Danial DEHNAD - Department of Food Materials and Process Design Engineering, Faculty of Food Science and Technology, University of Agricultural Sciences and Natural Resources Basidj Square, Pardis, Gorgan, Iran
Seid Mahdi JAFARI - Department of Food Materials and Process Design Engineering, Faculty of Food Science and Technology, University of Agricultural Sciences and Natural Resources Basidj Square, Pardis, Gorgan, Iran

Microwave drying is used instead of conventional hot air drying to reduce drying time and to improve food quality. By combining hot air with microwave method, process of drying is accelerated because volumetric heating, caused by microwave power, drives moisture from the product interior to travel towards the surface, where it is removed by the surrounding heated, moving air. Quality of a microwave dried food can often be improved further by the use of vacuum. In combined microwave-fluidized bed drying, the fluidization provides a pneumatic agitation so that time-averaged microwave radiation can be received by a single particle. Experiments have shown that the microwave freeze-drying appears to be one of the most promising techniques to accelerate the rate of dehydration and enhance product overall quality. Combining infrared with microwaves drying is expected to lead to higher energy efficiency and higher-quality products. Osmotic dehydration prior to microwave dehydration can produce unique products with better taste, stabilize color, improve the texture of the product and flavour characteristics, and increase nutritional value.

Microwave–Freeze Drying, Vacuum-Microwave Drying