What happens during lyophilization/freeze-drying?
Freeze-drying is a two-stage high-tech procedure for the gentle drying of valuable products. It uses the physical rule that ice in a vacuum is converted directly to steam without the water thawing out. This process of direct conversion from solid ice to steam is called sublimation. In Phase I of freeze-drying the product to be dried, e.g. a homogeneous collagen or algae emulsion, is shock-frosted at extreme minus temperatures. In Phase II the product remains in a vacuum chamber for many hours or days. When a little heat is added, the ice transforms to steam and appears on the deep-frozen condensers in the form of ice. The result is a highly porous matrix. The three-dimensional structure of the product is maintained and the material does not shrivel up. The natural, biological and physical properties of the raw material are fully maintained. The cell systems which have been drained of water form a large inner surface which can be rapidly hydrated. The result is very high absorbency.
