There is no doubt about the facts on the benefits of living bacteria contained in yogurt. In addition, yogurt is easy to prepare at home.
In accordance with the technical regulations, ” yoghurt is a sour-milk product with an increased content of dry skimmed milk products produced using a mixture of starter microorganisms – thermophilic lactic-acid streptococci and Bulgarian lactobacillus”
The quantity of lactic acid microorganisms is also determined by the technical regulations and should be at least 1 • 10 7 CFU / g, which must be indicated on the package. The number of CFUs is the number of colony-forming units, that is, living lactic acid microorganisms (from each CFU in the laboratory studies the visible colony grows) 6, p. 49. In addition, one should pay attention to the storage temperature: “If the main thing for us is the presence of living microorganisms, then it is worth choosing the most” green “yogurt available. It should be called “yogurt”, there should not be anything in the composition, except milk and leaven (as a thickener by technical regulations is legalized milk powder), the packaging must necessarily indicate the amount of CFU at the end of the shelf life (if it exceeds 72 hours), and also recommendations for storage (4 ± 2 ? ?), and in the store such a product should stand exactly on cold shelves “6, p. 51.
In fact, this is a controlled process of coagulation of milk, which is caused to deteriorate in a certain way.
In order to lay the foundation for the necessary final consistency of yogurt, in industrial conditions milk is mixed in an apparatus similar to a washing machine.
Later, when the milk starts to curdle, and the proteins – stick together, the fat more evenly distributed throughout the product.
Then the milk is heated to kill any remaining harmful bacteria in it, and also to start the process of unfolding the protein molecules, which in this case form a lattice – the basis of the yoghurt structure.
In industry, as a rule, the temperature is brought to 85 ° C and the milk is left for 30 minutes, or 90-95 ° C for 5 minutes.
After cooling the heated milk to about 37 ° C, the most important, in the opinion of many, process in the production of yogurt is fermentation.
This temperature is favorable for the life of the two most commonly used bacteria in the preparation of yoghurt
During the process of reproduction, bacteria convert lactose (sugar contained in milk) into lactic acid, with an increase in the content of which the acid-base balance of milk begins to decrease.
Milk proteins respond to this change. Until now, they were in a “stuck together” state – either in the form of a shell of droplets of fat, or in separate small clots.
This state of proteins was stable due to the presence of a salt in milk, known as calcium phosphate.
Now, with a decrease in the acid-base balance, this salt dissolves, and the clots of proteins begin to disintegrate.
Individual proteins form a lattice, the cells of which capture droplets of water and fat. So the milk turns into yogurt.
The fermentation process is stopped by cooling the yogurt, resulting in a gelatinous mass.
In the production of filtered yogurt like the Greek, there is another stage in which the “jelly” is stratified by stirring, and then water, sugar and proteins are separated from the final product in the form of whey.
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