jäädytysmenetelmä

Jäädytysmenetelmä, known in English as freeze-drying or lyophilization, is a dehydration process typically used to preserve perishable materials or make them more convenient for transport. The process involves freezing the material and then reducing the surrounding pressure to allow the frozen water in the material to sublimate directly from the solid phase to the gas phase. This differs from air drying, which uses heat, as freeze-drying does not cause heat damage to the product.

The freeze-drying process involves three main stages: freezing, primary drying, and secondary drying. In the freezing stage, the material is cooled below its triple point to freeze its water content. This is a critical step as the ice crystal structure formed can affect the final product. The primary drying stage involves applying a vacuum and heat to the frozen material, causing the ice to sublimate. Most of the water is removed during this stage. The secondary drying stage removes any remaining unbound water molecules, further reducing the moisture content and increasing the product's shelf life.

Freeze-drying is commonly used in various industries. In the pharmaceutical industry, it is used to preserve vaccines, antibiotics, and other sensitive biologicals. The food industry utilizes freeze-drying to produce instant coffee, dried fruits, and long-lasting emergency food supplies. It is also employed in the preservation of biological samples for research and in the restoration of water-damaged books and documents. The main advantage of freeze-drying is that it preserves the material's structure, chemical composition, and biological activity, resulting in a high-quality end product that can often be reconstituted by simply adding water.