The rate of souring of milk depends on various factors, which are the reactor of the process of coagulation of milk protein. Milk protein (or casein) is completely dissolved in milk, and when sour it is released.
Milk curdling is a rather complex microbiological process. When milk is stored at room temperature, lactic acid bacteria multiply rapidly, which use the substances contained in milk (proteins, fats, sugar) for their own development. Compliance with storage conditions inhibits the reproduction of milk fungus.
The most common lactic acid bacteria are acidophilic, thermophilic, mesophilic bacteria, bifidobacteria. In the process of their vital activity, they not only feed on the constituent parts of milk, but also secrete lactic acid, which is the cause of sour milk. This is the natural process of protein secretion.
Artificial souring is facilitated by the use of various acids (for example, vinegar), which, when released into milk, leads to the release of milk protein. This process does not take place in a few days (as with natural souring), but in a few seconds.
There is also a belief that during a thunderstorm, milk turns sour quite quickly, of course, if it is not stored in the refrigerator. This is due to the fact that the effect of electromagnetic pulses of long frequency occurs. According to another version, sour milk during a thunderstorm occurs due to the interaction of protein with calcium, which leads to its curdling.
It is possible to prevent spoilage of milk by pasteurization and boiling, since during heat treatment the milk fungus dies. But it should be noted that sometimes during boiling, milk is quickly curdled. This is the reason that the milk fungus managed to prepare the required amount of acid.
As a rule, only natural milk sour, and not the one that is sold in stores, since the product goes through a technological cycle and undergoes various types of processing.
