Heat Uniformity Study and Viability of Red Lentil at Different Seed Moisture Contents after Low-Dose Microwave Treatment

Abstract

Abstract. Microwave processing has recently gained attention for seed treatment to eradicate pests and pathogens. However, there is a lack of data on the effect of microwave treatment on legume viability, as well as heat uniformity after microwave treatment. To clarify this matter, 50 g of red lentils at four moisture contents (MC) from 9% to 21% wet basis (w.b.) were treated in a microwave oven with full output power of 1100 W (producer information) or 3.33 W g-1 (based on calorimetric method) at power levels of 30%, 40%, and 50% and exposure times of 30 and 60 s. Final temperature distribution was captured using an infrared thermal camera, and absorbed power (W g-1) and energy (J g-1) were calculated using thermal properties of lentil. Lentil viability was negatively affected at absorbed energy higher than 70 J g-1 at any moisture content. For high moisture contents, more than 70 J g-1 were absorbed at power levels of 40% and 50% after 60 s exposure time. However, the viability of dry lentils was not affected after exposure to 50% power for 60 s, which raised the average temperature to 55°C. Germination and vigor of lentil at 21% MC treated with 30% power for 30 s increased by 8.6% and 20%, respectively, and conductivity after two months storage decreased by 15%, which shows the stimulating effect of microwave on lentil seeds. Keywords: Disinfection, Heat uniformity, Legume, Lentil, Microwave, Quality, Seed enhancement, Temperature distribution, Viability.