预干燥含水率对苹果片变温压差膨化干燥特性的影响

Effect of Pre-drying Moisture Content on the Drying Characteristics of Apple Slices during Explosion Puffing Drying

为明确原料含水率对苹果片变温压差膨化干燥特性的影响,研究了6个梯度预干燥样品在干燥过程中水分的扩散情况,并通过模型比较,建立变温压差膨化干燥动力学模型。试验结果表明:变温压差膨化干燥主要为降速干燥,内部水分扩散控制整个干燥过程;Parabolic模型为预测不同预干燥条件下苹果变温压差膨化干燥过程中水分变化的数学模型。干燥过程中有效水分扩散率Deff随预干燥含水率的降低而增大,到达临界含水率时,Deff达到最大值;超过临界值后,Deff随预干燥含水率的降低而降低。

In order to identify the moisture content effect of raw materials on explosion puffing drying（EPD） characteristics of apple slices, the moisture diffusion of six gradient preliminary drying samples were investigated. The EPD kinetics model was established. Results showed that the EPD process was mainly in falling rate period, which was controlled by the internal moisture diffusion; Parabolic model was determined as the forecast model to predict moisture changes under different preliminary drying apples of EPD. The effective moisture diffusivity（Deff） value increased with the decreasing pre-drying moisture content（PDMC）; the highest value of Deff was indicated in the critical value of PDMC; while, the value of Deff dropped with PDMC decreasing when PDMC exceeded the critical value.