As a sterilization method for milk, it can not only kill pathogenic bacteria harmful to health but also make milk quality change as little as possible. That is, according to the principle of difference between the thermal lethal curve of tuberculosis, which is highly resistant to high temperature, and the thermal destruction curve of cream separation, which is most easily affected by heat in milk, it is a kind of heat treatment at low temperature for a long time or at high temperature for a short time. method. Among them, heating below 60°C for 30 minutes, as a standard for low-temperature sterilization, has been widely used in the world. Using high temperature treatment, although it has some influence on milk quality, can enhance the sterilization effect. This method is called high temperature sterilization (sterilization), that is, heating above 95°C for 20 minutes. In addition to milk, pasteurization can also be applied to fermented products, food sterilization after vacuum packaging, etc.
Usually, the bagged milk sold in the market is produced by pasteurization. The fresh milk collected in the factory is treated at low temperature first, and then sterilized by pasteurization. Bags of milk produced in this way can usually be stored for a longer period of time. Of course, the specific treatment process and technology are much more complicated, but the general principle is like this.
It should be pointed out that it is not safe to drink fresh milk (referring to freshly squeezed milk), because it may contain bacteria that are harmful to our body. Another point is that pasteurization is not a panacea. Pasteurized milk should still be stored at a lower temperature (generally <4°C), otherwise there is still the possibility of spoilage. Therefore, many methods of selling bagged milk on the market are very irregular.
Pasteurized milk is the most consumed milk variety in the world. The consumption of pasteurized milk in the UK, Australia, the United States, Canada and other countries accounts for more than 80% of liquid milk. The varieties include full-skimmed, semi-skimmed or full-fat. In the U.S. market, almost all milk is pasteurized, and it comes in large packages (1 liter, 2 liters, 1 gallon). People can buy enough fresh milk for a week when they go to the supermarket. Sterilized pure milk is rarely sold in the market, and some small towns cannot buy it at all.
Pasteurized pure fresh milk better preserves the nutrition and natural flavor of milk, and is the best among all milk varieties. In fact, as long as the pasteurized milk is stored at a temperature of around 4°C, the bacteria will multiply very slowly, and the nutrition and flavor of the milk will remain unchanged within a few days.