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Analysis of Water Adsorption and Thermodynamic Properties of Three Rhei Radix et Rhizoma Decoction Pieces / 中国实验方剂学杂志
Article in Chinese | WPRIM | ID: wpr-872775
Responsible library: WPRO
ABSTRACT

Objective:

To investigate the moisture adsorption and thermodynamic characteristics of raw products, wine-processed products and fried charcoal products of Rhei Radix et Rhizoma, in order to guide their drying and storage.

Method:

Static isotherm weighing method was used to determine the adsorption isotherm curves of three Rhei Radix et Rhizoma decoction pieces at 25, 35, 45 ℃, and the test data were fitted with 7 commonly used water adsorption models to determine the best model for studying the adsorption thermodynamic parameters of these decoction pieces.

Result:

The best adsorption models of these three decoction pieces were all GAB model. At 25, 35, 45 ℃, the absolute safe moisture content of fried charcoal products was 7.43%, 6.79% and 6.20%, of wine-processed products was 8.68%, 8.17% and 7.03%, of raw products was 9.88%, 9.36% and 7.77%, respectively. At 25, 35, 45 ℃, the relative safe moisture content of fried charcoal products was 9.46%, 8.63% and 8.21%, of wine-processed products was 11.49%, 11.03% and 9.74%, of raw products was 13.49%, 12.66% and 11.14%, respectively. The net equivalent heat of adsorption (Qst) and differential entropy (Sd) of these three kinds of decoction pieces all decreased with the increase of equilibrium moisture content, Qst and Sd were in accordance with the entropy-enthalpy complementary theory. The constant velocity temperatures of raw products, wine-processed products and fried charcoal products of Rhei Radix et Rhizoma were 386.66, 391.15, 394.34 K (unit conversion of 1 K=-272.15 ℃), their Gibbs free energies were 0.372 2, 0.406 0, 0.372 2 kJ·mol-1, respectively. Their adsorption processes were an unspontaneous process driven by enthalpy.

Conclusion:

The orders of equilibrium moisture content, monomolecular layer moisture content, Qst and Sd of three Rhei Radix et Rhizoma decoction pieces are all raw products>wine-processed products>fried charcoal products. The moisture absorption capacity of the decoction pieces is ranked as raw products>wine-processed products>fried charcoal products. The frying and roasting process significantly affects the hygroscopicity and thermodynamic properties of the three decoction pieces, the reason for this difference may be that the high temperature of the stir-frying results in the decrease of the hygroscopic groups and the increase of the hydrophobic materials in raw products, and the change in the texture of the decoction pieces. The research on the water adsorption characteristics of three Rhei Radix et Rhizoma decoction pieces can provide reference for selecting their storage conditions and drying process.

Full text: Available Index: WPRIM (Western Pacific) Language: Chinese Journal: Chinese Journal of Experimental Traditional Medical Formulae Year: 2020 Type: Article

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Full text: Available Index: WPRIM (Western Pacific) Language: Chinese Journal: Chinese Journal of Experimental Traditional Medical Formulae Year: 2020 Type: Article