In addition to the bacteria inherent in flour, there are also bacteria introduced by other contamination during processing. Due to the existence of bacteria, it will greatly affect the quality of food, leading to early spoilage and shortening the shelf life. Therefore, the sterilization process is an indispensable link in flour production.

　　(1) Microwave sterilization. Microwave refers to electromagnetic waves with a wavelength of 1mm to 1m and a frequency of 300MHz to 300GHz. Microwave sterilization has the characteristics of short sterilization time, fast heating rate, low energy consumption, uniform sterilization, and less damage and loss of food nutrients and flavor substances. The microwave sterilization equipment commonly used in its principle mainly includes box-type intermittent microwave sterilization device, microwave sterilization device, pressure-type microwave sterilization device, and pressure-conveyed microwave sterilization device for hot water.

　　There are still unstable factors and defects in microwave sterilization, such as uneven heating, microwave radiation will also cause certain damage to the human body, and it is also easy to cause damage to the packaging bag.

　　(2) Ultra-high pressure sterilization. After high pressure acts on the material, it will cause various changes in the morphological structure, biochemical reaction, genetic mechanism and cell wall membrane of the microorganism, thereby affecting the original physiological activity of the microorganism, destroying the original function or causing irreversible changes.

　　Ultra-high pressure sterilization can better maintain the original nutrients of the material, and the processed food has a suitable taste, bright color, and a long shelf life, and the energy consumption of the entire food processing process is low. However, the pressure of ultra-high pressure is very high during the sterilization process, and the pressure-sensitive components in the food are damaged to a certain extent. Because it is a common equipment, its equipment cost is lower than other sterilization equipment.

　　(3) Superheated steam sterilization (also known as dry heat sterilization). High-temperature superheated steam is used for sterilization, that is, the superheated steam with a temperature of 130~160℃ is used to spray the items to be sterilized, and the sterilization operation can be completed in a few seconds.