Milk is the normal secretion of the mammary glands of all mammals. Its purpose is to nourish the young of the species.
The principal constituents of milk –water, fat, protein, milk sugar or lactose and the minerals.
Water
Water is the medium in which all the other components of milk are dissolved or suspended. Water content varies from 85.4% to 87% in different species of cows.
Protein
Casein is the major protein, in contrast to lactalbumins in human milk. The major milk proteins are casein, alpha-lactalbumins, beta-lactoglobulin and the relatively smaller amounts are contributed by milk, enzymes.
Fat
The cream portion of milk is primarily due to the presence of fat. This family occupies about 4% of the total milk space in cow milk. The major lipid content of cow’s milk is triglyceride, which makes up about 98% of milk fat. The other 2% of milk lipids consist of diglycerides, monoglycerides, cholesterol, phospholipids, free fatty acids, cerebrosides and gangliosides.
Carbohydrate
Milk contains unique sugar lactose. It is responsible for imparting sweetness to milk although it is onw0offth as sweet as sucrose.
Minerals
Average normal is considered to contain 0.70% ash and this amount represents a salt of about 0.90%. Mineral make-up f milk is crucial to the stability of the physicochemical equilibrium in milk.
Vitamin
Milk is a unique food having at least 10 to 11 vitamins present in different proportion. Milk contains both fat soluble (A, D, E and K) and soluble water soluble vitamins.
Age is not an important factor effecting the composition of milk although there appears to be tendency for the fat content to decrease with increasing age. However, the health of the cow may affect milk composition considerably.
The most important single factor governing the composition of cow’s milk is the breed of the cow.
The principal milk producing breeds are the Ayrshire, Brown Swiss, Guernsey, Holstein and Jersey.
Holstein generally produces the most milk, but Guernseys and Jerseys produce milk with the highest fat contents.
What are the main constituents of cow's milk?
