干燥动力学结合低场核磁共振和物性分析技术的地黄饮片干燥过程表征

Characterization of drying process of Rehmanniae Radix decoction pieces based on drying kinetics combined with LF-NMR/MRI and TA-HD plus

目的 研究地黄饮片干燥特性,量化表征地黄饮片干燥过程,为阐明地黄饮片干燥机制和优化干燥工艺提供依据。方法 选择70、80、90℃3个干燥温度,分别建立地黄饮片干燥过程的动力学模型,分别采用低场核磁共振和物性分析技术研究地黄饮片干燥过程中水的相态分布和质构特性的变化,采用HPLC法动态跟踪干燥过程中指标成分的含量变化。结果Page模型可以准确描述地黄饮片干燥过程中含水量变化,水分比变化随干燥温度升高而加快,模型中干燥常数k随干燥温度的升高而增大,干燥常数n随着干燥温度的升高而减小。干燥过程中水分由外而内逐渐散失,水的相态会发生显著变化,前4 h自由水比例由干燥开始时的93.667%减少至0.329%,束缚水比例由0.985%增加至92.966%,不易流动水比例先增后降,前后变化不明显。硬度、压缩循环功等物性指标在前4 h内随干燥时间增加无明显变化,4 h后各物性指标明显增加。地黄饮片含量测定的6个指标成分中,只有梓醇含量随干燥时间的增加而减少,其他成分变化不明显。结论 采用干燥动力学模型、低场核磁共振和物性分析技术可以直观量化表征地黄饮片干燥过程,为阐明地黄饮片干燥机制和干燥工艺参数的优选提供了科学依据。

Objective The research aimed to study the drying characteristics of Dihuang(Rehmanniae Radix) decoction pieces,quantify the drying process of it, and provide basis for clarifying the drying mechanism and optimizing the drying process of Rehmanniae Radix decoction pieces. Methods The drying temperature of 70, 80, and 90 ℃ was selected to establish the dynamic model of the drying process of Rehmanniae Radix decoction pieces. Low-field nuclear magnetic resonance and imaging(LFNMR/MRI) and Texture Analyser(TA-HD plus) were used to study the phase and distribution changes of moisture during the drying process and the changes of texture characteristics, respectively. And HPLC was used to dynamically track the changes of index components in the drying process. Results Page model could accurately describe the moisture change in the drying process of Rehmanniae Radix decoction pieces, the moisture ratio change rate increased with the drying temperature, the drying constant k increased with the increase of drying temperature, the drying constant n decreased with the increase of drying temperature. During the drying process, water dissipated from outside to inside gradually, and the proportion of moisture phase changed significantly. Within 4h, the free water proportion decreased from 93.667% to 0.329%. The bound water proportion increased from 0.985% to 92.966%. The proportion of uneasily flowing water increased first and then decreases, and the change was not obvious. Within 4 h, the texture properties did not change significantly with the increase of drying time. After 4 h, the texture properties increased sharply. Among the six components for content determination, only catalpol decreased with the increase of drying time, other components did not change significantly. Conclusion Drying kinetics model, LF-NMR/MRI and texture properties analysis techniques could be used to characterise the drying process of Rehmanniae Radix decoction pieces intuitively and quantitatively, which provides a scientific basis for clarifying the drying mechanism and optimizing the drying process parameters of Rehmanniae Radix decoction pieces.