-3
fatty acids (e.g. rapeseed oil and soya oil). Other oils are rich in
monounsaturated fatty acids (e.g. olive oil, rape seed oil, groundnut oil).

2.5.1 Processing of Oilseeds

Processing of oilseeds may vary with raw material however some general steps
are common to all. The first step involves, preparation of the raw material;
removal of fine impurities, husks or seed coats from the seeds and separating
the seeds from the chaff. The seeds are then cracked to expose the “meats” of
the raw material. Oil is then extracted mechanically with an oil press, an
expeller. Presses range from small, hand-driven models that an individual can
build to power-driven commercial presses. Expellers have a rotating screw
inside a horizontal cylinder that is capped at one end. The screw forces the
seeds or nuts through the cylinder, gradually increasing the pressure. The
material is heated by friction and/or electric heaters. The oil escapes from the
cylinder through small holes or slots, and the press cake emerges from the end
of the cylinder. Oils can also be extracted with solvents, but solvent extraction
is a complex operation and not suitable for small scale processor. After
extraction oils are clarified to remove contaminants, such as fine pulp, water,
and resins. Sealed glass or plastic bottles are adequate. Colored containers in a
dark box help to increase shelf life. Seed cake is a valuable by-product of
pressing and makes a good chicken, pig, or cattle feed. Oil finds wide uses as
food, skin care products, aromatherapies, biodiesel fuels, and industrial
lubricants.

Check Your Progress Exercise 3

"
Note: a) Use the space below for your answer.
b) Compare your answers with those given at the end of the unit.
1) Name two edible and two non-edible oilseeds crops.
………………………………………………………………………………………………
………………………………………………………………………………………………
………………………………………………………………………………………………

2) Name two vegetable oils rich in omega-6 fatty acids.

………………………………………………………………………………………………
………………………………………………………………………………………………
………………………………………………………………………………………………

3) Name two vegetable oils rich in monounsaturated fatty acids.

………………………………………………………………………………………………
………………………………………………………………………………………………
………………………………………………………………………………………………

4) Differentiate between animal and vegetable fats.

………………………………………………………………………………
………………………………………………………………………………
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39
 Introduction to Food 5) What is rancidity? How can it be overcome?
Science
………………………………………………………………………………
………………………………………………………………………………
…………………………………………………………………………….…
6) What is shortening?
………………………………………………………………………………
………………………………………………………………………………
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2.6 HORTICULTURAL CROPS: STRUCTURE

AND COMPOSITION
A range of crops including fruits, vegetables, flowers, ornamental plants,
plantation crops is grouped as Horticultural crops. These crops play an
important role in the national economy and are important drivers of growth.
The total annual production of horticultural crops in the country is around 149
million tonnes. Fruits and vegetables are the principal horticultural crops. The
two together provide the base for nutritional and healthy foods, but also
generate a considerable cash income for growers. India is the second largest
producer of fruits (45.5 million tonnes) and vegetables (90.8 million tonnes),
accounting for 10.23 per cent and 14.45 per cent respectively of the world
production.
Plantation crops are perennial crops, planted on large-scale or in estates. Its
objective is meant for large-scale production of a single cash crop. This often
involves large landowners, raising crops of high value and great economic
importance. These crops usually require a sequence of post harvest processing
before they can be utilized. Tea, coffee, rubber, coconut, arecanut, cashewnut,
black pepper, and cardamom are some of the important plantation crops. India
is the largest producer of areca nut, cashew nut and tea and second largest
producer of coconut and cardamom in world.
Fruits and Vegetables
Botanically, fruits are the mature ovaries containing the seeds of the plants
whereas vegetables are derived from various plant parts such as root, leaves,
stems, buds and so on. Fruits and vegetables make up a significant part of the
diets of most cultures. Fruits include soft fruits (raspberry, blackberry,
redcurrant, strawberry and bilberry), citrus fruits (orange, lime, lemon,
kumquat and grapefruit), stone fruits, (plum, apricot, peach, lychee, cherry and
mango), fleshy fruits (apple, papaya, pineapple, pear and banana) and vine
fruits (grape, water melon and cantaloupe). Vegetables include root vegetables
(carrots, sweet potatoes), leaf vegetables (such as spinach and lettuce), stem
vegetables (such as bamboo shoots and asparagus), and inflorescence
vegetables (such as globe artichokes and broccoli). Some fruits, such as
tomato, pumpkin and eggplant, are also eaten as vegetables. Many herbs and
spices have proved to be highly-flavored vegetables.

