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The basic principle of freeze-drying is based on the three state changes of water. Water can exist in solid, liquid, and gas states, which can both be converted and coexist with each other. When water is at the triple point (temperature of 0.01 ℃, water vapor pressure of 610.5Pa), water, ice, and water vapor can coexist and be in equilibrium with each other. Under high vacuum conditions, utilizing the principle of sublimation, the moisture in pre frozen materials is directly removed as water vapor through ice sublimation without melting, thus achieving the purpose of freeze-drying. 

The freeze-dried products produced by Shanghai Yetuo freeze-drying machine are sponge like, have no drying shrinkage, have excellent rehydration properties, and contain very little moisture. After packaging, they can be stored and transported at room temperature for a long time. Due to its unparalleled advantages over other drying methods, vacuum freeze-drying has been increasingly favored by people since its inception, and its applications in medicine, biological products, and food have become increasingly widespread. Serum, bacterial strains, traditional Chinese and Western medicine and other biological products are mostly bioactive substances, and vacuum freeze-drying technology also provides a good solution for preserving biological activity