Freeze-drying is a drying technique that utilizes the principle of sublimation. It involves rapidly freezing the substance to be dried at low temperatures, then, under a suitable vacuum environment, causing the frozen water molecules to sublimate directly into water vapor and escape. The product of freeze-drying is called lyophilized material, and the process is called freeze-drying. Before drying, the substance remains at a low temperature (frozen state), and ice crystals are uniformly distributed throughout the substance. The sublimation process avoids concentration due to dehydration, preventing foaming and oxidation caused by water vapor. The dried substance has a porous, sponge-like structure, its volume remains essentially unchanged, it is easily soluble in water and returns to its original state, and the process prevents physical, chemical, and biological denaturation of the dried substance.

Tags: