红外辐射干燥胡萝卜切片结构特性研究

Structural Properties Research of Infrared Radiation Drying for Carrot Slices

在不同干燥条件下进行胡萝卜切片红外辐射干燥试验,对表观密度、孔隙率、体积比和体积收缩系数进行了研究。结果表明:表观密度与辐射距离、辐射功率成反比,孔隙率随着含水率的减小而增大,样本厚度与孔隙率成反比,辐射距离与孔隙率成正比,辐射功率在一定范围与孔隙率成正比,超过该范围成反比;为确定适合胡萝卜收缩率和干基含水率比的数学模型,分别基于二次多项式利用线性最小二乘法、指数方程利用非线性最小二乘法对试验数据进行了拟合,得出二次多项式模型拟合较优,能够更好地预测红外干燥过程中胡萝卜收缩率和干基含水率比之间的关系。

Infrared drying experiments were carried out under different drying conditions. The apparent density, porosity, volume ratio variation and volume shrinkage of the dehydrated samples were researched. The experimental results showed that changes of apparent density were proportional to sample thickness in the initial drying process,and the apparent density was inversely proportional to radiation distance and radiation power. The final apparent density of dehydrated carrot was between 1. 01 × 10^3～1. 71 × 10^3 kg / m3. The apparent density of fresh carrot slices was 1. 05 × 10^3 kg / m3. With the decrease of water content,the apparent density increased,and the maximum value was 1. 71 × 10^3 kg / m3. The porosity increased with the decrease of moisture content. Sample thickness was proportional to porosity inversely,and the radiation distance was proportional to porosity,but when the radiation power exceeded a certain range the porosity would decrease. In the whole drying process,the range of the carrot ＇s porosity was between 0. 24 and 0. 62. The sample thickness and radiation power had a significant effect on volume ratio variation and volume shrinkage. The two order polynomial was fitted with the test data by the linear least square method,and the exponential equation was fitted by the nonlinear least square method based on Matlab 7. 0. The maximum determination coefficient R2 of two order polynomial was0. 996 6,the minimum value was 0. 976 2. But the maximum determination coefficient R2 of exponential equation was 0. 960 1,the minimum value was 0. 901 7. The fitting results showed that two order polynomial model was a good fit to predict the relationship between shrinkage and the dry basis ratio of carrot more accurately.