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How to Freeze Dry Vegetables
Publisher:   Source:   Date:2017-05-22   Clicks: 
How to Freeze Dry Vegetables

Freeze dried vegetables need to adopt vacuum freeze-drying technology to dehydrate fresh vegetables. The lyophilizing principle is to quickly freeze the water in vegetables to ice status, and the ice will be directly sublimated to vapor and removed. Thus the fresh vegetables are dried. According to the freeze drying principle, we know if freeze dry the vegetables, the machine must have the function of quick-freezing. Please pay attention here the word is “quick-freezing” rather than simply freezing. Because the temperature of quick-freezing is lower, it makes the moisture in fresh vegetables quickly freeze into small ice crystal, thus avoiding the formation of larger ice crystal to break the internal structure of vegetables. So that it will result in decreasing the quality of finished products. In the meantime, the vegetable freeze drying machine is also required to have the function of vacuumizing. The lower the pressure, the sublimation temperature of ice will be lower. The freeze drying machine for vegetables is also equipped with the function of heating. Because ice sublimation also needs to absorb heating, appropriate heating will speed up the sublimation.
 
Before starting the business of freeze dried vegetables, you need to select a set of reliable and efficient vegetable freeze dryer. The freeze drying equipment for vegetables is different from pharmaceutical freeze dryer. Forpharmaceutical industry, especially injection drugs, there are strict operating procedures and hygienicpractices. It is enough if the freeze drying equipment for vegetable can meet the hygienic requirements of food grade. So how to freeze dry vegetables? It can be divided into the following main steps.
  1. Prepare fresh vegetables, clean and then cut into strips.
  2. Load the cutting vegetables into the tray, insert the temperature probe, and be ready to pre-freeze.
  3. Quickly freeze the vegetables in the trays till the inside of vegetables is also completely frozen.
  4. Cool the vapor condenser, whose function is to collect the sublimated vapor.
  5. When the temperature of vapor condenser reaches -40℃, then begin to vacuumize.
  6. When the vacuum level is below 50pa, start to heat for the quick-frozen vegetables.
 
During this process, ice in fresh vegetables will be removed step by step, directly being sublimated from solid status into vapor. In the meantime the vapor is condensed by vapor condenser. So the vapor gets frosted soon and accumulated on the surface of the vapor condenser. Continuously, the moisture in vegetables is completely removed to vapor condenser, finally the vegetables are dried. Then the frost will be melted by cool water or hot water. Some companies use synchronous electric heating method to defrost. By this way, it will delay the progress of sucking water, and can’t achieve the purpose of saving time. In the meantime, it will increase the energy consumption, so it is not widely applied.
 
When the product temperature and setting temperature are same, meanwhile the vacuum level reaches the limit no-load vacuum level, it indicates that the material has been freeze dried. At this moment, you can shut down, release the vacuum, unload the material, and fast pack. So a batch of fresh vegetables is freeze dried, the nutrition of freeze-dried vegetables will not be lost. The only removed substance is water, and don’t take away any other content. So, the size and shape of freeze-dried vegetables will not be changed. Freeze dried vegetables like sponge with good rehydration. Freeze-dried vegetables can be provided to consumers at any time, after adding water, they’re very close to fresh vegetables. So that you don’t need to eat anti-season vegetables any more. Grinded into powder, it can be used as natural pigment or food additives. Adding to flour, it’s not only with rich nutrition and without losing, but also be made into food with different colors, especially children like it. During the production process, when packing, it does not need to add any artificial pigment, additives, preservatives. The freeze dried crisp vegetables can be preserved for more than 2 years after being simply packed. With the improvement of people's living standards, this natural, no added, rich nutrient crisp vegetables will be more and more popular among consumers. For the short seasonal and high nutritional vegetables, it’s a very ideal investment project!
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