1.microwave vacuum freeze drying technology of vacuum F […]
1.microwave vacuum freeze drying technology of vacuum Freeze Dry Machine
In recent years, researchers have used microwave radiation as a heat transfer method, combined with high-efficiency microwave radiation heating technology and vacuum freeze-drying technology to establish microwave vacuum freeze-drying technology, mainly using microwave radiation in a frozen state, the electromagnetic energy Converted to the heat energy required for sublimation of moisture in the material. Jiangnan University has developed a microwave Freeze Dry Machine and process. Microwave vacuum freeze-drying technology is used to treat food dehydration thoroughly, which can effectively maintain the quality of food and increase the drying rate by 4 to 20 times. Ma et al. also proved this by experiment. Microwave heating 13mm thick steak, drying time only 4 ~ 6h, and when heated by conduction, the drying time is 11 ~ 13h. However, the disadvantage is that the equipment cost is high, and it is mainly used in high-value foods, and large-scale application is still in the research stage.
2.spray freeze drying technology of
Spray drying and freeze-drying combine to form a new spray freeze-drying technique, first reported in the European patent, which uses a very low temperature of liquid nitrogen to make droplets by directly spraying the material to be dried into liquid nitrogen. The ice powder is quickly formed in liquid nitrogen, and then the product is dried in vacuum freeze-drying. Spray freeze-drying technology is mainly used in the manufacture of powdered medicines and foods. This technology can significantly shorten the freeze-drying time. Huang Lixin used this technology to dry the milk powder, and the time was shortened from 48h to 10h.
3.combined with freeze drying and hot air drying
While fully considering energy consumption and product quality, many researchers have begun to explore the use of joint drying methods to dry food materials, which is the combination of traditional hot air drying and freeze drying technology. Xu Yanyang et al. used vacuum freeze-drying technology combined with hot air drying technology to dry bamboo shoots. The results showed that the combined drying method reduced energy consumption by about 41.0% compared with single freeze drying. Among them, the products with the first hot air and then lyophilized have poor overall quality.