40
An important distinction between fruits and vegetables is based on their usage: Food from Plant
Sources
those plant items that are generally eaten with the main course of meal are
often considered to be vegetables; those commonly eaten alone as a dessert are
considered as fruits. Fruits are generally acidic and sugary whereas vegetables
are low in acids and sugar.
Vegetables are rich in vitamin A, ascorbic acid, protein (legumes) and fiber.
Carrots, sweet potatoes, green leafy vegetables and tomato are best sources of
Vitamin A. Among vegetables, Hot chili peppers, turnip greens and spinach
are also good sources. Sweet peppers, hot chilies, broccoli, brussel sprouts and
cauliflower and bittergourd are prominent sources of vitamin C. Vitamin B is
found in green peas, lima beans, turnip greens, spinach and sweet potato.
Potato is an important source of potassium for people in many countries. Lima
beans, soybeans and spinach are good sources of iron. Calcium is present in
moderate amounts in turnip greens, soybeans, garlic, parsley and chinese
cabbage. Fruits and vegetables are equally good sources of dietary fiber. We
already have seen the importance of dietary fiber in previous Unit. Scientific
studies have consistently shown that consumption of diets rich in dietary fiber
can help reduce the risk of cardiovascular diseases, diverticulosis and colon
cancer. A more obvious effect of dietary fiber is their laxative action, which
helps relieving of constipation by increasing the water-holding capacity of
foods.

2.6.1 Post Harvest Technology

Fruits and vegetables are different from cereals, pulses and oilseeds. Generally
they cannot be stored for longer periods and should be used as soon as
possible. If stored, they should be kept in a cool, dark place to prevent
sprouting, mould growth and rotting. Since they are tender and high in
moisture content they are highly perishable. If not handled properly, a high
value nutritious product can deteriorate and rot in a matter of days or even
hours. Some fruits such as coconut and citrus (with a protective rind) can be
handled and shipped reasonably well. Post harvest losses can occur in the field,
in packing areas, in storage, during transportation, and in wholesale or retail
markets. Therefore, a series of sophisticated technologies have to be applied in
post harvest handling of horticultural crops. Fruits and vegetables breathe like
humans do, respiring day and night, continuously giving off water as they
release energy for growth and metabolism. In respiration, plants use oxygen to
break down carbohydrates, proteins, and fats into carbon-dioxide and water.
Respiration leads to drying out, wilting and shriveling, less food value and less
sweetness. This leads to loss of quality and freshness. Mechanical injuries such
as abrasion, puncture and bruising lead to more water loss. Also wounded and
punctured areas are more prone to be attacked by bacteria and fungi. Apart
from these, there are other factors that lead to loss in quality. These include
inefficient crop production, harvesting and handling methods, poor crop
processing techniques, inadequate methods of storage and transportation and
even poor preparation procedures. Traditional marketing systems often
contribute to reduced returns to farmers, by involving several changes of
hands. Modern post harvest technologies applied in grading, packaging, pre-
cooling, storage, and transportation, minimize losses, and preserve quality.

Another useful approach to minimize post harvest loss of horticultural

commodities is to add value to products. Value addition involves change of
form of a product, converting raw material into ingredients or processed
41
 Introduction to Food products to cater to demands of heterogenous consumers. Value addition offers
Science numerous advantages to the growers and consumers. Value added products
have extended shelf life, improved quality, and palatability. Farmers can derive
high farm income from their produce by adding value to their products by way
of cleaning, trimming, processing, and packaging. Post-harvest value addition
includes primary, secondary, and tertiary processing, operations performed on
farm produce. Primary processing refers to on-farm handling, cleaning,
trimming, sorting, grading, cooling and packaging whereas secondary
processing includes processes which modify the form of the product i.e.
convert raw product to a processed products. Processed products offer cent
percent edible product, are convenient, and have improved eating quality.
Jams, jellies, marmalades, sauces, ketchups, cordials, juices, nectars, pickles,
candies, preserves, canned, frozen, dried, and fermented products are examples
of secondary processed products.

