INторичное сырье обладает незначительной пищевой ценностью по количеству жиров, белков и сухих substances.

Skimmed milk and buttermilk are widely used. Buttermilk is eaten both in its natural form and in pasteurized and fermented. In addition, these products are used in the preparation of certain types of cottage cheese.

Whey is used to prepare drinks - milk kvass, whey drinks, etc. In addition, whey is used in the preparation of albumin curds and albumin-curd cheeses, milk sugar (refined, pharmacopoeial and raw).

Serum is an excellent skin care product. It is recommended to wipe the face in the morning with a cotton swab dipped in serum.

Natural and condensed whey is also used in baking. It contributes to the saturation of bread with soluble forms of proteins, essential amino acids, calcium and phosphorus salts. In addition, whey speeds up the dough preparation process, enhances the activity of yeast, improves the structure and appearance of the product. Milk whey helps to save flour, increasing the yield of bread by 0.5–0.6%.

Useful properties of milk
A frequent occurrence, especially in the elderly, is a violation of cholesterol metabolism, resulting in the development of a disease such as atherosclerosis, which is characterized by the deposition on the inner walls of the arteries of cholesterol, its compounds and related lipids.

As a result, plaques form inside the arteries, which can ulcerate and form blood clots. Lime may also be deposited on these plaques.

Word "Cholesterol" comes from the Greek "cholesterol", which means "solid bile".

Milk is very useful for normalizing cholesterol metabolism. In addition, it has a beneficial effect on the functioning of the digestive system. The positive effect of milk is due to the content of a large amount of water in its composition and the presence of methionine, which is involved in the formation of hemoglobin.

Scientists have also found that milk stimulates the kidneys. Milk and dairy products are the best way to normalize the composition of the intestinal microflora, preventing putrefactive processes.

Eating milk and dairy products helps protect the body from reducing the sensitivity of cells to the hormone insulin. According to scientific studies, people who consume milk, butter, yogurt and cheese daily are less likely to have high cholesterol and high blood pressure associated with this condition. Dairy diet significantly reduces the risk of insulin resistance syndrome and obesity, which often lead to the development of cardiovascular disease and diabetes.

According to scientists, calcium, potassium and magnesium contained in dairy products reduce the likelihood of developing hypertension, as well as heart attack, stroke and diabetes.

Dairy products
Dairy products изготавливают из молока или сливок путем сквашивания с использованием различных заквасок. They consist of different cultures of lactic acid bacteria, which have different effects on the human body.

Sour milk is digested better than fresh milk. It is richer in vitamins, more biologically active and stronger in antibacterial action. Dairy products обладают целебными свойствами в большей степени, чем обычное молоко.

These products have been part of the human diet since ancient times. For their preparation, in addition to cow, sheep, goat, mare, donkey, camel, deer and buffalo milk are used. Fermentation was the main method of preservation and a necessary step in the preparation of cottage cheese and cheese.

In ancient Greece, a young man fell ill in a noble family. He was not helped by any drugs and medicinal herbs. Hippocrates ordered the patient to consume diluted donkey milk in the morning and evening for a week, and for the next weeks - cow's milk. The young man was soon on the mend.

In 1900, a population census was conducted in 18 European countries. As a result, it became known that the largest number of people over 100 years old live in poor Bulgaria with a population of 5 million people. There were registered 3732 people who crossed the 100-year mark, 10 people at the age of 120 years and 4 people at the age of 125 years. For comparison: in the richest European country, Switzerland, no more than 5 people over 100 years old were registered.

The explanation for the amazing longevity of the Bulgarians was given by the Russian scientist I. I. Mechnikov, the founder of immunology, who in 1903 published a book in Paris called "Etudes on the Nature of Man." According to his theory, food residues accumulate in the human large intestine, which do not have time to be digested in the small intestine. These are mainly animal and vegetable proteins. In the large intestine, they are not broken down, but decomposed by bacteria, resulting in the formation of toxic substances - ammonium, amides, phenols, thiols, indoles, etc. These toxins are absorbed through the intestinal wall into the lymph and blood and are carried throughout the body, causing damage to various tissues and organs. Self-poisoning of the body occurs, leading to its rapid aging. This theory is still relevant today.

In light of this statement, fermented milk products are of great importance. Lactic acid bacteria break down lactose, resulting in the formation of lactic acid. It is absorbed into the blood in the small intestine, but some of it also enters the large intestine, along with the remnants of lactose that has not had time to break down. Lactic acid fermentation in the large intestine inhibits the development of putrefactive microflora there and prevents the formation of toxins.

