The Technical Characteristics Of Fruit And Vegetable Freeze-Drying And The Principle Of Food Freeze-Drying

Food freeze-drying technology is also called food vacuum freeze-drying technology. The main advantage is that it can maintain the color, aroma, taste, and shape of fresh food, maximize the preservation of vitamins, protein and other nutrients in the food, and has good rehydration. It can be stored for a long time at room temperature, so it is widely used in convenience foods and prepared foods. Freeze-drying is a technology with high technological content and wide application in the field of drying technology. Because its products have green, convenient and health-care functions, they are well received by everyone.

The principle of food freeze-drying: According to the phase equilibrium theory in thermodynamics, the temperature of the triple point of water (the coexistence of vapor, liquid and solid) is 0.0098℃, and the pressure of the triple point is 609.3pa (4·57mm/mg) in water. During the phase change process, when the pressure is lower than the triple point pressure, solid ice can be directly converted into gaseous water vapor, that is, ice crystal sublimation.

The principle of food freeze-drying is to pre-freeze fresh foods containing a lot of water to crystallize free water in the fresh foods and freeze them into solids, then sublime the ice crystals in the food under high vacuum conditions, and then remove the food after the ice crystals sublimate. The middle part absorbs water, and finally a dry product with a residual water content of about 1-4% is obtained, that is, freeze-dried food. Equipment for processing freeze-dried food is also called food freeze dryer

Features Of Food Freeze-Drying Technology

1. In the process of food drying, the temperature must be controlled within the range of -40°C to +55°C. At the same time, the surrounding environment must be in a high vacuum state during the processing, so this processing method In food processing with high heat sensitivity and very prone to oxidation problems, it not only retains the food's own taste, but also protects the nutrient content of the food.

2. The dried product will not lose the original skeleton structure, and the original shape of the material can be maintained to the greatest extent.

3. The food processed by freeze-drying technology has a porous structure, so it has good rehydration, and it dissolves in water very quickly. In this case, the freshness of the food is also very good. .

4. In the process of sublimation, water-soluble substances can be smoothly precipitated, which also effectively prevents other drying methods from losing nutrients and inorganic salts due to the transfer of water inside the material to the surface of the material, which can be maximized Keep the nutrient content of the substance.

5. Freeze-dried food is packaged in vacuum or nitrogen flushing during the production process, and it can also be stored under dark conditions. Therefore, the shelf life of such substances can be as long as five years. Compared with quick-frozen food, it is not Need to transport and store, this processing method can be very effective to improve the quality of the product.