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Principle of freeze drying technology
- Jul 18, 2017 -

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Drying is one of the ways to keep the material from decaying. There are many drying methods, such as drying, boiling drying, drying, spray drying and vacuum drying, etc.. But these drying methods are carried out at temperatures above 0 or higher. Dried products, is generally smaller in size, hard texture, the oxidation of some substances, some volatile components in most of the loss, some heat sensitive substances, such as protein, vitamin degeneration. Microbes lose their biological activity and dry matter does not dissolve easily in water. Therefore, there is a great difference in the characters between the dried products and those before drying. The freeze drying method is different from the above drying method, drying the basic product at a temperature below 0 DEG C, that is, in the frozen state until later, in order to further reduce the residual moisture content of dried product, that product to a temperature above 0 DEG C, but generally not more than 40 DEG C.

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Freeze drying is the inclusion of a large number of water substances, pre cooling, frozen into solid, and then in the vacuum under the conditions of water vapor directly sublimation. The material itself remains in the ice shelf at the time of freezing, so it is dry and remains porous and porous. During sublimation, ice or other solvents are frozen in the product to absorb heat. The temperature of the product is reduced and the sublimation speed is reduced. In order to increase the sublimation speed and shorten the drying time, proper heating of the product must be carried out. The whole drying is carried out at a lower temperature.