Microwave drying of amaranth and quinoa seeds: effects of the power density on the drying time, germination rate and seedling vigour

In this work, the drying of amaranth and quinoa seeds using microwave technology has been studied for the first time. The main objective of this study was to analyze the influence of the power density of the microwave oven on the drying time, germination rate and field survival of these seeds. The tests were performed in a domestic microwave oven at three power densities (0.875, 1.75 and 3.50 W/g for amaranth seeds, and 1.75, 3.50 and 7 W/g for those of quinoa). It was observed that as the power density increased, the germination rate of the amaranth seeds decreased slightly (approximate to 9%), as did the height of the plant (3.5%); whereas their survival rate in the field, 30 days after sowing, remained almost unchanged. In contrast, the germination rate of quinoa seeds was significantly affected by microwave drying at these power densities, with germination percentages of less than 25% being achieved. In order to increase the germination rates of both types of seed, after the drying process, it is necessary to employ power densities of less than 1.75 W/g and, in the case of quinoa seeds, the temperature of the drying process also needs to be carefully controlled.