# Check Your Progress Exercise 4

Note: a) Use the space below for your answer.
b) Compare your answers with those given at the end of the unit.
1) Name some important plantation crops?
………………………………………………………………………………
………………………………………………………………………………
………………………………………………………………………………
…………………………………………………………………………….…
2) Analyze the main causes of post harvest losses in fruits and vegetables.
………………………………………………………………………………
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………………………………………………………………………………
…………………………………………………………………………….…
3) What are important post harvest technologies used to minimize loss of
fruits and vegetables?
………………………………………………………………………………
………………………………………………………………………………
………………………………………………………………………………
…………………………………………………………………………….…
4) What does secondary processing of fruits and vegetables refers to?
………………………………………………………………………………
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…………………………………………………………………………….…
………………………………………………………………………………
42
 Food from Plant
2.7 LET US SUM UP Sources

Cereal grains, pulses, oilseeds and horticultural crops are important foods from
plant sources. Together cereal grains, pulses, oilseeds and horticultural crops
provide us much needed carbohydrates, proteins, fats and vitamins and
minerals for human nutrition. Pulses are 2-3 times richer in protein than
cereals. A combination of cereals and pulses also complements the diet in
respect of amino-acids lacking in respective diets. Cereals grains are compact
and dry and can be easily handled transported and stored or long periods in
comparison to horticultural crops. The shelf life of horticultural crops is
limited because of their moisture content and respiration activities. Secondary
processing adds value to cereals and transforms grain to edible products such
as breakfast cereals, puffed, flaked, fried and extruded products. Horticultural
crops require a range of modern post harvest technologies applied in grading,
packaging, precooling, packaging, storage and transportation to minimize
losses and preserve quality.

2.8 KEY WORDS

Food : Food is any substance, primarily composed of
carbohydrates, fats, water and/or proteins, that can
be eaten or drunk by an animal or human being for
nutrition or pleasure.

Caryopsis : The cereal grain is one seeded indehiscent fruit

called caryopsis. In this the pericarp is completely
fused with the seed coat.

Hulling : The process of removing an unpalatable husk or

shell around the cereal grain.

Anti-nutritional Factor: Some compounds found in pulses that reduce their

biological value.

Milling : The conversion of grain into flour.

Parboiling : A primary treatment given to rice to improve its

keeping quality and nutritional value. Parboiling
involves soaking and heating the rice which pre-
cooks the grains, loosens the hull, sterilizes and
preserves the rice.

Gluten : A protein found in wheat.

Puffing : The process of making a puffed ready-to-eat

product from rice.

Flaked Rice : A popular breakfast cereal known as ‘poha’ from

rice. The process involves rolling the conditioned
rice to fracture the outer cells.

Plasticity : A unique property of oils, wherein oils gradually

soften on heating, because they do not have a
sharp melting point.
43
 Introduction to Food
Science # 2.9 ANSWERS TO CHECK YOUR PROGRESS
EXERCISES
Check Your Progress Exercise 1
Your answer should include following points:

1) Food is any substance, primarily composed of carbohydrates, fats, water

and/ or proteins, that can be eaten or drunk by an animal or human being
for nutrition or pleasure.

2) Cereals grains are grown in greater quantities and provide more energy
worldwide than any other type of crop; they are, therefore, also known as
‘staple foods’

3) Crops sown in rainy or summer seasons (April-July) and harvested in

winters (October) are kharif crops e.g. rice. Rabi crops are those which are
sown in winters (October to February) and harvested in summers are rabi
e.g. wheat

4) Whole grains are grains comprising of the entire kernel- the bran, germ and
endosperm whereas refined grains donot comprise of the entire grains.
During milling, bran and germ are removed. Whole grains are more
nutritious than refined grains because minerals largely present in the outer
bran are retained.

