The principles of freeze drying are simple. This provides a necessary condition for low temperature drying. After freezing, the product is placed under vacuum. This enables the frozen solvent in the product to vaporize without passing through the liquid phase, a process known as sublimation.
Heat is applied to the frozen product to accelerate sublimation.
This completes the seperation process. While simple in principle, freeze drying can be complix in practice due to the specific processing requirements for different products. Rate of freezing. Residual moisture content. Storage temperature and atmosphere after drying.