Lyophilization is the process of removing water from a material after the product is frozen. Also known as freeze drying, lyophilization allows the ice to change from a solid directly to vapor without passing through the liquid phase. Mainly utilized by the pharmaceutical and food industries, lyophilization preserves perishable products by maintaining quality while increasing shelf life.
The low temperature process occurs in three phases, which if properly executed could reduce drying times by 30%.
No matter the method of freezing being used, cooling the material below its triple point ensures sublimation rather than melting occurs. This is the most critical phase in order to preserve the material’s physical form. To achieve lyophilization faster, the product can be frozen slowly to produce larger ice crystals. However, large ice crystals are not recommended for use with biological materials as they could break cell walls.
- Primary Drying (Sublimation)
During primary drying, pressure is lowered, and heat is added to the material in order for the ice to sublimate. This phase may last several days depending on the material, because if too much heat is added it could alter the structure of the material. In the end, about 95% of the water in the material is removed.
- Secondary Drying (Adsorption)
The final phase removes the ionically bound water molecules. First, the temperature is raised higher than it was during primary drying, and pressure is lowered to encourage adsorption. Once lyophilization is complete and the material is sealed, the final residual water content is between 1% to 4%.
To ensure the quality of the materials are maintained during lyophilization, data loggers are implemented to constantly monitor and track the temperature throughout the process. The MadgeTech LyoTemp data logger is specially designed to validate the lyophilization process. Capable of recording temperatures between -60 °C and 75 °C, the LyoTemp is equipped with a flexible probe for vial and/or surface temperature measurements and boasts an accuracy of ±0.5 °C.