Freeze Drying

Freeze drying, also called lyophilization or cryodesiccation, is a low-temperature dehydration process that freezes a product and then reduces the surrounding pressure so its ice sublimates directly away, rather than removing water with heat as conventional dehydration does. Because so little heat is used, rehydrated freeze-dried food keeps close to its original shape, flavor and structure, which is why the method is used for high-value produce and for food meant for military rations, space missions and hiking supplies, with properly packaged products reaching shelf lives beyond twelve months. Ancient cultures freeze-dried food long before the modern process existed, including the Inca, who made chuno from potatoes, and the Japanese, who made koya-dofu from tofu; industrial freeze drying itself dates to the 1890s and became commercially important during World War II, when it was used to preserve blood plasma and penicillin.