külmkuvatud

Külmkuvatud is an Estonian term that translates to freeze-dried in English. It refers to a process of dehydration that 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 method is often used for preserving perishable materials, such as food, pharmaceuticals, and biological specimens.

The freeze-drying process typically involves three main stages. First, the material is frozen, usually to a temperature below -20 degrees Celsius. This halts biological activity and prevents degradation. Second, the frozen material is placed in a vacuum chamber, and the temperature is gradually raised while maintaining a low pressure. In this stage, the ice crystals within the material sublimate, turning directly into water vapor, which is then removed. Finally, a secondary drying phase may be employed to remove any remaining unbound water molecules, further stabilizing the product.

Freeze-drying is advantageous because it preserves the physical structure and chemical properties of the original material to a greater extent than other drying methods. It results in a lightweight, shelf-stable product that can be easily rehydrated by adding water. This technique is widely used in the food industry for products like instant coffee, fruits, and vegetables, as well as in the pharmaceutical industry for producing stable vaccines and antibiotics. The resulting product is often referred to as "külmkuivatatud" in Estonian contexts.