4种中药浸膏粉等温吸湿规律与吸湿热分析

Isothermal Moisture Absorption Law and Hygroscopic Heat of Four Kinds of Chinese Medicine Extract Powders

摘要:

目的: 研究中药浸膏粉的等温吸湿规律和吸湿热,考察浸膏粉在吸湿过程中的水分变化和能量变化. 方法: 选择大黄、当归、黄芪、菊花的浸膏粉为模型药,运用静态法获取4种浸膏粉在不同温度下的等温吸湿数据,利用6种吸湿模型(GAB,BET,Henderson,Smith,Oswin,Halsey)进行拟合,通过非线性二次回归分析法对拟合的模型进行评价,使用Glausius-Clapeyron方程计算等温吸湿热.采用苯酚硫酸法测定浸膏粉中多糖和寡糖含量作为分析吸湿规律的物质基础. 结果: 在6种吸附模型中,GAB模型拟合度最高(R²≥ 0.999 4),且单分子层含水量随浸膏粉中寡糖含量增加而增加.不同温度下,水分活度小于某一临界值时,平衡含水率随温度升高而降低,而当活度达到一定值时,有1个交叉点,出现了平衡含水率随温度升高而增加的反常现象,4种浸膏粉的交叉点对应水分活度分别0.75,0.65,0.68,0.62.各浸膏粉的吸湿热与水分含量关系密切且随着水分含量的增加而呈下降趋势. 结论: 等温吸湿规律和吸湿热研究量化了中药浸膏粉对环境中水蒸气吸附能力的大小,还能描述吸湿过程中粉末的物理状态,较采用临界相对湿度研究浸膏粉的吸湿性更具创新性,为中药生产和贮藏过程中防潮问题提供参考.

Abstract:

Objective: To study on isothermal moisture absorption law and hygroscopic heat of Chinese medicine extract powders,and inspect on water and energy changes during moisture adsorption process. Method: A static gravimetric method was adopted to obtain isothermal moisture absorption data of Rhei Radix et Rhizoma,Angelicae Sinensis Radix,Astragali Radix and Chrysanthemi Flos extract powder under different temperatures.Six kinds of moisture models (GAB,BET,Henderson,Smith,Oswin and Halsey) were fitted with nonlinear quadratic regression analysis to evaluate fitness of models,isothermal moisture absorption heat were calculated by Clausius-Clapeyron equation.Phenol-sulfuric acid method was adopted to determine contents of polysaccharides and oligosaccharides,which was taken as material basis for analysis of moisture adsorption behavior. Result: In these 6 kinds of models,fitness of GAB model was the highest with R²≥0.999 4,and the monolayer moisture content increased with increasing of oligosaccharides content.Under different temperatures,when water activity was smaller than a critical value,equilibrium moisture content declined with increasing of temperature,when arrived at a certain water activity,there was a crossing point,then equilibrium moisture content increased with increasing of temperature anomaly,corresponding water activities in crossing points of four extract powders were 0.75,0.65,0.68 and 0.62,respectively.Hygroscopic heat and moisture content of each extract powder was closely related,and showed a downward trend with increasing of moisture content. Conclusion: By investigating isothermal moisture absorption law of Chinese medicine extract powder,it can not only quantified adsorption ability of the powder but also describe moisture adsorption process of powder's physical condition.Compared with traditional method of critical relative humidity,this way is more innovative and has theoretical guidance meaning for production and storage problems of Chinese medicine.