The vacuum freeze dryer is suitable for drying high-grade raw materials, biological, vegetables, food, fruits, chemicals, pharmaceutical intermediates and other materials. Vacuum freeze drying is a new type of box structure that combines the refrigeration system, vacuum system, heat transfer oil heating system, and moisture removal system of the vacuum freeze dryer. It uses the space for storing materials in the box to dry.
The production process of vacuum freeze-dried food is divided into material selection, cleaning, cutting, blanching, sterilization and other procedures. It needs to remove insects, eggs, and sediment attached to the roots, stems and leaves, remove metal debris with a magnetic field, remove foreign matter such as hair and scales with static electricity, and avoid overheating. Only with good pre-treatment can it be possible to produce high-quality freeze-dried food.
Quick-freeze the pre-treated materials, the faster the freezing, the smaller the crystals in the materials, and the less damage to the structure and organization of the materials. The freezing time is short, and the protein will not change qualitatively under the action of coagulation and concentration.
The quick-frozen food must be vacuum-sublimated and dried quickly, and the vacuum degree is required to reach the sublimation pressure quickly, and the sublimation heat energy is supplied in time to maintain the sublimation temperature. Radiation heating is generally used.
Freeze-dried food is porous, and the surface of the tissue is 100 to 150 times larger than the original, so the chance of contact with oxygen increases. When returning to normal pressure from low temperature and low pressure, it should be carried out in a nitrogen environment. Crushing and packaging should be carried out at a relative humidity of 30-40% and a temperature below 25℃. In order to keep the moisture content of dried food below 5%, a desiccant should be placed in the package to absorb a small amount of moisture. Packaging materials should be selected with poor air permeability, high strength and deep color.
Freeze-drying technology can process various vegetables, fruits, fish, instant noodles, condiments, coffee, tea, etc.
