What is freeze drying technology?
Freeze drying technology is a method of using dry air with a humidity of only about 10 – 30% and a lower temperature of 35 – 60°C than normal drying temperature for drying. In other words, freeze drying is carried out under atmospheric pressure.
It can be seen that, the temperature of the drying environment is quite low because it only ranges from 35 – 60°C, so the product quality seems to be less affected, so it brings high economic value.
Working principle of freeze drying technology:
– Heat pump dryer is the reverse cycle of cold storage. Cold storage uses cold heat to preserve food. Heat is discharged to the outside environment. Drying room-drying chamber using heat pump uses both types of heat, the outdoor unit creates the drying temperature, and the indoor unit is responsible for dehumidifying.
– Heat pump dryer works by compressing refrigerant to high pressure and high temperature, helping this outdoor unit to generate heat to dry the air passing through to 80 – 90°C.
– Next, the liquid at high pressure passes through the expansion device under the action of the refrigerant throttle valve to turn from high pressure and low temperature into low pressure and low temperature to enter the indoor unit to help but condenser. water in the air and separates out.
– At the refrigerant unit, the refrigerant receives hot heat from the air in the drying chamber to vaporize, during the vaporization process the refrigerant will collect heat from the air in the drying chamber and cool it to separate moisture. After vaporization, the refrigerant (gas) will return to the compressor to continue a new cycle.
– The humid air in the drying chamber will be removed through the condensate discharger.
– The whole process takes place in a continuous refrigeration dryer, forming a cycle, which provides a fast and stable freeze drying process. It is this principle that helps products lose only water, dry quickly without any impact on nutritional value, color or taste.
– Drying products with a cold dryer will help bring high hygiene and safety due to no contamination from the environment. Especially, cold drying technology helps to dry products quickly, usually 10-20 times faster than conventional heat drying methods.
Advantages and disadvantages of freeze drying technology:
– Keep the color and nutrition of raw materials (vitamins in agricultural products are easily decomposed at high temperature).
– No dust, no weather dependence (because the oven is completely sealed, does not affect the environment, humidity).
– Not contaminated with toxic fumes like drying with fuel, do not pollute the environment.
– Thorough drying of the product helps to preserve it for a longer time.
– Fast drying time.
– Larger investment costs than traditional methods.
– Need a strong, stable power source.
Compared with vacuum sublimation drying, cold drying still makes the product shrink, not brittle. However, freeze drying has much lower investment and operating costs and is therefore suitable for a wide range of products.
Which production field is freeze drying technology suitable for?
Freeze-drying technology is suitable for products that need to be dried at low temperatures to preserve product properties, especially vitamins that are easily decomposed at high temperatures. Specifically, fruit and vegetable products, medicinal herbs, traditional and traditional medicines… In the condition that requires initial investment and high energy costs, this technology is not currently too suitable for mass production of products. like cereals, although it is perfectly possible to dry cereals with a cold dryer. However, some agricultural products with thick skins that are not sliced or with very high sugar content also have difficulty drying by freeze drying.
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