TYPES OF PROCESSED MILK
Raw milk is processed into the following types of milk.
1. Skim Milk:
Skim milk is whole milk from which fat has been removed by a cream separator. The quantity of fat is usually 0.05 to 0.1 percent. It contains all other milk nutrients, except Vitamin A and D, but can be fortified by the addition of these vitamins.
2. Toned Milk :
Toned milk is prepared by using milk reconstituted from skim milk powder. Skimmed milk is prepared by removing fat from milk in a cream separator.
The skimmed milk is then mechanically dried to give skim milk powder. It is mixed with buffalo milk containing 7 percent fat. The fat content of toned milk should be less than 3 percent.
3. Standardised Milk:
In standardised milk the fat content is maintained at 4.5 percent and soluble non-fat is 8.5 percent. It is prepared from a mixture of buffalo milk and skim milk.
4. Homogenised Milk:
Homogenisation is a mechanical process that reduces the size of fat globules by forcing milk through small apertures under pressure and velocity.
When milk is homogenised, the average size of the globule will be 2 micrometers. The decrease in the size of fat globules increases their number and surface area.
The newly formed fat droplets brings about stabilisation of the milk emulsion and thus prevents rising of the cream. Homogenised milk has a creamier texture, bland flavour and whiter appearance.
5. Evaporated Milk:
It is made by evaporating more than half the water from milk under vacuum, at a temperature of 74 o C - 77 o C. It is then fortified with vitamin D, homogenised and filled into cans
and sterilized at a temperature of 118 o C for 15 minutes and cooled. The treatment employed lends a brown colour and characteristic flavour owing to the reaction between sugar and protein.
6. Condensed Milk:
It is obtained when whole milk is concentrated to about one-third of its original volume and has about 15 percent sugar added to it. The preparation of condensed milk involves (i) filtration and pasteurization of milk, (ii) preheating and evaporation, (iii) addition of sterilised sugar syrup, (iv) homogenisation.
7. Flavoured Milk : It is the milk prepared by the addition of flavour such as rose, pista, badam, cardamom etc. to pasteurised whole milk.
8. Milk Powder: Milk powder is prepared by dehydrating whole milk in drum driers or spray driers. In the case of drum or roller drying, the milk is filtered, pasteurized, homogenised and then fed into roller driers which are internally heated with steam.
The dried milk is obtained as a thin sheet and is powdered. In spray drying, the homogenised milk is blown as a fine spray into a pre-heated vacuum chamber resulting in fine dry powder. The milk powder is collected, cooled and packed.