Preparation of ice-cream

Prof.S.Biswas & Dr.G.Patra

Dept. of LPT
F/O-VAS, WBUAFS
Definition:

Ice cream may be defined as a frozen dairy product made

by suitable blending and processing of cream and other dairy
products together with sugar and flavour, with or without
stabilizers or colour, and with the incorporation of air during the
freezing process.
 According to the PFA rules (1976) ice cream contain

1. Permitted stabilizers and emulsifiers not exceeding 0.5

per cent by weight.

2. The mixture must be suitably heated before freezing.

3. The product should contain not less than 10%milk fat,

3.5% protein, and 36% total solids.
 Classification
Plain: Ice cream in which the colour and flavouring ingredients. Example: vanilla and coffee
ice creams.
Chocolate: Ice cream flavoured with cocoa or chocolate.
Fruit: Ice cream containing fruits with or without additional fruit flavouring or colour. Fruits
such as strawberry, apricot, pineapple, mango, banana, etc.,
Nut: Ice cream containing nuts, such as almonds, pistachio, walnuts, cashew nut, etc.
Milk ices or lollies: According to the PFA rules (1976) these refers to the frozen product
obtained from the milk or skim milk or milk products with or without the addition of cane
sugar, eggs, fruits, nuts, chocolate, edible flavours, and permitted food colours
Ices: Made of fruit juices sugar and stabilizers with or without additional fruit acid, colour,
flavouring, or water, and frozen to the consistency of ice cream.
Sherbet: made of juices, sugar, stabilizers and milk products. It is similar to an ice except that
milk, either whole, skim, condensed or powdered, or ice cream mix.
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.
Novelties: Novelty ice cream or frozen is an especially shaped and usually low priced
package containing an individual serving.
Soft ice cream: Sold as drawn from the freezer without hardening.
 Composition
Sr. No Characteristics Requirements

1. weight (g./litre) min. 525

2 Total solids(%wt .min) 36.0

3. Milk fat (% wt. Min.) 10.0 (Tentative)

4. Acidity (% lactic acid max.) 0.25

5. Sucrose (%wt. Max.) 15.0

6. Stabilizers/emulsifiers(%wt. Max) 0.5

7. Standard plate counts (per g.) Not more than 2,50,000

8. Coliform count (per g.) Not more than 90

9. Phosphatase test. Negative.

 Role of the constituents in ice cream
1. Milk fat: This is high in food value, but expensive. It enriches and
mellows the ice cream, giving it a full, rich, creamy flavour. The fat
also contributes to the body and melting resistance of ice cream while
producing a smoothness of texture.

2. Milk solids not fat: They add very little to the smell, but improve its
body and texture, however milk sugar adds to the sweet taste. The milk
proteins help to make ice cream more compact and smooth

3. Sugar: The main function of sugar is to increase the acceptability of

ice cream. The desired sweetening effect is only produced by sucrose.

4. Stabilizers: These are used to prevent the formation of objectionable

large ice crystals in ice cream, especially during storage.

5. Emulsifiers: These are used mainly to improve upon and provide a

uniform whipping quality of the mixture.
 Flow Diagram of Manufacture
Selection of Ingredients

Figuring the mix

Mixing Ice cream mix

(SMP, Cream, Sugar, Stabilizer, Emulsifier)

Homogenization of mix (1st stage-2500 psi & 2nd stage 500 psi)

Pasteurization the mix (68oC for 30 min)

Cooling (15oC)

Ageing of mix (4oC/3-4 hrs.)

Freezing the mix (-4 to -5 oC)

Packaging of ice-cream

Hardening and storage of ice-cream (-23 to -29oC)

 Selection of ingredients

Ice cream ingredients may be grouped into:

1. Dairy ingredients.

2. Non dairy ingredients.

 1. Dairy ingredients
Source of fat:
1. Sweet cream
2. Frozen cream
3. Plastic cream
4. Unsalted butter
5. Butter oil.
Source of milk-solids- not fat:
1. Skim milk
2. Skim milk powder
3. Condensed skim milk
4. Sweet cream buttermilk.
Sources of both fat and solids not fat:
1. Whole milk.
2. Whole milk powder
3. Condensed whole milk
4. Evaporated milk.
 2. Non dairy ingredients
Sweetening agents:
1. Cane sugar or beet sugar. 2. Corn sugar (dextrose)
3. Corn syrup solids (dextrose +maltose ) 4. Corn syrup
5. Invert sugar (glucose +fructose) 6. Saccharin.
Stabilizers:
1. Gelatin-of animal 2. Sodium alginate
3. Guar gum –of Indian origin. 4. Carageenan
5. Agar agar 6. Carboxy methyl cellulose
7. Pectin
Emulsifiers: They are substances which help to form emulsions.
1. Glycerol Mono Stearate (GMS).
Flavours:
1. Vanilla-Chocolate 2. Strawberry
3. Pineapple 4 .Lemon
5. Banana 6. Mango
7. Orange .
Colour:
1. Yellow 2. Green
3. Pink.
Egg solids:
1. Egg yolk solids improve the whipping ability.
Fruits and nuts:
1. Apple 2. Banana
3. Mango 4. Pineapple
5. Grape 6. Almond
7. Pistachio 8. Cashew nut
9. Walnut 10. Groundnut.
 Stabilizers
Gelatin-of animal origin.
1. It was one of the first of the commercial stabilizers and still used.
2. It form a gel in the mix during the aging periods as well as
during the freezing process and contribute to the smoothness on
texture and firmness in body of the frozen product.
3. The amount of gelatin used depends on several factors such as
the source of gelatin whether from calf, pork skin or bone
materials.
4. Commonly gelatin is used at the rate of 0.25 to 0.5 %.

