Experiment And Study On Vacuum Freeze-drying Technological Parameters Of Fruits And Vegetables

Fruits and vegetables drying technology is an important content of the processing of agricultural products, it is also an important measure which can promote the development of regional specialties agriculture, improve agricultural efficiency and increase farmers’ income. At present, all kinds of fruits and vegetables drying methods have their own advantages, but also have different limitations. This paper made a comparative test with hot-air drying, vacuum drying and vacuum freeze-drying; The test study about the impact of dynamical pressure, constant pressure and different trays on the time of drying, in order to seek a way of improving drying quality, reducing drying energy consumption and optimizing process parameters. The main research contents and conclusions include:(1) The test compared three drying methods of hot-air drying, vacuum drying and vacuum freeze-drying used by drying carrot slices, and analyzed the effect of different drying methods on carrot slices quality.The results showed that vacuum freeze-drying had the least influence on the quality of carrot slices, hot-air drying had the most important influence, and vacuum drying between them.(2) The test was conducted on optimization of parameters for vacuum freeze-drying of Chinese toon by using quadratic regression orthogonal test design, the data was processed by statistical software SAS, it analyzed the effect of heating temperature, the pressure of drying chamber and the size of material on the time of drying and energy consumption of drying.The results indicated that the sequence of factors by effect degree was heating temperature, size of material, pressure of drying chamber; the optimized processing parameters were that heating temperature is90℃, pressure of drying chamber is75Pa, size of material is8mm.(3) The test compared the impact between dynamical pressure and constant pressure on vacuum freeze-drying of banana, as well as the impact of different trays, take energy consumption as the test index. The results showed that compared with constant pressure, the drying time decreased by9s under dynamic pressure, but energy consumption increased by0.01×105J, without any significant difference Compared with ordinary material tray, the drying time increased by7.6s with well plate, energy consumption increased by0.08×105J, and without any significant difference.