Introduction

No one knows exactly when ice cream was first produced. Ancient manuscripts tell us that
the Chinese liked a frozen product made by mixing fruit juices with snow – what we now call
water ice. This technique later spread to ancient Greece and Rome, where the wealthy in
particular were partial to frozen desserts.
After disappearing for several centuries, ice cream in various forms reappeared in Italy in the
Middle Ages, most probably as a result of Marco Polo returning to Italy in 1295 after some
17 years in China, where he had acquired a liking for a frozen dessert based on milk. From
Italy, ice cream spread through Europe during the 17th century, long remaining a luxury
product for the royal courts. Industrial ice cream production began at the end of the 19th
century when the first mechanical refrigerators were pioneered.

Ice cream is defined as a frozen dairy product made by suitable blending and processing of
cream and other milk Products, together with sugar and flavor, with or without stabilizer or
colour, and with the incorporation of air during the Freezing process

According PFA- Rules (1976). Ice cream may is a frozen dessert obtained from cow/buffakee
milk or a combination
(Or)
form cream & other milk products, with or without addition of cane sugar, eggs (fruits, fruit
juices, preserved fruitsts, nuts, chocolate, edibile flavours & permited food colours. It may
contain permitted Stabilizers and emulsifiers not exceeding 0.5% by weight.

The mixture must be suitably heated before freezing. The product should contain not less
than 10 percent milk fat, 3.5 % protein and 36% total solids.
when the preparation contain fruits or nuts or both, the content of milk fat may be reduced ,
but not less-than 8% by weight.
starch may be added to a maximum extent of 5 % with a declaration to that effect on the
label.
Classification
CATEGORIES OF ICE CREAM AND RELATED PRODUCTS
Ice cream and related products can be divided into a number of categories. As legislation
varies from one country to another, the following should be regarded as a guideline only.
The fat content of ice cream typically determines the category to which it belongs. In some
countries fat content has to exceed 9% to "qualify” for the ice cream category. Below this
level, the product is typically called milk ice, whereas ice cream with more than 12 to 13%
fat is often categorized as either luxury or premium.
The fat can be either of animal or vegetable origin. If the latter, legislation in a number of
countries dictates that the product cannot then be called ice cream, but must be labelled, for
example, non-dairy ice cream or frozen dessert.

No standard classification of ice cream has yet been adopted by the industry, even in
developed countries. However, some of the import ant frozen desserts can be classified as
follows: (i) Plain. An ice cream in which the colour and flavouring ingredients together
amount to less than 5 per cent of the volume of the unfrozen ice cream. Examples: Vanilla
and Cuffee ice creams.
(i) Chocolate. Ice cream flavoured with cocoa or chocolate.
(iii) Fruit. Ice cream containing fruits, with or without additional fruit flavouring or colour.
Fruits such as strawberry, apricot, pineapple, mango, banana, etc., may be fresh,
frozen-packed, canned or preserved.
(iv) Nut. Ice cream containing nuts, such as almonds, pistachio. walnuts, cashewnut, etc.,
with or without additional flavouring or colour.
(v) Milk ices or milk lollies. According to the PFA rules (1976). these refer to the frozen
product obtained from milk, skim milk or milk products with or without the addition of cane
sugar, eggs, fruits, fruit juices, nuts, chocolates, edible flavours, and permitted food colours.
It may contain permitted stabilizers not exceeding 0.5 per cent of the product. The mixture
should be suitably heat-treated be fore freezing. The product should contain not more than 2.0
per cent milk fat, not less than 3.5 per cent proteins and not less than 20.0 per cent total
solids. (vi) Ices. Made of fruit juice, sugar and stabilizer, with or without additional fruit acid,
colour, flavouring or water, and frozen to the consistency of ice cream. Usually contain 28 to
30 per cent sugar, 20 to 25 per cent overrun and no dairy products.
(vii) Sherbet. Made of fruit juices, sugar, stabilizer, and milk products. It is similar to an ice
except that milk, either whole, skim, condensed or powdered, or ice cream mix, are used in
place of all or part of the water in an ice..
(viii) Fancy moulded. Moulded in fancy shapes and composed either of one colour and
flavour of ice cream or a combination of colours and flavours, or especially decorated.
Examples are: brick ice cream, cakes, cake roll, moulds representing fruits, etc.
(ix) Novelties. A Novelty ice cream or frozen confection is an especially shaped and usually a
low-priced package containing an individual serving whose main appeal consists in its shape,
size, colour or convenience for eating.
(x) Soft ice cream (Softy). Sold as drawn from the freezer without hardening.
ICE CREAM TERMINOLOGY
Depending on the filling method, ice cream products fall into one of the following categories:

MOULDED
Ice cream or water ice mix is filled into moulds and frozen to produce stick novelties. After
extraction, the products can be dipped in chocolate or other coatings.

