Development of a Microwave System for Highly-Efficient Drying of Fish

Dried fish is an important product of Nakhon Si Thammarat province, located in southern Thailand. Fish are conventionally dried using heat from the sun or heat from burning wood as energy sources. These drying methods have problems such as low efficiency and environmental problems. Exploiting the strong electric dipole of the water molecules in the fish, which allows the fish to absorb microwave energy effectively, we have developed a novel microwave heating system for the efficient drying of fish. The system utilizes a high-voltage power supply so that the magnetron can generate a microwave field continuously, and its output power can be adjusted from 0 - 200 W making it very different to commercial microwave oven. The waveguide is designed for effective transmission of microwave fields into the multi-mode heating cavity. The experimental results reveal that heat produced by the microwave system causes evaporation of moisture from the fish making it possible to produce high quality dried fish. The drying process also shows a dependence of fish surface temperature and moisture content on the radiation time and microwave power.