Performance Evaluation of a Multi-Magnetron Microwave Rotary Dryer for Tomyum Spices Processing

Abstract

Thailand's famous Tomyum spices ingredient includes galangal, lemongrass, kaffir lime leaves, and chilies, deriving from economic herbs and plants. After harvesting, they will need to be preserved for subsequent use, usually via drying. This research focused on utilizing a multi-magnetron microwave rotary dryer for processing these ingredients, whose energy consumption and quality of products were evaluated. The weight of raw products used was 10 kg for testing. The target final moisture content of the dried products was less than 14% dry basis (dB). The rotational speed of the dryer was adjusted to 20 rpm and air flows used were between 2-2.5 m/s. It was a fund that, drying of galangal showed the lowest energy consumption about 8.40 MJ/kg H2Oevap when using microwave power at 0.76 W/g. The drying rate, drying time, and drying efficiency achieved were 0.98 kg H2Oevap/h, 7 h 30 min, and 26.87%, respectively. Drying of kaffir lime leaves had the highest energy consumption of 12.21 MJ/kg H2Oevap, at the microwave power at 0.32 W/g. The corresponding drying rate, drying time, and drying efficiency obtained were 0.69 kg H2Oevap/h, 5 h, and 18.50%, respectively. In a comparison of color characteristics between the spice ingredients obtained from a commercial community enterprise and this experiment, their products appeared to have similar color characteristics, based on the RHS color chart. The microwave rotary dryer seemed to be a promising option for drying Tomyum spices.