Freeze-dried - Tokukanso

This refers to vacuum drying a substance in a frozen state, in which any water contained in the substance vaporizes (sublimes) directly without passing through the liquid phase and is carried away into the exhaust system. It is usually performed in a vacuum of around 133 Pa or less, at a low temperature below 0°C. Materials that are heat-sensitive, contain a relatively large amount of water, and would deteriorate if left in their original state, such as medicines and food, can be dried using this method, and the resulting product can be stored for long periods of time. When freeze-dried in a vacuum, aromatic components and pigments remain attached to the tissue and are not lost along with the water. Furthermore, if an appropriate amount of water is added, the material will be restored to a shape and state close to its pre-drying state. It is particularly used to dry substances that are killed or deteriorated by heat, such as antibiotics, plasma, serum, and food.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

物質を凍結した状態で真空乾燥することをいい，物質中に含まれた水分は，液相を通らず直接気化(昇華)し，排気系に運び去られる．通常，133 Pa 程度以下の真空中で，0 ℃ 以下の低温で行う．薬品や食品など熱に敏感で，水分を比較的多く含み，そのままの状態では変質したりする材料はこの方法で乾燥され，得られたものは長期保存が可能である．凍結真空乾燥すると芳香成分や色素は組織についたままで，水分とともに失われることなく残る．また，これに適当に水分を加えると乾燥前の状態に近い形と状態で復元される．とくに抗生物質，血漿，血清，および食品など，熱によって死滅，あるいは変質するような物質の乾燥に用いられている．

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