Pasteurization refers to the process of heating food in order to kill harmful organisms in the food, such as bacteria, viruses, protozoa, molds and yeasts. This sterilization method was named after its inventor, French scientist Louis Pasteur, and the first pasteurization experiment was carried out by Pasteur and Claude Bernard on April 20, 1862. 

Unlike sterilization, pasteurization does not kill all microbes (pathogens) in food.Its goal is to achieve a logarithmic reduction in living organisms, reducing their numbers so that they are less likely to cause disease (assuming that sterilized products are refrigerated and consumed before spoilage). Commercial food sterilization is not common because it affects the taste and quality of the product. 

Through this sterilization, all bacteria (such as Escherichia coli, Listeria monocytogenes and Salmonella and Enterobacter) are not completely eliminated, they are still present in sterilized products, but at a very low concentration. Cold storage can prevent bacteria from growing further, or very slowly. There are also some bacteria in the food that will not cause harm to the human body, but they can produce acids that make the milk

sour. These microbes are commonly called "lactobacilli" because they consume lactose in milk and produce acids. 

Pasteurization is a compromise. If you boil the food, you can kill all the bacteria to make the food sterile, but you often find that it destroys the taste and nutritional value of the food. When you pasteurize a food (almost all liquid products), heat the food high enough to kill a certain amount of bacteria (not all) and disable a certain amount of enzymes. at the same time, you can minimize the effect on the taste of the food. The pasteurization condition of milk is 145 degrees Fahrenheit (62.8 ℃) for half an hour or 163 degrees Fahrenheit (72.8 ℃) for 15 seconds. 

There are three forms of pasteurization: intermittent pasteurization or tank pasteurization, high-temperature short-time pasteurization and ultra-high temperature pasteurization. 

Intermittent pasteurization or trough pasteurization is the early form of pasteurization adopted by zui, which heats the product to 145 degrees Fahrenheit for 30 minutes and kills most common bacteria. This method requires a large slot or b ucket, so it requires a lot of space. For this reason, only a small number of factories use this method of sterilization. 

The second method is pasteurization at high temperature for a short time. As its name suggests, it is a method of higher temperatures and shorter periods of time. This is a widely used processing method. For pasteurization of milk, the "heat preservation temperature" is 161F, which is a continuous processing process using "insulation pipes". The "thermal insulation pipe" is the pipeline transportation system after heating the milk products. The size of the pipe is fixed, ensuring that the time experienced by the product after passing through all the pipes is 15-20 seconds. When the product is sterilized, if the temperature is 161 degrees Fahrenheit or higher, it is called pasteurization. The product is then cooled and stored. 
The third method is ultra-high temperature pasteurization. This method is mainly used in coffee cheese and boxed fruit juices except in Europe. Milk is sterilized in this way. These products will be heated to temperatures above boiling point and instantly sterilized at 250 degrees Fahrenheit (under pressure).Products coming out in this way do not need to be refrigerated because they are sterile. Sometimes it is found that after such a high temperature, the product will have a cooked taste. This method has great defects, such as aseptic packaging after ultra-high temperature pasteurization of dairy products, which will cause a large loss of some important nutrients in milk, such as vitamins (vitamin products, vitamin information) and amino acids (amino acid products, amino acid information). At the same time, the chemical reaction formed by high temperature leads to milk discoloration and more precipitation.