At present, an important development trend of food processing technology is to maintain the nutrition and color fragrance of food to the maximum extent, while the choice of drying process and equipment has a great influence on the nutrition and color and fragrance of food products. Food drying has a lot of characteristics associated with "food", it is different from the drying of chemical products, the former need to consider food hygiene, nutritional loss, color and fragrance changes and so on, the drying temperature and time have strict restrictions; dry food is different from the drying of pharmaceutical products, because food is often low value-added products, And drugs are generally high value-added products, the former must consider the economy of the drying process.
Around the "quality and economy", in recent years, food drying technology and equipment has made a lot of progress, and the combination of vacuum and other drying methods or heating technology, giving the vacuum drying equipment a new connotation and vitality. 1. Characteristics of vacuum drying of food vacuum drying is based on the basic principle that the saturated vapor pressure of water is closely related to temperature, in the vacuum state, the boiling point of water is reduced, that is, in the vacuum operation is at low temperature operation, can avoid the destruction of nutrients in the high temperature, at the same time improve the drying speed.
In addition, in the vacuum system, the content of air in the unit volume is lower than the content in the atmosphere, in this relatively hypoxic environment to dry food can reduce or even avoid the opportunity of fat oxidation in food, pigment browning or other oxidation spoilage, so the use of vacuum drying to obtain better food quality. 2. Traditional vacuum drying equipment vacuum drying in food, pharmaceutical, chemical and other industries have a wide range of applications, domestic development and introduction of a variety of vacuum drying equipment, its structural forms are diverse. In the food industry commonly used forms are mainly box-type, double-cone vacuum dryer, belt vacuum dryer and so on. These traditional vacuum drying equipment mainly uses hot air, steam or electricity heating, using heat conduction, convection or radiation principle to transfer heat from the outside to the inside of the material.