FILLED
Ice cream is filled into cups, cones or containers/tubs, often combined with more flavours and
may be decorated with chocolate, cream, ripple and dry materials.

EXTRUDED
Ice cream is typically extruded onto a tray by means of extrusion with a cutter. A wide variety
of products can be produced including stick novelties, sandwiches, desserts, ball-top cones
and so on. Extrusion technology provides the possibility to work with ice cream drawn at
much lower temperature where the viscosity of the ice cream is high due to more water being
frozen into ice crystals. This generates ice creams that are both smoother due to smaller ice
crystals and creamier due to higher churning of fat compared to moulding and filling
technologies. The higher viscosity also offers the possibility to work with detailed forms and
flavours, decorations and coatings.
RECEPTION AND STORAGE OF RAW MATERIALS
The manner in which raw materials and ingredients are received varies from one factory to
another depending on its facilities and capacity.
Dry products are usually delivered in bags. Bulk materials such as sugar and milk powder can
be delivered in containers and blown into storage silos using compressed air.
Liquid products are often delivered in tankers. Milk products are stored below 5°C during
storage, while sweetened condensed milk, glucose and vegetable fat must be heated to a
relatively high temperature (30 to 50°C) to keep the viscosity low enough for pumping. Milk
fat is delivered in the form of anhydrous milk fat (AMF) or blocks of frozen butter, which are
melted prior to use and pumped into storage tanks, where a temperature of 35 to 40°C must
be maintained.
Composition
The composition of ice cream is usually expressed as a percentage of its constituents, i.e. a
percentage of milk fat, milk-solids-not-fat (serum solids), sugar, stabilizer, total solids, etc. Its
composition varies in different localities and in different markets. The best ice cream
composition for a manufacturer to produce is often difficult to establish. After consideration
of legal requirements, quality of product desired, raw materials available, plant procedures,
trade demands, competition and cost, there is a choice of a product of minimum, average or
high fat/solids composition. Some factories may choose to manufacture only one of these
products, others two and still others all three, i.e. an economy-brand product, a good average
composition product as a trade brand, or a deluxe high quality product.
It may be inadvisable for a small manufacturer to produce more than one brand of ice cream.
If only one is manufac tured, it is extremely important that every effort be made to produce
the best product possible.
In ice cream, the percentage of milk fat varies more than any other constituent. As the fat
content is increased, the milk-solids not-fat must be decreased so as to avoid 'sandiness' (i.e.
the crys tallization of milk sugar or lactose in the finished ice cream). Table 6.1 gives the
composition of economy and good average ice creams.
RAW MATERIALS AND INGREDIENTS
The ingredients used in ice cream production are:

Fat
Milk solids non-fat (MSNF)
Sugar/non-sugar sweetener
Emulsifiers/stabilizers
Flavours
Colours
Other ingredients
FAT
Fat makes up about 10 to 15% of an ice cream mix and may be milk or vegetable fat. The fat
gives creaminess and improves melting resistance by stabilising the air cell structure of the
ice cream.
Milk fat is used in the form of whole milk, cream, butter or anhydrous milk fat (AMF). Milk
fat can be replaced by vegetable fat, where refined or hydrogenated (hardened) coconut oil
and palm kernel oil are most commonly used. The use of vegetable fat in ice cream is
regulated by legislation in many countries.

MILK SOLIDS-NON-FAT (MSNF)

MSNF consist of proteins, lactose and mineral salts derived from whole milk, skim milk,
condensed milk, milk powders and/or whey powder. In addition to its high nutritional value,
MSNF helps to stabilize the structure of ice cream due to its water-binding and emulsifying
effect. The same effect also has a positive influence on air distribution in the ice cream during
the freezing process, leading to improved body and creaminess.
In a well-balanced recipe, the quantity of MSNF should always be in proportion to the water
content. The optimal level is 17 parts MSNF to 100 parts water:

