Vacuum freeze-drying, also known as freeze-drying, refers to the process of removing moisture or other solvents from frozen biological products through sublimation. Sublimation refers to the process of freezing water in a product into ice, allowing it to change directly from a solid state to a gaseous state without going through a liquid state. The product obtained from freeze-drying is called lyophilizer, and this process is called freeze-drying. Traditional drying can cause material shrinkage and damage cells. Utilizing the three-phase principle of water during freeze-drying, as shown in the figure

At this point, the structure of the sample will not be destroyed because the solid components are supported by the strong ice at their positions. When ice sublimates, it leaves pores in the remaining dry material. This preserves the integrity of the biological and chemical structure and activity of the product.