Milk and dairy products are essential goods. Especially children and elderly people need them. There is an opinion that drinking milk is useless after treatment. Is it so? And if you drink raw milk? What do we know and have never thought about when buying a favorite product of most people?
Bacteria
Raw milk always contains a certain amount of bacteria. They are found even in compliance with sanitary rules. If you add imperfect milking conditions, milk is literally teeming with microorganisms. There are enough microbes on the surface of the udder and the hands of millers. Milking equipment, dishes and even air are saturated with different types of microbes. Can raw milk be eaten? What happens to dairy products after processing?
Fresh milk has a very diverse microflora. In it you can find lactic acid bacteria, E. coli, enterococci, yeast and other types of microorganisms. Among them are those that determine the various undesirable properties of milk. It can be bitter, bluish, reddish, viscous, have an unpleasant odor. When the microbiology of milk and dairy products is carried out, experts often find pathogens of various kinds of infectious diseases and food poisoning. These are dysentery, brucellosis, typhoid fever, tuberculosis, Staphylococcus aureus, Salmonella and other types of dangerous microorganisms.
What happens after milking?
When storing milk, the ratio between microorganisms undergoes some quantitative and qualitative changes. The nature of these processes depends on temperature, the duration of storage of the product and the initial microflora. At the same time, 60-80 degrees is the temperature of milk pasteurization, when some bacteria die, while others decrease their activity. So achieve the extension of the shelf life of the product.
Fresh milk contains bactericidal lactenins, due to which the development of bacteria is delayed in the first hours after milking. This period is called the bactericidal phase. The higher the temperature and the more bacteria, the sooner the product will begin to deteriorate.
What does the microbiology of milk and dairy products tell consumers
Freshly milked milk will have a temperature of about 35 degrees Celsius. When the temperature drops to thirty degrees, the bactericidal phase will last about 3 hours. Of course, if the product is not seeded with bacteria in excess. At twenty degrees, the shelf life of milk will be about 6 hours, at ten - about a day, and at five - one and a half days. If the temperature is zero, the bactericidal phase will last 48 hours. But you must always consider the number of bacteria in milk: the more there are, the more it will deteriorate.
The faster the milk is cooled, the longer the bactericidal phase will last. The higher the temperature, the faster the bacteria will multiply. The phase at which different bacteria begin to develop in the first hours of storage is called the mixed microflora phase.
What processes are taking place?
As the microbiology of milk and dairy products shows, by the end of this phase lactic acid bacteria are actively developing, causing an increase in acidity. As the acid accumulates, other bacteria develop. Others, for example, putrid, begin to die. A phase of lactic acid bacteria sets in, and the milk is fermented. If storage conditions are not met in the first hours, then the pasteurization temperature of milk of 60-80 degrees will provoke coagulation and the product will become unusable.
With an increase in acid concentration, even lactic acid bacteria are suppressed. The first to die are lactic streptococci. Subsequently, the growth of mold and yeast begins. These microorganisms contribute to the formation of alkaline protein breakdown products. Now acidity is reduced, and putrefactive bacteria can develop again.
Studying the microbiology of milk and dairy products, you will learn a lot of interesting things about these products. For example, at temperatures below 10–8 degrees Celsius, lactic acid bacteria practically do not multiply. But the cold-resistant bacteria are slowly gaining strength. For example, the decomposing proteins and fats of Pseudomonas. These bacteria contribute to the bitter taste of milk.
To preserve the freshness and vitamins necessary for humans in milk, it is cooled to 6-3 degrees at dairy farms. Only in chilled form it is delivered for processing. There, the milk is cleaned from mechanical impurities, pasteurization or sterilization. Cooled it is poured into containers and sent for sale.
As for dairy products, they play a big role in nutrition.
These are dietary products, and even medical ones. In comparison with whole milk, the fermented milk product has an increased storage stability. In addition, it is more easily absorbed by our body. But with all its value, it is a source of pathogenic bacteria, if you violate the preparation technology and storage conditions. It is very important in the process of fermentation to ensure the normal course of lactic acid fermentation.
When storing such a product, the development of yeast, acetic acid bacteria and mold may begin in it. Dangerous microorganisms enter the product from equipment, clothing and hands of workers, and, of course, from the air. The spoiled product has an unpleasant odor, taste defect and other signs of spoilage.