稻谷平衡水分的测定及EMC/ERH等温线方程的选择

Fiting Parameters of EMC/ERH Model for Chinese Rough Rice

采用静态称重法测定7个籼稻和1个粳稻品种的平衡水分,并利用常用的6个EMC/ERH方程（修正BET、修正Chung-Pfost、修正Guggenheim-Anderson-deBoer、修正Henderson、修正Oswin及Strohman-Yoerger）拟合吸附/解吸等温线。在ERH 11.3%~96%范围内,修正Chung-Pfost（MCPE）和Strohman-Yoerger（STYE）拟合最佳。采用含有3个系数、易于转化为M=f（r.h.,t）或r.h.=f（M,t）表达形式的MCPE方程,对8个稻谷品种的吸着等温线进行拟合。以M=f（r.h.,t）形式表达的MCPE方程系数C1、C2、C3,在拟合吸附等温线时分别是784.894、143.337、0.174,在拟合解吸等温线时分别是588.376、59.026、0.180,吸着平均值分别是638.444、87.074、0.177。稻谷吸附与解吸等温线之间存在滞后现象,随着温度增加,滞后环宽度减少。

Equilibrium moisture content（EMC） data for rice grain of eight cultivars were obtained by the gravimetric method at 11% to 96% relative humidity（RH） and 10,20,25,30,and 35℃ above nine saturated salt solutions.Six commonly used mathematic models,BET,Guggenheim–Anderson-deBoer（GAB）,Modified-Chung-Pfost（MCPE）,Modified-Henerson（MHE）,Modified-Oswin（MOE）,and Strohman-Yoerger（STYE）,were fitted to the data with evaluating the coefficient of determination,residue sum-of-squares,standard error of estimate,mean relative percent error,and residual plots.Results： The best-fitted equations to the EMC/ERH data are MCPE and STYE,but MCPE is three-parameter,readily transformed equation and adopted in this study.The three parameters,C1,C2,and C3 of the MCPE in a form of M.=f（r.h.,t）are 784.894,143.337,and 0.174 for adsorption isotherm of rough rice grain,and 588.376,59.026,and 0.180 for desorption isotherm of rough rice grain,respectively.The three parameters,C1,C2,and C3 for average values of desorption and adsorption data are 638.444,87.074,and 0.177,respectively.At a constant RH,EMC decreases with increasing temperature.There are hysteresis loops between desorption isotherms and adsorption isotherms.