Introduction to Freeze Drying

1: What is Freeze Drying?

As the name implies, freeze drying describes a process whereby something is frozen and then dried. Freeze drying is also known as lyophilization (or lyophilisation) which means "solvent-loving". This name illustrates a key aspect of the process in that the products that are to be dried must be easily soluble.

As a stepwise process, freeze-drying typically involves:
- Cooling of the initial formulation (which may be a solution, suspension, emulsion, slurry or a more complex mixture or structure)
- Freezing the solvent (usually water) into a solid
- Sublimation of the solid solvent (usually ice) under vacuum - "Primary Drying"
- Desorption of bound solvent remaining in the dried product - "Secondary Drying"
Afterwards, the product is often sealed in its container ("stoppered"). This can either under vacuum or ‘backfilled’ with a non-reactive gas such as nitrogen or argon

Freeze-drying is a unit operation that is widely used in the production of a wide range of products, including diagnostics, vaccines, pharmaceuticals, biotech products, foods and beverages.

Next: Freeze Dried Product

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