Microwave Freeze Drying of Apple Slices Based on the Dielectric Properties

摘要

Freeze drying (FD) yields the best quality of dried apple slices but at the cost of long drying time and also the overall cost.Air drying (AD) gives an unacceptably poor quality product. To achieve faster drying along with a high quality product a microwave freeze drying (MFD) technique was developed to dry apple slices. The relationship between corona discharge and microwave power at various pressures and initial moisture content conditions was studied to avoid the possibility of corona discharge during MFD.According to the dielectric properties of apple, a control strategy for the MFD process was also developed.MFD reduced the drying time by about half of conventional FD process and provided a similar good product quality.