Freeze-drying refers to "freeze-drying. Freeze-drying pre-freeze a substance containing a large amount of water, crystallize the free water in the substance, freeze it into a solid, and then sublime the ice crystal in the substance under high vacuum conditions. After the ice crystals sublime, part of the adsorbed water in the substance is removed, and finally, a dry product with a residual water content of about 1% to 4% is obtained. The food produced by this method is called freeze-dried food.
Freeze drying has the following advantages:
Freeze-drying is carried out at low temperatures without denaturation or loss of biological activity of proteins and microorganisms.
When drying at low temperature, some volatile components in the material are lost very little.
During the freeze-drying process, the growth of microorganisms and the action of enzymes cannot proceed so that the original properties can be maintained.
After adding water, it dissolves rapidly and completely and restores its original properties almost immediately.
Some oxidizable substances are protected since drying takes place under a vacuum with very little oxygen.