Objectives:
1. To know the method of preparation of Ice-cream by hand freezer on home laboratory scale.
2. To evaluate the quality of Ice-cream.
3. To estimate the over run in Ice-cream preparation.
Relevant information:
Ice cream may be defined as a frozen dairy product made by suitable blending and processing of cream and other milk product together with sugar and flavour, with or without stabilizer or colour and with the incorporation of air during the freezing process. According to the PFA. Rules (1976). Ice cream is the frozen product obtained from cow or buffalo milk or a combination there of or from cream and / or other milk products with or without the addition of canesugar, eggs, fruit juices, preserved fruits, nuts, chocolate, edible flavours and permitted food colour. The product should contain not less than 10 % milk fat 3.5 % protein and 36% total solids.
There are different types of frozen food products such as
(I) ice-cream
(II) Ice milk
(III) Milk sherbet
(IV) Fruit ice and
(V) Water Ice. Some of these frozen products do not contain any constituents of milk. But their methods of preparation are quite similar to frozen milk products.
Constituents in Ice-cream:
1. Milk fat:
It enriches and allows the Ice-cream to give its full rich creamy flavour.
2. Milk solids:
Not fat: consists of milk proteins, milk sugar and mineral matter-improve of body and texture.
3. Sugar:
To increase the acceptability of Ice-cream.
4. Emulsifiers:
Mainly improve the texture and provide a uniform whipping quality of the mixture.
5. Stabilizers:
Used to prevent the formation of large Ice-crystals especially during Storage.
6. Flavour:
Increases the acceptability of Ice-cream induces its aesthetic appeal.
The non milk ingredients like colouring material, flavours, fruits, sugar, eggs stabilizers etc. are not subjected to heat treatment during preparation and hence may act as a source of disease infection, food poisoning (typhoid fever, dysentery) and hence quality ingredients should be used.
Precautions:
1. A sour cream should never be used in Ice – cream
2. Milk and milk products (Constituents) should be free from off flavours; otherwise these are intensified in the product.
3. Excessive addition of fat and sugar should be avoided as they develop defects in the products.
4. Proper level of stabilizer should be used to possess resistance to melt down.
Material required:
Milk, Cream, stabilizer (edible gelatin, custard, sodium, alginate, guar-gum. Gum Arabic).
Essence. Ice, salt, sugar, colour.
Apparatus:
House holds Ice-cream freezer, Ice-cream cups, and spoon.
Hand freezer:
Domestic hand freezer is a wooden barrel of various capacities with a central stainless steel or other metal cylinder. The cylinder is fitted inside with a scrapper made of wooden blades. The cylinder and inside scrapper may be resolved by means of a handle through pinion arrangement. The freezing is brought by a suitable freezing mixture (5 parts of Ice + 1 part of common salt.) which maintain the temperature of 21-23 0 F.
Procedure:
1. Preparation of balance mix, weight all ingredients separately in the proportion i.e. whole milk 60 (percent) 20 percent cream, 5 percent skim milk powder, 15 percent sugar, 0.5 percent stabilizer.
2. Flavours & colours: As per requirement.
3. Put into the vat the liquid ingredients first.
4. Start heating and then add dry ingredients.
5. Gelatin stabilizer if used should be liquefied and then added in the mixture. Colour and flavour are added just before running the mixture in to the freezer.
6. Pasteurize the mixture to 145 0 F for 30 min and cool and 32 0 F. Then the mixture is aged at this temperature for 4 hrs. After a going put the mixture in the ice-cream pat (cylinder) up to ½ of the capacity of the chamber of (freezer).
7. Pack the freezer about half full of ice-crystals and then alternate layers of salt and ice are added until cylinder is covered.
8. The scrapper is the n turned slowly until; it is just beginning to turn hard after which it should be turned faster to whip then necessary air into the ice-cream.
9. After Ice-cream is half frozen, it should be packed with ice and left for hardening in the refrigerator.
10. Find out the volume of Ice-cream mix and Ice-cream by measuring height and diameter.
Calculations:
Over run in Ice-cream the amount of air whipped into the ice-cream is commonly expressed as per cent over run. Over run is the increased in volume of the ice-cream over the volume of the mix expressed as per cent of the volume of mixture.
Volume of ice-cream – volume of mixture
Percent over run = —————————————————————— x 100
Volume of mixture