SUGAR
Sugar is added to increase the solids content of the ice cream and give it the level of
sweetness consumers prefer. Ice cream mix normally contains between 12 to 20% sugar.
Sugar is the common description for the saccharides, including the monosaccharides (i.e.
glucose/dextrose and fructose), disaccharides (i.e. sucrose and lactose (milk sugar)) and
starch derivates (i.e. glucose syrup, glucose/fructose syrup and high fructose syrup).
The consistency of the ice cream can also be adjusted by selecting different types of sugar.
This makes it possible to produce ice cream that is easy to scoop.
In the production of sugar-free ice cream, sweeteners are used to replace sugar. Aspartame,
acesulfame K and sucralose are the most commonly used sweeteners in ice cream and are
applied in conjuction with a bulking agent such as malto-dextrin, poly-dextrose, sorbitol,
lactitol, glycerol or other sugar alcohols.
EMULSIFIERS AND STABILIZERS
Emulsifiers and stabilizers are typically used as combined products at dosages of 0.5% in the
ice cream mix. Traditionally, these products were produced by dry blending, but today
integrated products are preferred due to the improved dispersion and high storage stability.
The purpose of adding stabilizing in ice cream is to obtain smooth body and texture. They
help in improving the water holding ability of ice cream mix and thereby help to obtain
smooth body and texture.
They also help to prevent large ice crystal formation during storage of ice cream.
Excess amount of stabilizer would cause soggy or gummy body in ice cream
and reduce whipping ability. Whipping ability of ice cream mix refers to the
ease with which air can be incorporated into ice cream mix. The size of the air
cells and the maximum overrun, which can be attained.
Emulsifier helps to emulsify fat in ice cream mix. It improves the whipping
ability and provides a dry ice cream with smooth body and texture. Too
much of emulsifier may cause excessive foaming in ice cream and cause shrinkage
during storage.
Emulsifiers
Emulsifiers are substances that assist emulsification by reducing surface tension between two
phases. There exists several different emulsifier types utilized in ice cream production, but
the far most dominant and probably most effective emulsifier is the mono-/diglyceride of
fatty acids. The mono-/diglyceride is often derived from a a vegetable fat (triglyceride) where
fatty acid chains have been removed, creating a molecule that has a lipophilic end (fat loving)
and a hydrophilic part (water loving). The mono-/diglyceride has two main functions during
ice cream processing, where it assists the dairy protein displacement from the fat surface
membrane, in order to improve the churning during the freezing process. The
mono-/diglycerides also seed the crystallization of fat, which is essential for avoiding
overchurning of the fat during the freezing process. Egg yolk is a well-known emulsifier, but
is expensive and less effective than the most commonly used types.

Stabilisers
A stabilizer is a substance that has the ability to bind water when dispersed in a liquid phase.
This is called hydration and means the stabilizer forms a matrix that prevents the water
molecules from moving freely. Most of the stabilizers utilized for ice cream are large
molecules derived from seeds, wood or algae/seaweed. Stabilizers are used in ice cream
production to increase the viscosity of the mix and create body and texture. They also control
the growth of ice crystals and improve melting resistance.
FLAVOURS
Flavours are a very important factor in the customer’s choice of ice cream and can be added
at the mixing stage or after pasteurization. The most popular flavours are vanilla, chocolate
and strawberry.
Flavour is an important aspect of ice cream.
Ice cream is valued mainly for the pleasing flavour. Many flavours, both natural
and artificial are available for providing flavour substance for ice cream. In the
selection of flavouring material, it is important to consider the quality of ice
cream mix in which they are to be used. Slight off-flavours in the mix may
obscure the delicate flavour of the flavouring material. Flavouring substances
of natural and artificially produced are available mainly in mixtures for flavouring
food products
In the EU, flavours are classified in three groups: natural, nature-identical and artificial.
Nature-identical flavours are the most commonly used.
