魔芋真空干燥特性及动力学模型的建立

Vacuum drying characteristics and modeling of kinetics for konjac

为了实现魔芋的规模化真空干燥,缩短干燥时间,提高脱水制品的品质,降低生产能耗和成本。该文采用真空干燥技术将其干燥至安全含水率15%,选取温度(50、60、70℃)和真空度(0.04、0.05、0.06 MPa)为试验因素进行研究,考察了温度和真空度对魔芋切片干燥水分比MR和干燥速率DR的影响、水分扩散系数以及干燥活化能。利用6种常见食品干燥数学模型对实验数据进行非线性拟合,通过比较评价决定系数R^2、卡方χ~2、和标准误差eRMSE以及平均相对误差E得到较优模型模型并与BP神经网络模型进行对比检验。结果表明,魔芋切片真空干燥是内部水分扩散控制的降速干燥过程;魔芋真空干燥最佳动力学模型为BP神经网络模型,模型平均相对误差E为1.32%;在不同干燥条件下对魔芋有效扩散系数Deff和活化能Ea进行求解表明,有效水分扩散系数Deff与真空度和温度成正比,平均干燥活化能E_a为28.96 k J/mol。

The vacuum drying technology was adopted to dry konjac slices to shorten the drying time for konjac large-scale operation. The initial moisture content of konjac is approximately 80% - 85% , and this has to be reduced to below 15% for its long term storage. Drying characteristics of konjac slices, the effective moisture diffusion coefficient and the activation energy were investigated under varying conditions of drying temperature （50,60 and 70℃） and vacuum degrees （0.04,0.05 and 0.06 MPa）. Different drying models were compared by the value of E,R2,X2 and eKMSE. The best model was then compared with BP neural network model. The results showed that BP neural network was the best and E value of the network was 1.32%. The drying process of konjac is a controlled internal water diffusion and reduced dying process. The effective moisture diffusion coefficient Deff and the activation energy Eawere calculated under different drying conditions. The results showed that Doff is proportional to the vacuum and drying temperature, the average value of Ea was 28.96 kJ/mol.