5) Minerals are lost when the outer covering of a food grain is removed

6) Cereals are not hard to digest because they are rich in carbohydrate starch.
Starch is more easily digested than either protein or fat. Furthermore,
cooking and processing makes the starch more digestible and acceptable.

7) Lysine is lacking in cereals.

8) Primary processing of cereals is a term given to set of operations involving

cleaning, grading, hulling, milling, pounding, grinding, parboiling, soaking
and drying. The products from primary processing are not consumable.
Secondary processing is advanced processing and transforms grains into
edible products. It includes operations like fermentation, baking, puffing,
flaking and frying.

Check Your Progress Exercise 2

Your answer should include following points:

1) The food legumes are classified in two categories: the legumes in which
energy is stored as starch (e.g. pulses) and which energy is stored as fat or
oil (e.g. peanut and soybean).

2) Soybean contains anti-nutritional factors such as trypsin inhibitors which

are not destroyed on ordinary cooking. Also there are unacceptable factors
such as taste, odor and flatuence factor, which further limits its acceptance.

3) The major carbohydrates found in legumes are starch, raffinose, cellulose

and hemicellulose.
44
4) Pulses contain protease inhibitors, hemagglutinins, saponins, cyanogenic Food from Plant
Sources
glucosides, lathyrogens, phytate, raffinose, tannins and aflatoxin.
5) Methionine and tryptophan are essential amino acids lacking in legumes

Check Your Progress Exercise 3

Your answer should include following points:
1) The rapeseed, mustard, sesame, sunflower, niger, safflower, coconut,
soybean and groundnut are the most important edible oilseeds crops of
India whereas castor and linseed are two most important non-edible oil
crops.
2) Sunflower and corn oils are rich in omega 6 fatty acids
3) Olive oil and groundnut oil are rich in monounsaturated fatty acids
4) Vegetable oils are mainly of plant origin and are liquid at room
temperature whereas fats are mainly of animal origin and are usually
solids. Vegetable oils have more unsaturated fatty acids whereas animal
fats have more saturated fatty acids.
5) When the unsaturated fatty acids in fats oils become oxidized, the fat
undergoes rancid and has an off-flavour. Fats and Oils, therefore, should be
stored at ambient temperature in sealed, preferably dark-colored containers
to prevent rancidity.
6) Fats interfaces between protein and starch structures and makes them tear
apart easily and short rather than allow them to stretch long. In this way, fat
tenderizes meat as well as baked goods. This is property of fat is known as
shortening.

Check Your Progress Exercise 4

Your answer should include following points:

1) Plantation crops are perennial crops, planted on large-scale or estate,

meant for large-scale production of a single cash crop. Most of these
involve a large landowner, raising crops with high value and great
economic importance rather than for subsistence. These crops usually
require a sequence of post harvest processing before they can be utilized.
Tea, coffee, rubber, coconut, areca nut, cashew nut, black pepper, and
cardamom are some of the important plantation crops.

2) The main causes of post harvest losses in fruits and vegetables include
inefficient crop production, harvesting and handling methods, poor crop
processing techniques, inadequate methods of storage and transportation
and even poor food preparation procedures.

3) Modern post harvest technologies applied in grading, packaging, pre-

cooling, storage, and transportation, which minimize losses, preserve
quality.

4) Secondary processing refers to value added products such as Jams,

jellies, sauces, ketchups, cordials, juices, nectars, pickles, canned, frozen,
dried baked and fermented products.

45
 Introduction to Food
Science
2.10 SOME USEFUL BOOKS
Ron Wills, Barry Mc Glasson, Doug Graham, Daryl Joyce. (1998)
Introduction to the Physiology and Handling of Fruits, Vegetables and
Ornamentals. 4th Edition, CAB International Wallington Oxon. U.K.

Norman N. Potter and Joseph H Hotchkiss (1997) Food Science. 5th Edition,
Chapman & Hall Publishing Inc, New York, USA.

John T.R Nickerson and Louis J. Rensivalli (1995) Elementary Food Science.
AVI Publishing Company, Westport, Connecticut, USA

Peter Golob, Graham Farrell and John E Orchard (2002) Crop Post Harvest:
Science and Technology. Blackwell Publishing, U.K.

46