The most common ice cream flavours are vanilla, nougat, chocolate, strawberry and nut.
COLOURS
Ice cream should have a delicate attractive colour which suggests or
is associated with the flavour. Only harmless, edible and permitted food colours should be
used. Care should be taken to use only those colours, which are permitted under PFA rules.
Natural or artificial colours are added to the mix to give the ice cream an attractive
appearance. Local legislation exists in most countries regarding the use of colours in food.
OTHER INGREDIENTS
Many moulded and extruded ice cream products are coated with chocolate. Two types of
chocolate coatings are used: real chocolate and chocolate compound. The cocoa mass and
butter are replaced with a blend of cocoa powder and vegetable fat in the chocolate
compound.
Ripples (sauces) are incorporated in ice cream for taste and appearance. They can also be
applied for pencil filling and top decoration.
Dry ingredients are either added through an ingredient doser or as top decoration matter on
cones, cups and bars. A great variety of products are used: chocolate, nuts, dried fruit pieces,
candies, cookies, Smarties, caramel pieces, etc.
Preparation of ice cream mix
Ice cream is composed of a mixture of both dairy and non-dairy food ingredients
such as milk products, sweetening agents, stabilizers, emulsifiers, flavours and
colouring materials. As already seen earlier, wide variety of ingredients could be
used to produce ice cream mix. The effect of these ingredients upon the finished
product is due to the constituents of the ingredients.
An ice cream mix is the unfrozen blend of the different ice cream ingredients. It
consists of all the ingredients of ice cream with the exception of flavour material and
air. Flavour is added only at the time of freezing and air is incorporated into the mix
during freezing. The composition of ice cream is usually expressed as percentage of
its constituents. A satisfactory composition produces an ice cream having desired
flavour body and texture characteristics. An ice cream mix with such a satisfactory
composition is called a “Balanced mix”. Thus a balanced ice cream mix is one in
which the proportions of the constituents and ingredients are such that they combine
to produce an ice cream of satisfactory quality.i) Calculation of Mix-Ingredients: To prepare
ice cream mix various ingredients are mixed. It is necessary to know how much of each
ingredient should be
added to produce a balanced mix. Addition of exactly calculated amount of
ingredients will help to produce ice cream of uniform quality. This will also ensure ice cream
produced meets the legal standards prescribed for ice cream.
Knowledge of calculation, therefore, is helpful in properly balancing the ice
cream mix.
Algebraic method is one method for calculating the amount of ingredients
required for ice cream preparation.
The final composition desired in ice cream is decided first. Suppose ice cream
with the following composition is to be prepared:
Fat – 12.0%
SNF – 11.0%
Sugar – 15.0%
Stabilizer & Emulsifier v 0.5%
Total = 38.5%
The ingredients available are:
Milk – 3.5% fat; 8.5% SNF
Cream – 40.0% fat; 5.28 SNF
Skim milk powder – 1.0% fat; 96.0% SNF
Sugar, Stabilizer + Emulsifier – It is assumed that sugar, stabilizer
and emulsifier contribute 100% solids.
It is convenient to calculate the required amount of ingredients for preparing
100 kg of ice cream mix.
ii) Calculation for 100 kg Ice cream mix: Since sugar and stabilizer + emulsifier
in the mix are 15.0% and 0.5% respectively, the ice cream mix will have 15.0
Kg sugar and 0.5 Kg stabilizer + emulsifier. It means that out of 100.0 Kg of
mix, 15.5 Kg comes from the mixture. The balance of (100 –15.5) kg== 84.5
Kg comes from the mixture of milk, cream and skim -milk powder.
Assume A Kg milk, B Kg cream and C Kg skim-milk powder are used.
The values for A, B and C could be calculated by forming algebraic equation
and solving the equation.
In 100 Kg ice cream mix the following will be there:
Milk – A Kg
Cream – B Kg
Skim milk powder – C Kg
Sugar – 15.0 Kg
Stabilizer + emulsifier – 0.5 Kg
Total = 100 Kg
A + B + C + 15.0 + 0.5 = 100.0
or A + B C = 100.0 – (15.0 + 0.5)
or A + B C = 84.5 — Equation (1)
In 100 Kg of mix 12 Kg milk fat (12%) is present. This amount comes from A Kg
milk, B Kg cream and C Kg skim milk powder. Since the fat percent in each
ingredient is known an equation for fat can be made.

