Milk is a drink loved by both adults and children. It's good for your health and is a good thirst quencher. But milk is difficult to store - it can turn sour, change its structure and taste. Why is this happening and how to avoid it?
In order to understand the reasons for sour milk, you need to understand what this drink is. Milk contains many useful substances. Its important component is animal protein, and it also contains dissolved fats and sugars. All these components can serve as food for lactic acid bacteria. When bacteria begin to multiply, various chemical reactions take place in the milk, including protein folding. That is why milk turns sour, that is, it thickens, and also separates into two components - whey and a thicker curdled part. What provokes the multiplication of bacteria? First of all, it is the storage temperature. Room temperature is enough to provoke a reaction. Therefore, milk must be stored in the refrigerator or some other cool place if you want to keep it fresh, and the risk of sour milk can be reduced by special heat treatment. There are two types of such processing - pasteurization and sterilization. During pasteurization, milk is heated to 60-80 degrees Celsius and is in this temperature regime from thirty minutes to an hour. After this process, the shelf life of milk is increased by several days due to the fact that a significant part of lactic acid bacteria is killed. Another way to preserve milk is sterilization. In this case, the liquid is heated to boiling point. Such milk can be stored in sealed containers for several months. This is convenient, but there are some disadvantages - the beneficial properties of such milk are reduced. When preparing dairy products, people often ferment milk on purpose. In this case, the chemical process begins by adding special lactic acid bacteria, for example, bifidobacteria, to the liquid to obtain a product with special properties.
