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Solar drying of Stevia (Rebaudiana Bertoni) leaves using direct and indirect technologies

机译:使用直接和间接技术对甜叶菊(Rebaudiana Bertoni)叶片进行太阳能干燥

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The Stevia plant has acquired great importance and has increased its consumption in the world, because it is a great natural sweetener, up to 300 times than sugar. Its higher sweetening content occurs mainly in dry leaves, being important to analyze the drying process. In a previous study they were not found works related to solar drying of the Stevia. In this work, experimental dehydration of the Stevia leaves using direct (cabinet type) operating at natural and forced convection and indirect (air heated by a solar water heating system) as solar drying technologies is presented. The experimental results demonstrated the technical feasibility for the solar drying of Stevia leaves. Indirect solar drying was observed to have superior conditions, moderate drying times, better control of the operating conditions and greater protection against the effects of temperature compared with direct exposure to solar radiation, drying kinetics were highly similar between samples, and equilibrium was reached between 240 min and 270 min. Colorimetric analyses indicate that the effect of temperature is the most significant parameter on tone degradation. Integrating the shadow-mesh cover in the direct solar dryer improved the final quality of the leaves, reduced the discoloration effect, with the mesh-shadow cover, natural convection yielded a drying time of 360 min and forced convection had a drying time between 550 min and 600 min. Without mesh, these values were 250 min and 300 min, respectively. The Weibull and Two-term exponential models for direct solar drying and Weibull model for indirect solar drying were the best fit to the experimental results. The analyzed solar drying technologies will allow to obtain important savings of conventional energy with a smaller environmental impact and a better quality of the final product in relation to the traditional methods of drying.
机译:甜叶菊植物非常重要,并且在世界范围内的消费量增加,因为它是一种天然的甜味剂,是糖的300倍之多。其较高的甜味含量主要出现在干叶中,对于分析干燥过程很重要。在以前的研究中,他们没有发现与甜叶菊太阳能干燥有关的作品。在这项工作中,介绍了使用自然对流和强制对流操作的直接(柜式)和间接(通过太阳能热水系统加热的空气)作为太阳能干燥技术对甜叶菊叶片进行的实验脱水。实验结果证明了甜叶菊叶片太阳干燥的技术可行性。与直接暴露于太阳辐射相比,观察到间接太阳干燥具有更好的条件,适中的干燥时间,更好的操作条件控制以及对温度影响的更好的保护,样品之间的干燥动力学非常相似,并且在240之间达到平衡分钟和270分钟。比色分析表明温度的影响是色调降低的最重要参数。将阴影网罩集成到直接太阳能干燥器中可改善叶片的最终质量,降低褪色效果,使用网状阴影罩,自然对流可产生360分钟的干燥时间,强制对流的干燥时间介于550分钟之间600分钟如果没有网格,则这些值分别为250分钟和300分钟。直接太阳干燥的Weibull和二项指数模型和间接太阳干燥的Weibull模型最适合实验结果。与传统的干燥方法相比,经过分析的太阳能干燥技术将可以节省大量常规能源,对环境的影响较小,最终产品的质量更好。

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