Vacuum freeze-drying is a method of freezing the aqueous material, placing it under a vacuum and supplying a certain amount of heat, so that the water in the material is sublimated directly and drained. Vacuum freeze-drying technology originated in 1811, was used for dehydration of biological materials. This technology in the food processing applications, began during World War II, food vacuum freeze-drying industry, although the development history of only 50 years, but the development of fast, more and more applications, the product quality, the frozen Dry food is better than hot air drying, spray drying, vacuum drying and other traditional dehydrated food. In terms of transportation and storage costs, lyophilized foods are superior to frozen foods and canned food. As the freeze-dried food is easy to rehydrate, and the maximum retention of fresh food color, smell and taste, so many freeze-dried food is high quality instant food convenience food. As the freeze-dried food to maximize the retention of the nutritional content of food raw materials and physiological components, therefore, many functional food or its base using freeze-dried food, freeze-dried food high value-added can make up for its shortcomings of high production costs, This is especially true for expensive food ingredients.
With the continuous improvement of people's living standards, people's food requirements also followed a qualitative change, modern food consumption in addition to color, smell, taste and taste to meet, but also the pursuit of "natural, nutrition, safety, health care , Convenient "new yet Freeze-dried food is a good fit of the 'green food', 'convenience food' development trend. Freeze-drying method produced by the appearance of crystal products, taste good, nutritious, not perishable. Food corruption is mainly caused by micro-organisms, so as long as the advance to prevent the growth and reproduction of microorganisms, will be able to better maintain the quality of food. In the process of growth and reproduction of microorganisms in addition to the need for certain nutrients, but also must have enough water, microbial use of free water, combined with water can not be used. So as long as the food as much as possible to reduce the free water, microbes can not develop breeding, will be able to avoid the microbial effects arising from some adverse changes in the vacuum state, the use of sublimation principle, so that pre-frozen food moisture Ice melts directly to
Ice sublimation is the removal of water vapor, so that the food is dry, called vacuum freeze-dried, referred to as freeze-dried. The food produced by this method is called freeze-dried food.