1, chemical preservation: the use of chemicals, that is, preservatives to prevent and delay the deterioration of food.

2. Cryopreservation: Low temperature can weaken the general chemical reactions in food, reduce the activity of enzymes and inhibit the reproduction of microorganisms.

3. High-temperature preservation: After high-temperature treatment, most microorganisms are killed and enzymes are destroyed, so other preservation methods such as sealing, vacuum and cooling must be adopted to preserve food for a long time.

4. Drying and fresh-keeping: reduce the moisture content of food below a certain level, and inhibit the growth of microorganisms that can cause food spoilage and food poisoning.

5. Improve osmotic pressure to keep fresh: The practical application is mainly salt pickling and sugar pickling.

6. Irradiation preservation: refers to the treatment of food or food raw materials by artificially controlled radiant energy in order to achieve the purpose of sterilization, disinfestation and inhibition of germination.