Several types of fluid milk are marketed in many countries. These include
Homogenised milk: In homogenised milk, the fat globules are broken up mechanically to less than 1 micron in diameter so that fat does not rise to the surface to form a cream layer. The process consists of forcing milk heated to about 57 to 60 0 C (135-140 0 F) through a very small orifice at high pressure. All homogenised milk should be pasteurized after homogenisation to destroy the enzyme-lipase which otherwise would cause the milk to become unfit for human consumption within a few hours due to the development of bitterness and rancidity. One disadvantage of homogenised milk is that milk fat cannot be separated as cream in a cream separator. The fat in homogenised milk is more readily digested by infants than that from ordinary milk.
Standardised Milk In standardised milk, the fat content is maintained at 4.5 per cent and S.N.F. at 8.5 per cent. It is prepared from the mixture of buffalo milk and skim milk.
Toned Milk Toned milk is prepared by mixing reconstituted from skim milk powder with buffalo milk containing 7.0 per cent fat. The fat content of the toned milk should not be less than 3 per cent and S.N.F. 8.5 per cent.
Double toned milk This is prepared by admixture of cow's or buffalo's milk or both with fresh skimmed milk or by admixture with skim milk reconstituted from skim milk powder or by partial removal or addition of milk to skim milk. It should be pasteurised and show negative phosphatase test. Its fat content should be less than 1.5 per cent and S.N.F. not less than 9 per cent.
Recombined Milk Recombined milk is a homogenised product prepared from milk fat, non-fat milk solids and water. It should be pasteurised and show a negative phosphatase test. Its fat content should be less than 3 per cent and S.N.F. 8.5 per cent.
Filled milk Filled milk is a homogenised product prepared from refined vegetable oil and non-fat milk solids and water. Its fat content should not be less than 3 per cent and S.N.F. 8.5 per cent.
Sterilised milk Standardised cow's or buffalo's milk is sterilised in bottles by heating continuously to a temperature of 115oC for 15 minutes to ensure destruction of all micro-organisms and preservation at room temperature for not less than 85 days from the date of manufacture. It shall be sold only in the container, in which milk was sterilised.
Ultra high temperature (UTH) processed milk Milk is heated at temperatures higher than those used for pasteurisation, 138°-150°C for 2-6 seconds. Then, under sterile conditions it is packaged into presterilized containers, which are aseptically sealed so that spoilage organisms cannot enter. Hydrogen peroxide may be used to sterilise the milk packing materials. UHT milk can be stored unrefrigerated for at least 3 months.
UHT milk has cooked flavour due to denaturation of the whey protein β lactoglobulin. Off flavours develop due to chemical and enzymatic activity. The addition of flavourings to milk masks off flavour.
Flavoured milk Flavoured milk may contain cardamom, pista, banana, strawberry, chocolate, coffee or any other edible flavour, edible food colour and cane sugar. It is either pasteurised or sterilised. Shelf life can be high if it is sterilised.
Research has shown that carbon dioxide when added to milk creates a unique sensation in the mouth that actually makes milk more thirst quenching. It is also showed that carbon dioxide could extend the shelf life of dairy products by displacing some of the oxygen needed for spoilage bacteria to grow. A non-fat milk-based drink contains the same nutrition as skim milk. It is designed to appeal to kids through the addition of interesting flavours and a bit of carbonation. It is being commercially produced.
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