青豆种子等温线及平衡含水率模型

为研究青豆种子的热动力学特性,深入理解青豆吸附过程的水分特性和所需能量变化,利用饱和盐溶液,采用静态称重法测定了青豆种子在20～40,℃和水分活度在0.112～0.946范围的等温线;采用非线性回归方法确定了BET多分子层吸附理论模型的系数,并判定了青豆的吸附与解吸模型的拟合优度;应用Clausius-Clapeyron方程计算了青豆的净等量吸附热.结果表明：吸附与解吸相比存在明显的滞后现象;解吸时单分子层饱和吸附量大于吸附时的数值,随着温度升高青豆的单分子层饱和吸附量下降;吸附层数的变化趋势与单分子层饱和吸附量的相反;在Henderson、修正的Henderson、修正的Chung-Pfost、Halsey、修正的Halsey、修正的Oswin、修正的GAB模型中,Halsey模型拟合优度最佳;净等量吸附热随平衡含水率的增加而减少.

Water Sorption Isotherms and Equilibrium Moisture Content Models for Green Soybean Seeds

In order to investigate thermodynamic properties of green soybean seeds and undersand water properties and energy requierment change associated with the sorption behavior, sorption isotherms of green soybean seeds were determined using the gravimetric static method of saturated salt solution at temperatures in a range of 20--40℃ and water activity from 0.112 to 0.946. BET multilayer sorption theory model coefficients and goodness of fit of ad- sorption and desorption models for green soybean were estimated using nonlinear regression method. The net isosteric heat of sorption was estimated by applying Clasusius-Clapeyron equation to sorption isotherms between 20 and 40℃. Results indicated that there is a notable hysteresis effect between the adsorption and desorption curves and green soybean monolayer saturated adsorptive capacity was greater in desorption process than that in adsorption proc- ess. The monolayer saturated adsorptive capacity decreased with the temperature increment, while the number of multilayer had a reverse trend with the monolayer saturated adsorptive capacity. In the flowing models such as Hen- derson, modified Henderson, modified Chung-Pfost, Halsey, modified Halsey, modified Oswin and modified GAB, Halsey model had a favorable fitting agreement with experiment data and the net isosteric heat of sorption de- creased with the increase of equilibrium moisture content.