Optimization of technical parameters of microwave-vacuum drying of Chinese gooseberry slices

The experiments of microwave-vacuum drying of Chinese gooseberry slices were conducted to improve the drying productivity and the quality of dried fruit, and decrease the drying energy consumption. Through the single factor experiments, the influences of microwave power applied, sample thickness and pressure in drying chamber on the microwave drying characteristics were studied. By using the quadratic regression orthogonal experimental method with three factors and five levels, the relationships between the microwave power applied, the sample thickness, the pressure in drying chamber and the rehydration ratios, chlorophyll and vitamin C retention ratios of dried Chinese gooseberry slices, as well as the energy consumption of drying process, were analyzed, and the regression mathematical models for experimental indices and factors were established. At last, the optimal combination of the parameters for the microwave-vacuum drying technology of Chinese gooseberry slices was obtained through nonlinear optimization method with many targets. They were as follows: drying power of 5.54 W/g, material thickness of 6.16 cm and vacuum pressure of 76.8 Pa. Under these conditions, the higher quality of dried Chinese gooseberry slices can be maintained after drying process, and energy consumption is low.