3.5 40.0 1.0 A B C 12

100 100 100

or 3.5 × A + 40.0 × B + 1.0 × C = 1200 Equation (2)

Similarly equation for SNF content is formed:
8.5 5.28 96.0 A B C 11
100 100 100

8.5 5.28 96.0

or 8.5 × A + 5.28 × B + 96.0 × C = 1100 Equation (3)
To eliminate one known value (Say A) multiply the equation (1) by 3.5
i.e. 3.5 (A + B + C) = 84.5 × 3.5
or 3.5 × A + 3.5 × B + 3.5 × C = 84.5 × 3.5 = 295.75
Subtract this equation from equation (2)
3.5 × A + 40.0 × B + 1.0 × C = 1200.00
3.5 × A + 3.5 × B + 3.5 × C = 295.75
36.5 × B – 2.5 × C = 904.25 Equation (4)
Similarly to eliminate A from equation (3) multiply equation (1) by 8.5 and subtract
from equation (3).
8.5 (A+B+C) = 84.5 x 8.5
or 8.5 x A + 8.5x B + 8.5 x C = 84.5 x 8.5 = 718.25
8.5 A + 5.28 x B + 96.0 x C = 1100
8.5 A + 8.50 x B + 8.5 x C = 718.25
3.22 × B + 87.5 × C = 318.75 Equation (5)
To eliminate B, multiply equation (4) by 3.22 and equation (5) by 36.5
3.22(35.5 × B – 2.5 × C) = 3.22 × 904.25(Equation 4)
36.5(-3.22 × B - 87.5 × C) = 35.5 × 318.75(Equation 5)
or 3.22 × 35.5 × B – 8.05 × C = 2911.685 —- Equation (6)
36.5 × 3.22 × B + 3193.75 C = 13933.875 —- (Equation (7)
3185.70 C = 16845.56
3185.70 C = 16845.56
C = 16845.56
————— = 5.28
3185.70
Quantity of skim milk powder required = 5.28
Substitute the value of C (= 5.28) in equation (4)
36.5 x B – 2.5 x 5.28 = 904.25
or 36.5 x B – 13.20 = 904.25
or 36.5 x B = 904.25 + 13.20
36.5 x B = 917.45
or B = 917.45
———— = 25.13
36.5
Quantity of Cream required = 25.13 Kg
Substitute the value of C (=5.28) & B (=25.13) in equation (1)
A + 25.13 + 5.28 = 84.5
or A = 84.5 – (25.13 + 5.28)
= 54.09
Quantity of Milk required = 54.09 Kg.
Combining the ingredients
All liquid ingredients (milk, cream, concentrated milk, syrup, etc.) are placed in the vat, and
the agitation and heating are started at once.
To facilitate operation with a fully liquid system, it is often necessary to dissolve some dry
ingredients.
If they are not liquefied first, dry ingredients, including skim or whole milk powder, dry
whey, dried eggs, cocoa, sugar, and stabiliser, are added while the liquid materials are being
agitated and before the temperature reaches 50°C.
Dry ingredients can be blended into the nonfat liquid materials with an emulsifying agitator
that is mounted inside the mix tank. More efficient blending is done with high shear mixers
or with “powder funnels.”
Pasteurization of ice cream mix
All liquid ingredients (milk; cream etc.) are placed in stainless steel tank provided
with a stirrer. The heating of liquid ingredients is started with stirring. The mix
ingredients are mixed thoroughly. The dry ingredients (skim-milk powder, sugar,
stabilizer etc.) are then added slowly with proper mixing. The heating of the mixture
continued up to 49-50°C while mixing the ingredients. If gelatin is used as stabilizer,
it is added to the liquid ingredients before heating started. If sodium alginate is used
as stabilizer, it should be added when the temperature of mix reaches 65°C or
above. It should never be added to cold mix. Proper pasteurization of all mixes is
compulsory because this process gives the following advantages:
a) Destroys all pathogenic or disease producing bacteria, thereby safe guarding
the health of the consumer:
b) Brings the ingredients of the mix in to solution and aids in blending.
c) Improves flavour.
d) Improves keeping quality.
e) Produces a more uniform product.
Proper pasteurization consists of rapidly heating the mix to a definite temperature,
holding it at that temperature for a definite period of time and then rapidly cooling to
below 5°C.
The recommended pasteurization temperature-time combination for ice cream mix
are as follows:
a) Batch method = 68.5°C for not less than 30 minutes
b) High temperature -Short time (HTST) Method = 80.0°C for not less than 20
seconds
The present trend is towards higher temperature processes like Ultra high temperature
for few seconds.
HOMOGENIZATION OF MIX
Homogenization of ice cream mix is essential. The main purpose is to make a
permanent and uniform suspension of the fat by reducing the size of the fat droplets
preferably of the size of not more than 2 microns in diameter. When mix is properly
homogenized the fat will not rise and form a cream layer. The ice cream mix is
usually homogenized at temperatures above 60°C. Use of higher temperatures in
homogenization process has the following advantages:
a) Results in less clumping of fat globules
b) Lower viscosity in mix
c) Reduces freezing time in batch ice cream freezers.
Two-stage homogenization of ice cream mix is more suitable than one stage
homogenization. In two stage homogenization a pressure of about 175 Kg/Sq. cm
to 205 Kg/Sq. cm in the first stage and 35 Kg/Sq. cm in the second stage gives
good results for average mix. It is preferable to homogenize ice cream mix at
pasteurization temperature. The advantages of homogenization of mix are:
a) Fat globule size is reduced and hence no cream layer formation.
b) Produces more uniform ice cream with a smooth texture.
c) Improves whipping ability.
d) Reduces ageing period.
e) Reduces the amount of stabilizer required in ice cream mix.
COOLING AND AGEING OF MIX
Cooling of the mix immediately after pasteurization and homogenization is essential.
The mix should be cooled to 4.0°C or below. Cooling is usually done using surface
coolers, tubular coolers or other type of heat exchangers. The temperatures below
4°C retard the growth of bacteria. Ageing refers to holding the ice cream mix at a
low temperature for a certain period of time before freezing. The ageing temperature
should not exceed 4.5°C. The ageing time under average commercial conditions
may be about 4 hour only. It may be increased depending upon the type of stabilizer
in the mix:
Following changes occur in the ice cream mix during ageing:
i) Fat is solidifies
ii) Stabilizer swells and combines with water.
iii) Viscosity increases.
Ageing of ice cream mix offers the following advantages:
