Residual Water Content In Freeze-Dried Product: Importance, Location And Distribution

By Sophie Koenig, Biopharma Technology Limited

How Dry is Dry Enough?
Freeze drying is carried out to enable long term storage. Water affects many products both chemically and physically, so removing the moisture stabilises the product so that its immunologic potency, viability and integrity are not compromised. Dried products are not completely inert, and the moisture content within a freeze dried material has a direct effect on the glass transition of the material which in turn impacts on long term stability and storage conditions. Therefore the final moisture content of a product must be controlled within established tolerances.