What is milk?

Milk is a whitish secretion, generally secreted by females (in a few species by males), of mammals; composed mainly of water, proteins, sugars and fats.
Milk has all three forms of physical solution:
Dissolution: in which the minerals, vitamins and carbohydrates are dissolved in the water.
Suspension: it is the phase in which the proteins are found, and that with the appropriate substances they can coagulate and separate from the water.
Emulsion: the fat in water, given the difference in densities, is divided into smaller droplets forming an emulsion.
The human being, in addition to that of his own species, consumes milk from other animals, among which cows, camels, sheep, goats, donkeys, mares and buffaloes stand out.
The composition of milk varies between each species. Based on cow's milk, each liter contains 900 grams of water, 130 grams of protein, 35 to 40 grams of fat and 60 to 65 grams of lactose and 3 to 5 grams of minerals and vitamins.
Nutritionally, milk provides proteins, fats, vitamins A, B, D and E, calcium and the carbohydrate of milk, lactose or milk sugar.

The consumption of milk has existed since the domestication of animals, about 12,000 years ago. Some time later, approximately 5,000 years ago, the methods to obtain the derivatives of milk emerged: Cheese, Cream and Butter.
Butter is obtained by repeatedly tapping the milk with a paddle, which causes the fat particles to fuse, which are left with a slight remainder of solids.
Cream is the combination of milk solids together with fats, which, due to their lower density, separate and remain on the surface of the milk, taking on a thicker and greasy consistency than the rest of the liquid.
Cheese is made from the coagulation of casein, by the action of chemical substances or animals, known as rennet; the excess liquid is called serum. When whey is boiled it is still possible to coagulate other dissolved proteins, mainly albumin and traces of casein, producing cream cheese or cottage cheese.