Effect of temperature and slice thickness on drying kinetics of hot- air drying of hawthorn slices
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摘要: 在本研究中,为了探讨热风温度和切片厚度对山楂热风干制动力学的影响,将厚度为2 mm和4 mm的山楂切片置于5090℃的热风干燥箱内进行干制处理,并采用5种常见食品薄层干燥模型对实验数据进行非线性拟合,通过比较评价决定系数（R2）、卡方（χ2）和均方根误差（RMSE）等统计数据确定山楂切片薄层热风干燥过程的最优模型。结果表明:山楂切片薄层热风干燥是内部水分扩散控制的降速干燥过程。Page模型是描述山楂切片薄层热风干燥过程的最优模型。不同干燥条件下有效水分扩散系数Deff和活化能Ea的求解结果表明,有效水分扩散系数Deff随热风温度和切片厚度的增加而增加,在干制温度范围内有效扩散系数的值在2.69×10-1116.12×10-11m2/s之间变化。对于切片厚度为2 mm和4 mm的山楂切片,活化能Ea分别为20.43、26.25 k J/mol。Abstract: In this study,hawthorn slices were dried as thin- layers with thickness of 2 mm and 4 mm in the ranges of50~90 ℃ of drying temperature in a hot- air dryer. The effect of drying hot- air temperature and slice thickness on the drying kinetics was analyzed.Five different dynamic models were fitted nonlinearly by using the drying test data of hawthorn slices and the best suitable model was selected by comparing the values of the correlation coefficient( R2),the reduced chi- square( χ2) and the root mean square error( RMSE).The results showed that drying process of hawthorn slices occurred in the falling rate period,and the moisture transfer was controlled by internal diffusion.The Page model was the best suitable to descript the relationship of hawthorn slices moisture and drying time by hot- air drying.The effective moisture diffusion coefficient( Deff) and the activation energy( Ea) were also obtained by experiments under different conditions,the values of Deff was increased with the addition of drying temperature and slices thickness,and Deffvalues changed from 2.69 × 10-11m2/ s to 16.12 × 10-11m2/ s within the given temperature range.An Arrhenius relation with Eavalues of 20.43 k J / mol and 26.25 k J / mol for the thickness of2 mm and 4 mm expressed the effect of temperature and sample thickness on the diffusivity.
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