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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 (∼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. [ABSTRACT FROM AUTHOR]

In this work, the microwave drying of amaranth seeds at different temperatures has been studied. The main objective of this study is to evaluate the effect of temperature on three key variables of the drying process and viability of amaranth seeds (drying time, energy consumption, and germination rate) after drying with microwave energy. The tests were performed in a domestic microwave oven, modified for research use, at six drying temperatures (between 35 and 60 °C). For comparative purposes, the amaranth seeds were dried by forced convection of hot air in an electric oven. It was observed that an increase in the drying temperature causes a simultaneous decrease in drying time (from 378 to 126 min) and in the energy consumption (from 9.07 to 2.61 Wh g−1, and from 412.6 to 111.7 MJ kg−1 [H 2 O]) and cost (from $0.065 to 0.019 USD) required to dry the seeds. However, there is also an unacceptable decrease (from ∼85% up to 23%) in the germination rate of the seeds with the drying temperature. In order to ensure the amaranth seeds' viability after the drying process, it is necessary to employ lower drying temperatures-i.e., between 35 and 40 °C. Moreover, drying of amaranth seeds with microwave energy at 40 °C proved to be a faster and more effective method than convective drying by reducing drying time by 22% (from 336 min to 261 min) and energy consumption by 74% (from 928.4 to 274.0 MJ kg−1 [H 2 O]) without significantly affecting their viability. [Display omitted] • Microwave drying of amaranth seeds at different temperatures has been studied. • Temperature exerts a significant influence on the process and seeds' viability. • Higher temperatures favor the drying process but significantly impair the viability. • Microwave drying is a faster and more efficient method than convective drying. • Microwave drying, at controlled temperature, could be a viable alternative. [ABSTRACT FROM AUTHOR]