当归切片远红外干燥特性及动力学研究

Far infrared drying characteristics and kinetics of Angelicae Sinensis Radix slices

目的 以当归切片为研究对象,探索当归切片的远红外干燥特性及动力学模型,为提高干制品品质,建立当归科学适宜的产地加工方法提供理论依据。方法 将远红外加热技术应用于当归切片干燥,研究不同干燥温度、切片厚度和辐照高度条件下,当归切片的远红外干燥特性和干制品品质的变化规律,并利用Weibull函数拟合干燥曲线,建立试验因素和模型参数的定量关系。结果 随着干燥温度的增加,切片厚度和辐照高度的降低,水分比明显减小,干燥速率显著增加;当归切片的远红外干燥过程服从Weibull分布函数(R2=0.983 34~0.999 34,χ2=0.001 3~0.006 5),尺寸参数和形状参数均与干燥温度、切片厚度和辐照高度有关;估算水分扩散系数(Dcal)的区间为4.698×10-11~2.084×10-10m2/s,有效水分扩散系数(Deff)的区间为3.891×10-9~2.179 2×10-8 m2/s,均随着干燥温度和切片厚度的增加,辐照高度的减少,总体呈现上升的趋势;与热风干燥的干制品相比,远红外干制品的色差值和水活度更小,更容易保留当归中的阿魏酸和挥发油;对不同干燥条件下干制品微观结构的扫描电镜分析发现,远红外可以增加当归切片内部的微孔数量,细胞排列更加整齐,增加了干燥过程的热质迁移速率,缩短了干燥时间。结论 Weibull分布函数可预测当归切片干燥过程的水分迁移规律,对于当归切片干燥过程的预测和工艺优化具有重要意义。

Objective Taking Angelicae Sinensis Radix(ASR)slices as the research object,the far infrared drying characteristics and kinetic model of ASR slice were explored,which provided a theoretical basis for improving the quality of dry products and establishing a suitable processing method.Methods The far-infrared drying technique was applied to the drying of ASR.The far-infrared drying characteristics and dry product quality of ASR were studied under different drying temperature,slice thickness and irradiation height,and the Weibull function was used to fit the drying curve.The quantitative relationship between test factors and model parameters were established.Results With the increase of drying temperature and the decrease of the slice thickness and the irradiation height,the water ratio was decreased significantly,and the drying rate was increased significantly.The far-infrared drying process of the ASR slice obeyed the Weibull distribution function(R2=0.983 34—0.999 34,χ2=0.001 3—0.006 5),both the size parameter and the shape parameter were related to the drying temperature,slice thickness and irradiation height;The interval for estimating the water diffusion coefficient(Dcal)was 4.698×10-11—2.084×10-10 m2/s.The effective moisture diffusion coefficient(Deff)was in the range of 3.891×10-9—2.179 2×10-8 m2/s,both of which tended to increase with the increase of drying temperature,slice thickness and irradiation height.Compared with dry products from hot-hair drying,the color difference and water activity of far infrared drying were smaller,and it was easier to retain ferulic acid and volatile oil in ASR.Scanning electron microscopy analysis of the microstructure of dry products under different drying conditions showed that far infrared increased the interior of ASR slices.The number of micropores was increased,the cells were arranged more neatly,so as to increase the rate of thermal mass migration during the drying process and reduce the drying time.Conclusion The Weibull distribution function can predict the water migration law of the drying process of ASR.It is of great significance for the prediction of the drying process of ASR and the process optimization.