Drying kinetics of Amaranthus cruentus ‘BRS Alegria’ seeds in natural and artificial methods

ABSTRACT The seeds of most crops are often harvested with water concentrations above the recommended levels; for instance, amaranth crops can be harvested under water contents up to 40%. Therefore, drying of the harvest is essential to preserve its post-harvest quality. Thus, the objective of this study was to investigate the drying kinetics of Amaranthus cruentus ‘BRS Alegria’ seeds dried via natural and artificial methods. Drying experiments were conducted in laboratory under natural methods, in shaded and open sun conditions, and also under artificial drying at temperatures of 60, 80 and 100 °C. The average temperatures of the seed mass were 30, 40, 50, 60, and 70 °C for the natural drying methods, shaded and open sun, and under the artificial drying at temperatures of 60, 80, and 100 °C. The modified Midilli equation proved to be the best model for describing the drying kinetics of Amaranthus cruentus ‘BRS Alegria’ seeds. For the artificial drying method at temperatures of 60, 80, and 100 °C, durations of 2.5, 3.5, and 7 hours were respectively required to reduce the water content from 21.1% to 11.5%; and, 4.25, 4.75, and 10 hours to reduce concentration 21.1% to 8.5%. For natural drying under open sun, a drying time of 15 hours was required; for shaded conditions, a drying time of 164 hours was required until the water concentration reduced to 13% which was the equilibrium moisture.

摘要 大多数作物的种子在收获时的含水量往往高于推荐标准；例如，籽粒苋（Amaranthus cruentus）可在含水量高达40%的状态下完成收获。因此，对收获物进行干燥处理对维持其采后品质至关重要。本研究旨在探究采用自然干燥与人工干燥方式处理的‘BRS Alegria’籽粒苋种子的干燥动力学特性。干燥实验在实验室环境下开展，涵盖自然干燥（包括遮阴与露天日晒两种条件）以及60℃、80℃、100℃三个温度梯度的人工干燥处理。针对自然干燥（遮阴、露天日晒）及60℃、80℃、100℃人工干燥的各组试验，其种子物料的平均温度分别为30℃、40℃、50℃、60℃与70℃。修正的米迪利（Midilli）方程被证实是描述‘BRS Alegria’籽粒苋种子干燥动力学特性的最优模型。在60℃、80℃、100℃的人工干燥条件下，分别耗时2.5小时、3.5小时与7小时，即可将种子含水量从21.1%降至11.5%；而将含水量从21.1%降至8.5%则分别耗时4.25小时、4.75小时与10小时。采用露天日晒自然干燥方式时，需耗时15小时即可达到干燥终点；遮阴自然干燥则需164小时，直至种子含水量降至平衡水分13%。