Milk, according to Academician Pavlov, is a wonderful food presented to us by nature, necessary for a person from the first months of life to the last days. People have been drinking milk for more than five millennia and know that it contains all the substances necessary for the body: proteins, carbohydrates, enzymes, fats, vitamins, hormones and mineral salts, and these perfectly balanced components are completely and easily digested.
Every person who uses milk wants to be sure of its quality. Among the many indicators characterizing its composition, one of the main ones is a test that determines the density of milk. Not everyone knows why this indicator is needed, what its optimal digital value should be, and what, in fact, can be learned from it about the quality of milk and dairy products.
Determination of density according to accepted methods allows to detect falsification of milk. Normal density corresponds to the limits from 1.026 to 1.032 g / cm3 and depends on the breed of cows, as well as the conditions of their maintenance, feeding and other circumstances.
The density of milk is the higher, the more sugar, protein and minerals it contains, and the lower the more fat. Too low a density indicates that milk is diluted with water, and a high density indicates the addition of skim milk or cream. It is characteristic that if fat is removed from milk and the same amount of water is added, then the density does not change, and such falsification can be detected by determining the amount of fat in milk and comparing the indicators. Thus, the density of milk is the main indicator of its naturalness.
The organoleptic and physico-chemical properties of milk are guided by the determination of its naturalness and suitability as raw materials for industrial processing.
Indicators such as acidity, purity, and milk density are checked daily upon acceptance.
Of course, fresh, freshly milked milk is the most complete in its qualities. For some time, it contains special substances that can inhibit the reproduction and even cause the death of bacteria falling into it. The duration of the bactericidal properties of milk depends on its purity and storage temperature. But milk is a perishable product, therefore, to increase the shelf life, it is processed and processed.
At dairies, milk processing is carried out under the control of a special sanitary service, which, among other things, controls the density of all dairy products. Determining the density of pasty and solid dairy products is much more difficult than liquid, therefore, special devices are used for monitoring.
The density of all dairy products depends on their composition. For example, for skimmed processed milk, it is higher than for raw milk. The density of the cream is higher, the lower the fat content. Dry milk, in addition to the actual density, is also controlled by bulk density . The density of a product such as butter depends not only on the non-fat dry residue and the amount of moisture, but also on the air it contains. This indicator is determined by the flotation method, which is considered approximate, but quite sufficient for practical purposes.
Milk density can be checked at home. If you drop a small amount of it into a vessel with water, then drops of undiluted milk will immediately fall to the bottom of the container and dissolve, and if water is added to it, then the drops will instantly spread over the surface.
You can also mix milk and alcohol (1: 2) and pour on a platter. If the milk is whole, flakes will immediately appear, when it is diluted with water and has a reduced density, then the flakes will not form for a long time.
Thus, the density indicator is the most important criterion for determining the naturalness and quality of milk.