Golden Ruler's of Penmai
- Sep 3, 2012
Normally, we drink cow's milk or buffalo's milk. So for further clarification it can be added that the secretion obtained within 15 days before and 10 days calving, or such longer period as may be necessary to render the secretion colostrum's free, is considered milk.
Constituents of Milk
Milk has a very complex composition. Its constituents are dispersed in an aqueous solution. The fat is present in emulsion. Milk constituents are mainly divided into three parts: Water, Fat and Solid-Not-Fat (SNF). The fat and SNF are together called total solids. If fat is removed from the milk, the remaining is known as milk serum.
The water present in milk is same as normal water. The function of water in milk is to hold the solids of the milk partly in solution and partly in suspension.
The fat or butter-fat in milk exists as an emulsion. When a droplet of milk is examined under a microscope, the fat globules are visible in the form of spheres. The size of fat globules vary from 0.1 to 20 microns, average 3 microns. It is the lightest constituent of milk, so when heated, the cream rises to the top of milk to form a layer.
The fat globule is surrounded by a thin film of protein and lecithin. The membrane is important in keeping the fat from becoming a free oil when it is heated. The membrane may also protect the fat against the action of enzymes (lipase), as lipase causes rancidity in butter-fat. the size and arrangement of globules affect the creaming ability of milk, the viscosity of cream, the whipping ability of cream and the churning of cream to butter.
Fats are the mixtures of triglycerides of certain fatty acids. Milk fat contains 19 or more fatty acids. These fatty acids may be classified on a number of different bases - soluble and insoluble, volatile and non volatile, saturated and unsaturated.
Milk fat is is a very rich source of energy and is also a good source of vitamins A and D. The composition of fat is affected by many factors such as feed, stage of lactation and breed.
The Three principal classes of proteins in milk are casein, lactalbumin and lactoglobulin. The casein accounts for 80% of the total protein content. Lactalbumin and and lactoglobulin together known as whey proteins and are 20%.
A. Casein: -
This protein is found only in milk. It exists in milk with calcium so it is known as calcium caseinate. It is present in milk in a finely divided suspension, called 'colloidal' dispersion. The casein is precipitated by acids ( when the milk sours or acid added to it ).
As casein is a protein, it helps in muscle building, and provides nutrition to our body.
B. Whey Proteins: -
The proteins, lactalbumin and lactoglobulin are present in small amounts, dispersed in milk. Usually the first milk secreted after calving (colostrum) contains sixteen times more whey proteins than normal milk. This amount decreases rapidly to normal amount during first few milking. Whey proteins serve body in the same way as caseins.
Lactose is a carbohydrate found only in milk, and is synthesised in mammary glands. Lactose is easily changed to lactic acid by bacterial action which causes the milk to taste sour. In some dairy products like curd, butter, cheese, butter milk, the flavour is due to this acid fermentation.
Lactose serves body as a source of energy. Lactose has such nutritive properties which are not possessed by other carbohydrates/sugars.
Vitamins and Minerals
Milk contains a number of important vitamins. Though they are present in milk in small quantities, are vital for our health and growth. There are two types of vitamins present in milk.
Fat soluble vitamins - Vitamin A, D, E and K
Water soluble vitamins - Vitamin B complex (B1, B2, B6, niacin, folic acid, biotin) and Vitamin C (ascorbic acid).
The minerals (or salts) present in milk are calcium, potassium, phosphorus, magnesium, chlorides. Milk minerals are very essentials for the young, they help to build bones and growth of teeth.
Other Minor Constituents of milk are pigments, cholesterol, enzymes, phospholipids and nitrogenous substances.
Average Composition of Milk
Cow Milk (%)
Water - 86.36
Total Solids - 13.64 (Fat - 4.9, SNF - 8.74)
Proteins - 3.4
Lactose - 4.6
Ash - 0.74
Buffalo Milk (%)
Water - 83.22
Total Solids - 16.78 (Fat - 7.3, SNF - 9.48)
Proteins - 3.8
Lactose - 4.9
Ash - 0.78