Sodium alginate – of vegetable origin.

1. The basic stabilizing principle ‘algin’ is extracted from ocean
kelp (seaweed) growing on the shores of California and in Japan.
2. This product improves whipping ability and leaves a slightly
cleaner flavour in the mouth.
 Figuring the mix
1. Knowledge of calculation of ice cream mix is helpful in properly
balancing the mix.
2. Establishing and maintaining a uniform quality that conforms to
legal standards.
3. Ice cream mix may be divided into two groups, namely simple
and complex.
4. Simple mixes require the least calculation and are made of
ingredients, each of which supplies one constituent.
5. Complex mixes are more difficult to calculate they include mixes
where at least, one constituent is obtained from two or more
products.
6. Complex mixes require the use of the Pearson’s square, algebraic
methods.
 Making the mix
1. All liquid ingredients are placed in a jacketed vat provided.

2. Dry ingredients, including skim milk powder, sugar, and

stabilizers are added before the temperature reaches 49 ºC.

3. Proper suspension to avoid lumpiness.

4. Stabilizer added after it is thoroughly mixed with equal volume of

sugar.

5. If butter, plastic cream, frozen cream, or other products are used,

they should be cut into small.

6. Colouring and flavouring materials are added when the mix is

frozen.
 Pasteurization of mix
The ISI specification for pasteurization temperature:
1. Batch system- 68.5ºC for not less than 30min.
2. HTST method - 80 ºC for not less than 25 sec.

Purpose:
1. It renders the mix completely free of pathogenic bacteria.
2. It dissolves and helps to blend the ingredients of the mix.
3. It improves flavour.
4. It improves keeping quality, and produces a more uniform
products
 Homogenization of mix
The main purpose of homogenization is to make a
permanent and uniform suspension of the fat by reducing the
size of the fat globules to a very small diameter, preferably not
more than 2 microns.
Advantages:
1. It prevents fat separation during ageing.
2. Produces more uniform ice cream with a smoother texture.
3. Improves whipping ability
4. Shortens ageing period.
5. Decreases the risk of churning occurring in the freezer.
6. The mix is usually homogenized at temperature from 63 to
77 ºC at pressure of 2500 to 3000 PSI with one valve.
 Cooling and ageing of mix
1. Cooling the mix immediately after homogenization to 0-5 ºC is
essential for 3 to 4 hours.
2. Ageing refers to holding the mix at a low temperature for a
definite time before freezing.
3. The ageing temperature should not exceed 5 ºC.
4. Sodium alginate which requires no ageing.

Ageing
1. Improves the body and texture of ice cream
2. Improves the whipping capacity
3. Increases maximum overrun
4. Increases melting resistance.
 Freezing the mix
1. The freezing process may be divided into two parts.

2. The mix with the proper amount of colour and flavouring

materials generally added at the freezer.

3. Quickly freezing and incorporate air in such away as to produce

and control the formation of small ice crystals.

4. Provide smoothness in body and texture, palatability and

satisfactory overrun in the finished product.

5. After freezing and packaging immediately transferred to cold

storage rooms where hardening is completed without agitation.
 Classification of freezers

1. Batch freezer
2. Continuous freezer
3. Soft serve freezer
 1. Batch freezer

1. The batch freezer consists mainly of a freezing chamber

and a dasher.
2. The dasher consists of two parts viz., scraper blades and
the beater.

The dasher performs the following functions:

1. Aids in transmission of refrigeration by keeping the mix in
continuous contact with freezer walls.
2. Scrape freezer walls free of ice crystals, beats in air.
3. Continually pushes mix forward, which is essential for
unloading the freezer.
 2. Continuous freezer
1. One pump pulls the mix from the supply tank and pumps it to
the second one.
2. The second pump operated at a speed approximately twice as
great as that of the first pump.
3. This has the effect of creating a partial vacuum between the
two pumps.
4. The valve device in the piping between the pumps allows for
air to be sucked in.
5. The amount of air incorporated can be regulated very
accurately.
6. The second pump pumps the mix and air into the freezer
barrel.
7. As the mix freezes, semi-frozen ice cream is forced out from
the front of the machine.
 3. Soft serve freezer

Batch and automatic continuous freezer of the direct

expansion type
 Overrun in ice cream
1. Overrun is usually defined as the volume of ice cream obtained in excess
of the volume of the mix.
2. It is usually expressed as a percentage.
3. This increased volume is composed mainly of the air incorporated during
the freezing process.
4. The amount of air incorporated depends on the composition of the mix
and the way it is processed.
5. Too much air will produce a snowy, fluffy, unpalatable ice cream while
too little, a soggy, heavy product.

The desirable overrun percentage in different ice creams is given below.

Product %OR.
Ice cream packaged 70-80
Ice-cream bulk 90-100
Softy ice cream 30-50.
 Packaging of ice cream

Ice cream packages are of two types

1. Multi service:

a. Tinned steel can

2. Single service:

a. Fibre board cartons coated with wax or polythene wax

blends.
b. Cups, stick, or bars.
 Hardening and storage of ice-cream

The freezing process is continued without agitation in the

hardening rooms until the temperature of the ice cream is reached
–18ºC or below.

The different hardening systems are

I) Hardening rooms -12 to –45 ºC.

ii) Hardening tunnels -34 to -45 ºC.
iii) Hardening cabinets -23 to -26 ºC.