Vacuum freeze dryer and vacuum freeze dried food
Fast frozen fresh food, then dewatering in a vacuum container. Then, you can get freeze-dried food. Under vacuum conditions, Solid water (ice) can become gas directly, in this way, the material is dehydrated and dried.
Foods made by freeze-drying process are not only can keep full of color, aroma, taste, and shape, but also preserve vitamins, proteins and other nutrients in the food. Before serving, simple process can make them return to fresh food within a few minutes.
Freeze-dried food no needs to be stored in a cold temperature. After being sealed and packaged, it can be stored, transported and sold at room temperature for a long time. What’s more, it will not deteriorate within three to five years. Because freeze-dried foods have a moisture content of 5%, they are of good quality and light weight, which can greatly reduce their operating expenses.
For example, after the tomato sauce is processed by freeze-drying process, 1000 grams of fresh tomato sauce can be processed into 320 grams of freeze-dried tomato sauce powder, and it will be restored to tomato sauce when water is added. Loved by people. Today, freeze-dried tomato ketchup has become a replacement for normal tomato ketchup.
In the production of vacuum freeze-dried foods, there are generally processes such as material selection, cleaning, cutting, blanching, and sterilization. It is necessary to remove the insects, eggs and sediments attached to the roots, stems and leaves, use magnetic fields to remove metal debris, use static electricity to remove foreign matter such as hair, scales, etc. to avoid overheating. Regardless of cooking or dipping, it must be done according to process requirements. Good pre-treatment is necessary to produce high-quality freeze-dried food. The quicker the raw foodstuff is frozen, the smaller the crystals in the item, and the less damage to the structure and structure of the item. Since the freezing time is short, and the protein will not undergo qualitative change under the effect of coagulation and concentration.
Quick-frozen foods must be quickly sublimated and dried in vacuum. It is required that the degree of vacuum reaches the sublimation pressure quickly, and the sublimation heat energy is provided in time to maintain the sublimation temperature unchanged. Usually, radiant heating is 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 is increased. When returning to normal pressure from low temperature and low pressure, it should be performed in a nitrogen environment. Crushing and packaging should be performed at a relative humidity of 30 to 40% and a temperature below 25 ° C. In order to keep the dry food below 5% moisture, a desiccant should be placed in the package to absorb a small amount of moisture. Packaging materials should be selected for poor air permeability, high strength, and dark colors.