基于Weibull函数的烤烟干筋期干燥动力学及颜色分析

　　摘要：【目的】分析干筋期烤烟主脉干燥特性和颜色变化，为干筋期烤烟烘烤工艺优化提供参考。【方法】以云烟87中部叶为试验材料，利用Weibull分布函数研究干筋期不同风速（低速、中速和高速）、相对湿度（12%、18%和24%）和干球温度（60、64、68和72 ℃）条件下烟叶主脉的干燥特性，并对烤后烟叶颜色参数值进行分析。【结果】干筋期烟叶主脉失水呈降速干燥，随着干筋期风速的增加、相对湿度的降低或干球温度的升高，干燥速率加快。利用Weibull分布函数可很好地描述干筋期烟叶主脉水分干燥曲线，尺度参数α随着风速的增加、干球温度的升高和相对湿度的降低而降低，形状参数β受干筋条件影响较小。基于Weibull分布函数的干筋期烟叶主脉估算水分扩散系数Dcal在1.994×10-10～4.026×10-1 m2/s，干筋期烟叶主脉干燥活化能Ea为56.57 kJ/mol。随着干筋期风速增加，烟叶亮度L*和正反面亮度差?L*增大，颜色偏亮黄色；随着干筋期相对湿度的增加，烟叶L*和正反面?L*减小，而红度a*、黄度b*和饱和度C*逐渐增大，颜色偏橘黄色；随着干筋期干球温度的升高，烟叶a*增大，颜色偏红棕色。【结论】烤烟干筋期采用较高的温湿度和较低的风速有利于提高干筋效率、增加烟叶饱和度。
　　关键词： Weibull函数；干筋期；干燥特性；颜色值
　　中图分类号：S572 文献标志码：A 文章编号：2095-1191（2018）02-0333-07
　　Abstract：【Objective】In order to provide a theoretical reference for the optimization of curing process during stem drying stage， the changes of drying characteristics and color of tobacco midrib during stem drying stage was analyzed.【Method】In this study， the middle leaves of Yunyan 87 were used as experimental materials. Weibull distribution function was applied to analyze the drying characteristics of midrib during stem drying stage under different drying air velocities （low velocity， intermediate velocity and high velocity）， relative humidity（12%， 18% and 24%） and dry-bulb temperature（60， 64， 68 and 72 ℃），and the color parameters of flue-cured tobacco leaves were also studied. 【Result】The moisture dehydration of tobacco midrib was in a falling-rate drying process during stem drying stage， its drying rate was increased with the raise of air velocity， decrease of humidity or increase of dry bulb temperature. Weibull distribution function could well describe the drying curves of tobacco midrib during stem drying stage. It was found that the scale parameter α decreased as air velocity increased， humidity decreased and dry bulb temperature increased. And there was a lower influence on the shape parameter β under different stem drying conditions.The moisture diffusion coefficient Dcal of tobacco midrib during stem drying stage based on Weibull distribution was between 1.994×10-10 and 4.026×10-10 m2/s. The activation energy Ea for drying of tobacco midrib was 56.57 kJ/mol. The brightness value L*， the color difference between the front and back of leaves ?L* increased with the increase of air velocity， the color of tobacco leaves was bright yellow. The brightness value L* and the color difference between front and back of leaves ?L* decreased with the increase of relative humidity， while the redness value a*， yellowness value b* and color saturation C* increased gradually， the color of tobacco leaves was close to orange. In addition， the redness value a* increased with the raise of dry bulb temperature， the color of tobacco leaves was reddish brown. 【Conclusion】High temperature， high humidity and low air velocity during tobacco stem drying stage is benefit for improving the drying efficiency and increasing the color saturation of tobacco leaves.

相关热词搜索：烤烟 动力学 函数 干燥 颜色