Cinética de secagem em diferentes temperaturas e qualidade de sementes de Amaranthus cruentus BRS alegria

Abstract

The harvest of seeds with a water content above the recommended is often observed in practice, for several species, and for amaranth it is no different. These levels can be close to 40%, thus requiring drying to preserve the physiological quality of the seeds. Drying can be done with natural or artificial ventilation. There are reports that amaranth is resistant to high drying temperatures, maintaining germination above 70%. This is interesting from a technical point of view, as it speeds up the process. Thus, the objective was to study the drying kinetics of Amaranthus cruentus BRS at different temperatures and to evaluate the effect, in addition to the initial water levels and storage times, on the physiological quality of the seeds. Seed mass temperatures of 30, 40, 50, 60 and 70°C were monitored, carried out by natural, shaded and full sun, and artificial drying, in a forced circulation oven for air temperatures of 60, 80 and 100°C, respectively. In addition, two initial water contents (8.44 and 11.48%) and two storage times (63 and 463 days after drying) were analyzed. The drying kinetics of amaranth occurred at a decreasing rate and was strongly influenced by temperature. The modified Midilli model was the one that best fit. The reduction in water content from 21.1 to 11.5% was 2.5, 3.5, and 7 hours for seed mass temperatures of 70, 60 and 50°C, respectively, artificially dried. For natural drying, in full sun (30°C), the time was 15 hours, and for shade it was 164 hours until the water content was 13% (equilibrium humidity). As for the physiological quality of the seeds, in the natural drying, shade (30°C) was better than full sun (40°C). In artificial drying, the temperature in the seed mass of 70°C was harmful. The seeds were better preserved when stored with a water content of 11.48% compared to 8.44%. Both for natural and artificial drying, the increase in temperature affected the quality of the seeds of A. cruentus BRS Alegria, being aggravated with the longer storage time, in low initial water levels.