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单词 freeze drying
释义
freeze drying

Physics
  • A process used in dehydrating food, blood plasma, and other heat-sensitive substances. The product is deep-frozen and the ice trapped in it is removed by reducing the pressure and causing it to sublime. The water vapour is then removed, leaving an undamaged dry product.


Chemistry
  • A process used in dehydrating food, blood plasma, and other heat-sensitive substances. The product is deep-frozen and the ice trapped in it is removed by reducing the pressure and causing it to sublime. The water vapour is then removed, leaving an undamaged dry product.


Chemical Engineering
  • A process used to remove a solvent by sublimation from the frozen state. The process is used to preserve or extend the shelf-life of heat-sensitive mater-ials by removing the water (i.e the solvent) by rapid freezing and subsequent drying in a vacuum. Frozen water sublimes directly to the gas phase reducing the moisture content. The porous structure of the material is maintained by carefully applying heat. It is also known as lyophilization or cryodesiccation. A freeze dryer is a device used to remove the moisture of a body in which a vacuum is maintained. In freezing foods, the vacuum is maintained such that the water is frozen in the product and the moisture is removed by sublimation of the ice to water vapour. Freezer dryers are used for drying heat labile foods and pharmaceutical products that would otherwise be damaged if higher temperatures were to be used.


Biology
  • The removal of liquid from heat-sensitive materials. The material is frozen, placed under a high vacuum, and maintained at a low temperature (−40°C or below). The pressure generated by the vacuum causes the ice to turn from a solid to a gaseous form without passing through a liquid state. This allows the removal of water from the material without otherwise disturbing its composition. Freeze drying is used to preserve tissues (e.g. blood plasma) and foods and to concentrate solutions.


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