三七提取物吸湿性及其数学模型研究

Study on Hygroscopicity and Mathematical Models of Panax notoginseng Extract

目的:筛选可准确描述三七提取物吸湿过程的数学模型,科学量化吸湿过程。方法:25、35和45℃下,用重量法测试三七提取物吸湿过程动力学曲线和吸附/解吸等温线,并用1stOpt统计分析软件进行拟合,以均方根误差(RMSE),残差平方和(RSS)和决定系数(R^2)为评价指标,筛选最佳拟合模型,结合25、35和45℃下吸附等温线计算吸附热。结果:25、35和45℃下,三七提取物吸湿动力学双指数模型、吸附/解吸等温线Peleg模型拟合效果较好,吸附/解吸等温线都属于第Ⅱ种类型,解吸等温线因较高的平衡含水量而出现明显的滞后现象,该滞后现象属于H3型。随着温度升高这种滞后现象变弱。吸附热随着平衡吸湿量的增大而增大。结论:双指数模型和Peleg模型分别较好地拟合三七提取物的吸湿动力学曲线及吸附/解吸等温线,且吸附/解吸等温线存在滞后现象,该滞后现象随温度升高而变弱,吸附热与平衡吸湿量密切相关。

Objective:To optimize the mathematical model which could describe the moisture adsorption process of Panax notoginseng extract and to quantify the adsorption process scientifically.Methods:Under 25,35,45 ℃,moisture adsorption kinetics curve,adsorption and desorption isotherms of Panax notoginseng extract were determined by gravimetric method,and the experimental data were fit by the 1 stOpt statistical analysis software package.Comparisons were evaluated with the root mean square error(RMSE),residual sum of squares(RSS)and coefficient of determination(R^2).The heat of adsorption was calculated by adsorption isotherm of 25,35 and 45 ℃.Results:The double exponential model was suitable for fitting moisture adsorption kinetics curve,and the Peleg model was best fitted for adsorption and desorption isotherms which were belong to type II behavior.Compared with the adsorption isotherm,the equilibrium water content of the desorption isotherm was higher,which was called hysteresis and the hysteresis loop was belong to type H3.With the increasing of temperature,the hysteresis becomes weak and the heat of adsorption increases with the increase of equilibrium moisture content.Conclusion:The double exponential model and Peleg model are suitable for fitting the moisture adsorption kinetics curve,the adsorption and desorption isotherms,respectively,and the isotherms exhibit an obvious hysteresis effect which becomes weak with the increase of temperature.The heat of adsorption is closely related to the equilibrium moisture content.