i) Improves body and texture of ice cream.
ii) Improves whipping ability of mix.
iii) Increases maximum overrun.
iv) Increases melting resistance of mix.
FREEZING OF MIX
When the mix has been properly aged it is ready for next step, that is, freezing.
Freezing is one of the most important operations in the preparation of ice cream,
because, upon this depends the quality, palatability and yield of the finished product
The freezing process may be divided as follows into two parts:
a) The mix with colour and flavouring materials added is quickly frozen in the ice
cream freezer. During freezing, the mix is agitated to incorporate air in such a
way as to produce and control the formation of small ice crystals so necessary
to give smoothness in body and texture, palatability and satisfactory overrun in
the ice cream.
b) The mix partially frozen to a certain consistency in the ice cream freezer is
drawn out from freezer into packages and quickly transferred to cold storage
rooms where the freezing and hardening process is completed without agitation.
Fast freezing is essential for smooth textured ice cream because ice crystals
that are formed quickly are smaller than those formed slowly. Therefore it is,
desirable to freeze and draw out from the freezer in a short time as possible. A
continuous freezer accomplishes this in few seconds, while batch freezer takes
6 to 10 minutes or more time depending upon several factors. Also, since
freezing continues after ice cream is placed in the hardening rooms, the ice
crystals formed during the hardening period are larger because they form more
slowly than in the freezer. For this reason, it is desirable to freeze the ice cream
as stiff as possible and yet have it liquid enough to draw out of the freezer.
i. Types of Ice Cream Freezers
The equipment used for partial freezing of ice cream mix is called ice cream freezer.
Three types of ice cream freezer are identified
i) Batch freezer : It consists of a refrigerated drum or cylinder provided with a
dasher and scrapper fitted in to it. An electric motor drive turns the dasher
assembly within the cylinder. The scrapper removes the frozen ice cream from
the refrigerated surface and dasher whips the ice cream to introduce air into it.
Freezer is also filled with a hopper to introduce fruits and flavour. Commercial
freezers vary from 5 litres to 50 litres capacity.The batch freezer consists of freezing chamber
and a dasher. The dasher assembly comprises of two parts, viz., the scrapper blades and the
beater.
The dasher performs the following functions:
●​ Aids in transmission of refrigeration by keeping mix in continuous contact with
freezer walls.
●​ Scraps freezer walls free from ice crystal.
●​ Incorporates air.
●​ Pushes mix continuously forward (this helps to unload ice cream from freezer).
●​ The temperature of the refrigerant circulating in the freezer should be below
– 23°C to get rapid formation of ice crystals.
Freezing procedure in the batch freezer: The mix is run into the freezer, the
dasher started and then the refrigerant is turned on. This sequence must be observed
at all times to avoid damage to the machine. The flavouring and colouring materials
are added to the mix. The total volume of the mix, flavour and colour should be
about half the total volume of the freezing chamber. To avoid variation from batch to
batch, each batch of mix must be measured carefully before putting in to the freezer.
The freezing operation must be closely watched to know the correct time to shut-off
refrigeration. This comes mostly by experience of the operator. If the refrigerant is
allowed to run for a longer period the following problems may arise.
●​ Difficulty in obtaining the desired overrun
●​ Mix becomes stiff
●​ Whipping becomes difficult
After refrigerant is shut-off, the freezer without certain limits continue to operate,
incorporate more air, freezing more of water until the product attains both the desired
overrun and desired consistency. The ice cream from the freezer should be emptied
into the container/package as rapidly as possible to avoid fluctuations in overrun in
packages. When the ice cream is drawn from the freezer it should be stiff enough to
hold its shape and yet soft enough to loose its shape within a short time.
Cleaning of batch freezer: After the last batch of ice cream is drawn, the freezer
is first flushed with water. The rinse water should not be very hot. During rinsing
operation the dasher should be turned only a few revolutions. The dasher and other
removable parts should be removed to a sink and thoroughly scrubbed with a hot
(about 50°C) detergent solution, rinsed, sanitized and stored where they may dry.
The freezer chamber is also scrubbed with hot detergent solution, rinsed and left
open to dry.
ii) Continuous Freezer: The process consists of continually feeding into end of
the freezing chamber a metered amount of ice cream mix and air. As the mixture
passes through the freezing chamber it is agitated, partially frozen and then
discharged in a continuous stream of about same consistency usually obtained
from a batch freezer.
The continuous freezers are of two types: One type has two pumps at the back
of the freezer barrel. One pump pulls mix from the supply tank and pumps into
second pump. The second pump operates at a speed almost twice that of the
first pump. This has the effect of creating a partial vacuum between the two
pumps. A valve device in the piping between the pumps allows air to be sucked
in. The amount of air incorporated, in the mix can be regulated by a control
valve. The mix and the air both are pumped into the freezer’s barrel by the
second pump. As mix freezes, semi-frozen ice cream is forced out of the front
end.
The second type of continuous freezer operates in a similar fashion. However
the two pumps are at the front end. One pump pushes the mix into the back
end of the freezer and the other helps to pull the semi frozen ice cream from the
