Views:1 Author:Site Editor Publish Time: 2020-10-20 Origin:Site
The principle of pasteurization is that within a certain temperature range, the lower the temperature, the slower the bacteria multiply; the higher the temperature, the faster the multiplication. But if the temperature is too high, the bacteria will die. Different bacteria have different optimum growth temperature and heat and cold tolerance. Pasteurization is actually the use of pathogens that are not very heat-resistant, treatment with appropriate temperature and holding time to kill them all. However, after pasteurization, a small part of harmless or beneficial, more heat-resistant bacteria or bacterial spores remained.
It is a kind of sterilization method for milk, which can kill pathogenic bacteria harmful to health and make the milk quality change as little as possible. That is, based on the difference principle between the heat lethal curve of tuberculosis, which is extremely resistant to high temperature, and the separation heat damage curve of cream, which is most easily affected by heat in milk, a kind of heat treatment at low temperature for a long time or high temperature for a short time. method. Among them, the method of heating for 30 minutes below 60°C has long been widely adopted in the world as a standard for low-temperature sterilization. The use of high temperature treatment has some influence on the milk quality, but it 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.
Usually, milk in bags sold on the market is produced by pasteurization. The fresh milk is collected by the factory, processed at low temperature, and then sterilized by pasteurization. Milk in bags 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 this.
It should be pointed out that drinking fresh milk (referring to milk that has just been squeezed out) is not safe because it may contain harmful bacteria to our bodies. Another point is that pasteurization is not a panacea. The pasteurized milk must still be stored at a lower temperature (generally <4°C), otherwise there is still the possibility of deterioration. Therefore, many methods of selling milk in bags on the market are very irregular.
Pasteurized milk is the most consumed milk variety in the world. The consumption of pasteurized milk in the United Kingdom, Australia, the United States, Canada and other countries accounts for more than 80% of liquid milk. The varieties are fully skimmed, semi-skimmed or full-fat. In the US market, almost all pasteurized milk is actually in large packages (1 liter, 2 liters, 1 gallon), and citizens 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 about 4°C, the reproduction of bacteria is very slow, and the nutrition and flavor of the milk can remain unchanged within a few days
Pasteurizers on the market are mainly used for commercial purposes. At the same time, pasteurization is also a general sterilization standard in the world. It is used in many large enterprises. The pure milk and other flavors of yogurt on the market are pasteurized. With the development of green and healthy food at any time, pasteurizers are used in many small dairy farms. Small dairy farms use 100 liters or 200 liters, mainly to make fresh pure milk and distribute it to the market. . The pasteurizer is equipped with a cold water circulation system. There are two common cooling methods. One is: compressor refrigeration, which is fast and effective, and the other is cold water circulation refrigeration, which is mainly used The physical cooling method will be much lower in cost.