Food Freeze Dry Machine—Freeze-Drying Process II


(2) Sublimation drying of Freeze Dry Machine It is the […]

(2) Sublimation drying of Freeze Dry Machine

It is the core process in the production of freeze-dried food to control the process conditions:

②Drying temperature In freeze-drying, in order to shorten the drying time, it is necessary to efficiently supply the heat required for sublimation of ice crystals, and thus various practical heating methods have been designed. The drying temperature must be controlled within a range that does not cause the ice crystals to melt in the material to be dried, and the dried portion does not cause heat denaturation due to overheating. Therefore, in the single heating mode, the temperature of the drying plate should be controlled at 70 to 80 ° C in the initial stage of sublimation drying, 60 ° C in the middle of drying, and 40 to 50 ° C in the late drying stage.

③Dry end point judgment Dry end point can be judged by the following indications: the material temperature and the heating plate temperature are basically consistent and maintained for a period of time; the pump set (or cold trap) vacuum gauge and the drying chamber vacuum gauge tend to be consistent and maintain a section Time; the drying chamber vacuum gauge cold trap temperature basically returns to the indicator when the equipment is empty and keeps for a period of time; for the freeze dryer with large butterfly valve, the large butterfly valve can be closed, and the vacuum machine basically does not drop or drop very little. The above four judgments can be used alone or in combination or in combination.

(3)Post processing of Freeze Dry Machine

Post-processing includes unloading, semi-finished product sorting, packaging and other processes.

After freeze-drying the knot speed, inject nitrogen or dry air into the drying chamber to break the vacuum, and then immediately remove the material in a closed environment with a relative humidity of 50% or less, a temperature of 22 to 25 ° C, and less dust, and in the same environment. The selection and packaging of semi-finished products. Because the lyophilized material has a large surface area and is very hygroscopic, it is necessary to complete the operations in a relatively dry environment.

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