冻融处理对甘薯变温压差膨化干燥动力学的影响

Effects of Freeze-thaw Treatment on Drying Kinetics of Sweet Potato Dried by Explosion Puffing Drying at Variable Temperature and Pressure Difference

为探索冻融处理对甘薯变温压差膨化干燥特性的影响,研究了不同冻融次数和抽真空干燥温度条件下甘薯膨化干燥特性,建立了甘薯变温压差膨化干燥动力学模型。结果表明:冻融甘薯变温压差膨化干燥过程存在加速、等速和降速干燥3个阶段。抽真空干燥温度为85℃时,冻融1、2、3次甘薯膨化干燥需要225、175、250 min;冻融2次,抽真空干燥温度为75、85、95℃时,甘薯膨化干燥分别需要265、175、242 min。冻融甘薯在不同干燥条件下的干燥过程均满足Henderson and Pabis方程,其中待定系数A、k与冻融次数呈立方关系,相关系数R^2为0.999;冻融甘薯在不同干燥条件下的有效水分扩散系数(D_(eff))在3.45×10^(-8)~5.41×10^(-8)m^2/s之间。

The objective of this study was to investigate the effects of freeze- thaw treatment times on sweet potato drying characteristics dried by explosion puffing drying at variable temperature and pressure difference. Effects of freeze- thaw treatment times and different vacuum drying temperature on drying characteristics of sweet potato were compared. The drying kinetics models of sweet potato explosion puffing drying at variable temperature and pressure difference were founded. Results showed there were rising- rate,constant- rate and falling- rate periods in sweet potato explosion puffing drying process. At vacuum drying temperature 85 ℃,sweet potato explosion puffing drying time treated by freeze- thaw treatment once,twice and three times were 225,175 and 250 min,respectively. Drying time of sweet potato explosion puffing treated by freeze- thaw treatment twice at vacuum drying temperature 75,85 and 95 ℃ were 265,175 and 242 min,respectively. Henderson and Pabis model provided better simulation of drying curves for freeze- thaw treatment sweet potato explosion puffing drying at different drying conditions. Fitting undetermined coefficients A and k of Henderson and Pabis were cubic relation with the freeze- thaw treatment times and the coefficient R2 value was 0. 999. The effective moisture diffusivity（ D_（eff）） of freeze- thaw sweet potato dried by explosion puffing drying at variable temperature and pressure difference was among 3. 45 × 10（-8） 5. 41 × 10（-8）m2/s.