freezer barrel. There is a separate pump that forces air directly into the freezer
barrel.
In the continuous freezer, the mix is continuously pumped into the machine and
the frozen product is continuously discharged from the machine. Initially, the
amount of air introduced is regulated to give the desired overrun in the ice
cream. The temperature of refrigerant on the freezing chamber is adjusted to
give the desired consistency when the product leaves the machine.
Cleaning of continuous freezer: Method of cleaning continuous freezer is
similar to the methods of cleaning most of the dairy equipments. Remove all
pipelines, which carry ice cream mix to the freezer. Remove the front of freezer
unit and pull out the freezer dasher. Rinse all parts of machine, which come in
contact with ice cream mix, with warm water (35°C-40°C). Flush the freezing
tube with cold water followed by warm water. Thoroughly wash and clean all
parts of freezer with hot detergent solution. Rinse with hot water to remove all
traces of detergent. Finally rinse with scalding hot water and allow it to dry.
iii) Soft serve freezer: This is similar to batch the freezer in construction and
operation with lesser capacity. The overrun obtained in this type of freezer is
less than that is obtained in batch freezer. Time taken for freezing ice cream in
the freezer will dependent on many factors. Some factors are mechanical while
some others due to the property of ice cream mix.
ii. Factors Influencing Freezing
These factors may be mechanical factors and the factors related with the properties
of the mix as listed below.
A) Mechanical factors:
●​ Type and make of ice cream freezer.
●​ Condition of freezer wall and blades.
●​ Speed of dasher.
●​ Temperature of refrigerant.
●​ Velocity of refrigerant passing around freezing chamber.
●​ Overrun desired.
●​ Temperature at which ice cream is drawn.
●​ Rate of unloading of freezer.
B) Characteristics of mix or property of mix:
●​ Composition of mix.
●​ Freezing point of mix.
●​ Acidity content of mix.
●​ Kind of ingredients, particularly those carrying fat.
●​ Methods of processing mix.
●​ Kind and amount of flavouring materials used.
Freezing time and temperature: The freezing time and temperature of different
types of ice cream freezers are
Changes occurring during freezing: The functions of the freezing process are
listed below.
To freeze a portion of water of the mix
To incorporate air into the mix.
This involves:
Lowering of the temperature of the mix from ageing temperature to the freezing
point.
Freezing a portion of water of the mix.
In-corporation of air into the mix.
Cooling the ice cream from the temperature it is drawn from the freezer to
hardening room temperature.
The temperature of the mix in the freezer drops rapidly while the sensible heat is
being removed and before the ice crystals are formed. This process takes less than
a minute or two. Rapid agitation of the mix reduces the viscosity of the mix. Also
rapid agitation hastens incorporation of air into the mix. When freezing point is
reached, water in the mix starts freezing and ice crystals are formed. As part of
water is converted into ice crystals, the concentration of sugar in the remaining water
increases causing the freezing point of the mix to be lowered. So the temperature of
the mix must be lowered before some more ice crystals could be formed. Thus, the
freezing point is continuously being lowered by the formation of more ice crystals
while temperature drops. The first phase of the freezing process accounts for freezing
33 to 67% of water depending on the drawing temperature. The hardening process
then may account for the freezing of remaining portion of water up to 90-95%.
During this period when the temperature of ice cream mix is being lowered and ice
crystals are being formed, ingredients such as acid fruit juices fruits and nuts may be
added without any danger of coagulation of the mix. During this process more air is
also incorporated into the mix due to agitation. Freezing process gives a definite
texture to the ice cream. The texture of ice cream depends on the size and no of air
cells and ice crystals and unfrozen materials in the ice cream. Air cells are dispersed
in a continuous liquid phase with embedded ice crystals. The liquid phase contains
solidified fat particles, milk proteins, in-soluble salts, stabilizers and some lactose
crystal. Sugar, part of lactose and soluble salts are in true solution.
OVERRUN IN ICE CREAM
Overrun is usually defined as the volume of ice cream obtained in excess of the
volume of the mix. It is usually expressed as “percent overrun”. The increased
volume is composed mainly of air incorporated during the freezing process. The
amount of air which should be incorporated depends upon the composition of the
mix and the way it is processed and is regulated so as to give that percent overrun
which will give proper body, texture and palatability to the ice cream. Too much air
will produce a snowy fluffy ice cream while too less air on the other hand will lead to
soggy, heavy ice cream.
i) How to obtain and control overrun: The following factors need to be
considered in determining the amount of overrun in ice cream.
●​ Legal regulation enforced in the market area.
●​ Total solids content of the ice cream mix.
●​ Type of ice cream to be made (fruit/nut ice cream etc.)
●​ Selling price of ice cream.
●​ Type of packages.
The overrun attainable at the freezer depends upon the following points:
●​ Type of ingredients used in the mix.
●​ Sharpness of scrapper blades.
●​ Speed of dasher.
●​ Volume of refrigerant passing over freezing chamber.
●​ Temperature of refrigerant
The use of proper overrun tester will ensure uniform overrun. The control of overrun
is very important and should be maintained as nearly constant as possible from
batch to batch.
ii) The percent overrun: The percent overrun in different types of ice creams is