Mechnikov discovered a microbe in Bulgarian yogurt and named it "Bulgarian stick". Later, other lactobacilli were discovered, for example, acidophilus bacillus, which is most resistant to gastric acid and inhibits the development of not only putrefactive bacteria in the large intestine, but also some microbes.

Молочный жир очень тонко раздроблен в растворе сахара, солей и других substances. Fat particles are so small that there are several million of them in 1 drop of milk. Such fragmentation, or dispersion, of milk fat contributes to its good absorption and assimilation by the human body.

Thus, fermented milk products can rightfully be called the elixir of youth. Since the beginning of the XX century. all over the world, research on the healing properties of fermented milk products did not stop. The usefulness of fermented milk products has been scientifically proven. The results of studies have shown that lacto- and bifidobacteria significantly reduce the risk of cancer of the rectum and colon. Lactic acid bacteria have a therapeutic effect in gastroenteritis, infectious diarrhea, colitis, constipation and other intestinal diseases. They are very helpful in restoring the intestinal microflora after undergoing antibiotic treatment.

Dairy products делятся на 2 вида:

- products of lactic fermentation (yogurt, acidophilus milk, etc.);

- sour-milk drinks and products of mixed sour-milk and alcoholic fermentation (kefir, koumiss, ayran, acidophilus-yeast milk, etc.).

To prepare fermented milk products at home, milk is first pasteurized, then cooled and fermented with pure cultures. At dairies, as mentioned above, fermented milk products are prepared by thermostatic and reservoir methods.

The alcohol content in fermented milk products is low, but it is alcoholic fermentation that gives the drinks a specific stinging taste.

Pure bacterial cultures
These cultures include: lactic acid streptococcus, aroma-forming bacteria, acidophilus bacillus, Bulgarian bacillus, etc. The final product will depend on which starter the manufacturer prefers.

Lactic bacteria are shaped like sticks, some of the cells can take the form of balls. Bacteria reproduce by division, forming long chains. Lactic acid bacteria obtain energy for metabolism from their own cells as a result of lactic acid fermentation.

Scientists have studied curdled milk, which is formed from raw milk left at room temperature. This product is dominated by lactic acid bacteria, but it may also contain microbes that cause disease or give the product an unpleasant odor and taste. As a result, useful microorganisms were isolated and cultivated (grown) from fermented milk products. So pure cultures of lactic acid microorganisms appeared, which are currently used in dairy enterprises.

At the dairy, almost all microorganisms are destroyed by pasteurization in milk, after which pure cultures of microorganisms specific to each fermented milk product are introduced into it, and a product with a characteristic taste, aroma and dietary properties is obtained.

Soим образом, в приготовлении кисломолочных продуктов самую важную роль играет подбор культур молочнокислых бактерий и создание условий для их оптимального развития.

Up to 99.9% of microorganisms in milk are destroyed by modern methods of pasteurization at dairy enterprises.

Lactic acid bacteria are in the form of sticks or balls connected in pairs or in a chain. Spherical bacteria - lactic acid streptococci. Unlike sticks, they are able to multiply at lower temperatures (28–32 °C) and form a more tender and less acidic clot. The sticks multiply at a temperature of 40-45 ° C, forming a dense clot with a pronounced sour taste.

In many cities there are special laboratories that prepare pure cultures in the form of dry and liquid starter cultures. They are accompanied by instructions that contain the following information:

- for which lactic acid product is the culture intended;

- how much milk can be fermented with the contents of one test tube;

How to make liquid sourdough from dry sourdough.

With the help of this instruction, you can cook at home any fermented milk product based on milk alone or with the addition of sugar.

According to the type of fermentation, bacteria are divided into homofermentative and heterofermentative. Homofermentative bacteria in the process of fermentation convert carbohydrates into lactic acid (90%) and some other substances (10%). Heterofermentative bacteria during fermentation convert carbohydrates into lactic acid (50%), carbonic acid (25%) and acetic acid with ethyl alcohol (25%).

Lactic acid bacteria, getting into the stomach and intestines, become an integral part of the mucosal microflora. This is especially true for bifidobacteria. Some bacteria produce enzymes that break down proteins into simpler compounds, making food easier to digest. Others produce antibiotics, which gives fermented milk product therapeutic and prophylactic properties.

Bacterial cultures are thermophilic (heat-loving) and mesophilic