Lyophilization and freeze drying are synonymous. The sterile lyophilization technique is a water removal process typically used to preserve perishable materials, to extend shelf life or to make materials more convenient for transport. Lyophilization works by freezing materials, then reducing the pressure and adding heat to allow the frozen water in the material to sublimate. Freeze drying or the sterile lyophilization technique retains the physical structure of materials and thereby preserves them for transport.
Freeze drying or lyophilization contract services may be used so that products remain stable and are easier to store at room temperature. Biological materials in particular should be dried to stabilize them for storage, preservation and shipping. Lyophilization contract services significantly reduce damage to biological samples. It consists of three separate, unique, and interdependent processes; freezing, primary drying (sublimation), and secondary drying (desorption).
- Freezing Phase
During this preliminary stage, a sample is frozen, which means the water in the product is converted to ice, thereby the phase has changed from liquid to solid.
- Primary Drying (Sublimation) Phase
Primary drying is the most time-consuming and energy-intensive step in freeze-drying bulk products or the sterile lyophilization technique. During the primary drying phase, pressure is lowered and enough heat is supplied to the material for the water to sublimate. Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state.
- Secondary Drying (Desorption) Phase
Finally, any residual water present, which is strongly bound to the molecules of the sample, is converted to vapour and removed from the sample via a process called desorption.
Controlled freeze-drying keeps the product temperature low enough during the process to avoid changes in the dried product appearance and characteristics. It is an excellent method for preserving a wide variety of heat-sensitive materials such as proteins, microbes, pharmaceuticals, tissues and plasma.
Moreover, freeze drying capabilities may be used to prepare dosage forms that are to be reconstituted for injection. Lyophilization contract services are also used in the biotechnology and biomedical industries to preserve vaccines, blood samples, purified proteins, and other biological material.