iii) Failure to obtain the desired overrun: Due to the following factors one fails
to obtain overrun in ice cream
Longer time to obtain overrun.
Too high drawing temperature.
Very soft ice cream.
Tendency to form ice cream with coarse texture because of large is crystal
formed.
iv) Method of calculating percent overrun: There are following two methods
by which the percent overrun can be calculated.

Defects and causes

High quality ingredients are required in the production of high quality ice cream. Adherence
to formulation, industry processing standards and proper storage requirements are also
critical. Incorporation of inferior dairy ingredients, sweeteners, or other ingredients always
will result in a substandard product. Some of the defects likely to be found in ice cream are
discussed below.
Flavour Defects
Flavour is the most important sensory attribute in judging and grading of ice cream and
frozen desserts. Even a minor flavour defect in ice cream will affect its acceptability by the
consumer. Some of the prominent flavour defects are discussed in this chapter along with
their causes and prevention.
22.2.1. High flavor
This flavor condition, when it occurs, is best recognized when the sample is first placed into
the mouth.
The intensity of the flavoring seems so striking or sharp that the desired, pleasant flavor blend
is not achieved due to the harsh tones imparted by the flavoring level observed in the product.
Ice cream that is too highly or excessively flavored is not severely criticized as a rule,
especially if the quality of the flavoring used is high. An associative "ethanol-like‘‘ note may
be present.
22.2.2. Too sweet
An ice cream that is observed to be excessively sweet tends to exhibit a candy-like taste
sensation; this
defect is readily noted upon the first stages of tasting. Too much sugar (or other form of
sweetener) tends
to interfere with the overall desirable blend of flavor(s). Another unfortunate characteristic of
a given ice
cream that is perceived as being too sweet is a general lack of refreshing property.
22.2.3. Lacks sweetness
An ice cream that lacks sweetness is readily noted upon tasting; the product simply manifests
a distinct flat
or bland taste. The desired or anticipated blend of flavor is missing. An adequate amount of
sweetener is
required to bring out the full flavor ‗‗bloom‘‘ in a given flavor, whether it is vanilla, fruit, or
chocolate ice
cream. Since preferences for the desired level of sweetness vary among individuals, the
product is not
severely criticized for lacking sweetness, within reasonable limits, if this is the only flavor
defect
encountered. However, a severe deficiency in sweetener solids may give rise to readily
evident defects in
body and texture or mouth feel.
22.2.4. Syrupy /Malty flavour
This sweetener off-flavor is still commonly encountered in certain forms of corn syrups and
corn syrup
solids; hence ‗‗syrup flavor‘‘ is the common descriptor for this characteristic defect.
Frequently
encountered descriptions for syrup flavor might be malty,caramel-like, molasses-like or
similar to low
levels of burnt sugar. Some evaluators distinguish syrup flavor from high sweetness by the
‗‗catch‘‘experienced in the throat, similar to the feeling after a dose of cough syrup.Certain
forms or
sources of corn syrup solids, corn syrup, and some liquid sugar blends (with excessive levels
of corn
syrup), when used in ice cream in high proportion to sucrose, may convey a slight to distinct
malty or
caramel-like off-flavor.
22.2.5. Lacks fine flavour
This criticism is generally used to describe an ice cream that is basically ‗‗good‘‘ or ‗‗very
good,‘‘ but for
some less than clear reason, it seems to just barely fall short of being ‗‗perfect‘‘ or ‗‗ideal.‘‘
experienced ice
cream judges are able to recognize the desirable, delicate, balanced flavor notes of a high
quality flavor.
The novice judge should remember that ‗‗lacks fine flavor‘‘ is not readily described in more
definitive or
specific terms.
22.2.6. Lacks flavouring
An ice cream with this defect is often criticized as flat, bland, or deficient in the amount of
added
flavoring. Even though the ice cream may be pleasantly sweet and free from any dairy
ingredient off-
flavor, it seems to lack the characteristic delicate ‗‗bouquet‘‘ of excellent vanilla; the desired
intensity is
missing. The obvious cause of this defect is failure to use sufficient quantities of flavoring.
However, there
are instances when certain ingredients mask (or hide) the vanilla flavor, thus invoking the
‗‗lacks flavor‘‘
criticism, even though the added quantity of flavoring seemed adequate to the manufacture.
22.2.7. Acid (Sour)
An acid or sour off-flavor in frozen dairy desserts may be distinguished from other
off-flavors by a
sudden, tingly, taste sensation (on the tip or top of the tongue), plus an associated ‗‗clean and
refreshing‘‘
mouth feel. This flavor defect may be caused by the use of acid whey in the ice cream mix.
The off-flavor
may also result from uncontrolled bacterial activity at elevated temperature; other bacterial
off-flavors
may also be present. In such cases, the flavor defect(s) may be more appropriately described
as a
combination acid (sour) and psychrotrophic bacteria-caused off-flavor (unclean, fruity, or
putrid).