目的 基于水分活度（water activity，A_w）和玻璃化转变理论揭示泽泻Alismatis Rhizoma饮片的水分吸附特性，为预测泽泻饮片的水分限度，优化其干燥加工、贮藏工艺提供新的理论依据。方法 采用静态称量法测定泽泻饮片在15、25、35、45 ℃下及A_w 0.11～0.90内水分吸附等温线（moisture sorption isotherms，MSI），选用GAB、BET、Peleg、Henderson、Oswin、Smith、Halsey和Caurie共8个常见吸附模型对吸附数据进行拟合，确定其最佳拟合模型和参数。通过计算吸附过程的净等量吸附热（net equivalent adsorption，q_st）、微分熵和熵-焓互补理论等热力学性质的变化，探讨泽泻饮片水分吸附特性和机制。采用差示扫描量热法测定泽泻饮片的玻璃化转变温度（glass transition temperature，T_g），揭示水分含量对泽泻饮片T_g的影响。通过构建基于水分含量-A_w-T_g的状态图，预测泽泻饮片的水分限度。结果 泽泻（饮片）和盐泽泻的吸附等温线呈“S”形，属于II型等温线，Peleg模型为最佳拟合模型，热力学性质显示2种泽泻饮片的干燥终点应控制在10.00%～15.00%，15.00%易达，其后速率减缓，低于10.00%则耗能骤增；基于状态图分析，当贮藏温度为20 ℃时，泽泻（饮片）水分含量应≤10.17%；盐泽泻水分含量应≤11.08%。结论 食品工业A_w和玻璃化转变理论可运用于泽泻饮片水分限度预测研究，为中药贮藏和加工研究提供了一种新的思路和方法。

Objective To reveal the moisture adsorption characteristics of Zexie (Alismatis Rhizoma, AR) slices based on the water activity (A_w) and glass transition theory, providing a novel theoretical basis for predicting the specified moisture limit and for optimizing the drying process and storage conditions. Methods The moisture sorption isotherms (MSI) of AR slices were determined at 15, 25, 35, and 45 ℃ within a A_w range of 0.11—0.90 using the static gravimetric method. Eight common adsorption models, namely GAB, BET, Peleg, Henderson, Oswin, Smith, Halsey, and Caurie, were employed to fit the adsorption data and to determine the best-fitting model and its parameters. The changes in thermodynamic properties, including the net equivalent adsorption (q_st), differential entropy, and the enthalpy-entropy compensation theory, were calculated to explore the moisture sorption characteristics and mechanisms of AR slices. The glass transition temperature (T_g) of AR slices was measured using differential scanning calorimetry to reveal the effect of moisture content on T_g. A state diagram based on the relationship between moisture content, A_w, and T_g was constructed to predict the specified moisture limit for storage. Results The adsorption isotherms of AR (decoction pieces) and salt-processed AR displayed an S-shaped curve, characteristic of type II isotherms. The Peleg model was identified as the best-fitting model. Thermodynamic analysis indicated that the drying endpoint for both types of slices should be controlled within 10.00%—15.00%. 15.00% is easily reached, drying slows thereafter, and below 10.00% energy consumption rises steeply. Analysis based on the state diagram showed that at a storage temperature of 20 ℃, the moisture content of AR (decoction pieces) should not exceed 10.17%, and that of salt-processed AR should not exceed 11.08%. Conclusion The theories of A_w and glass transition from the food industry can be applied to predict the specified moisture limit of AR slices. This provides a novel approach and methodology for the research on storage and processing of traditional Chinese medicines.

R283.6

国家重点研发计划项目（2024YFC3507001）；成都中医药大学“杏林学者”学科人才科研提升项目（XCZX2022006）