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The lyophilization process involves three main sub-steps:
1. Freezing – Ice formation
2. Primary Drying – Sublimation
3. Secondary Drying – Desorption
One of the major advantages of using Lyophilization is that it consumes less heat for drying the product. Also, the harvested powder has enhanced integrity and stability. However, the major downfall of this process is increased cycle time.
Pre-Treatment Options
1. Preserving Appearance of the Product
Once the formulated product (e.g., cosmetics) enters into the commercial market, the physical properties become extremely important. For lower product concentrations, lyophilization may cause even a slight settling of the product in vials or bottles. For such products, third-party agents (also called bulking agents) are added to preserve the overall product appearance.
2. Stabilization of Reactive Products
In particular, biosimilar products are prone to witness irreversible changes in their molecular structure or degradation during lyophilization.This happens because lyophilization processes are carried out at much lower temperatures.
To save and stabilize the product from such serious issues, stabilizers (also called lyo-protectants) are introduced during lyophilization.
Moisture is one of the crucial factors contributing to degradation. Hence, along with such stabilizers, framing the moisture requirements is equally important.
3. Reduced Application of High Vapor Pressure Solvents
High vapor pressure solvents have very low freezing points. During the freeze-drying step, these solvents will come off at first rapidly. Also, for an excessive quantity of the solvent, a product may melt at high pressures in the chamber.
To remove such excessive solvents, pre-treatment involves the application of equipment like rota-vapors, centrifuges, etc. When the low temperature of the product is the priority we can use solvent traps such as liquid nitrogen traps in a vacuum line to remove excessive amounts of solvents.
