This study employed a range of indicators, including heat of combustion, combustibility, fat content, amino acid content, ash content, crude fiber content, trace element content, and concentrations of catechins, theanine, and caffeine, to develop comprehensive evaluation systems for assessing the quality of five tea samples: Duyun Maojian tea, Liping fragrant tea, Shuicheng spring tea, Huaxi jasmine tea, and Zunyi black tea. Analytical techniques such as gray pattern recognition (GPR), gray principal component analysis (GPCA), gray factor analysis (GFA), entropy analysis (EA), and factor cluster analysis (FCA) were utilized. Based on the 42variable data, the nutritional value ranked as follows: Shuicheng spring tea > Huaxi jasmine tea > Duyun Maojian tea > Liping fragrant tea > Zunyi black tea. These findings offer significant theoretical and practical insights for the determination and comprehensive evaluation of tea quality indicators, contributing to scientific research on the nutrition, health, and classification aspects of tea.
In this work, solubility data of 1,3-dimethylurea (DMU) in methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, and 1-octanol were measured by synthetic method from T = 288.15 to 328.15 K at ordinary pressure. It turned out that the solubility data increased as temperature and solvent polarity increased. The molecular interactions in solution have been studied by the linear energy relationship. Furthermore, based on two thermodynamic models (i.e., modified Apelblat and Wilson), the experimental results were fitted and analyzed. Finally, the thermodynamic properties of solution, including entropy, enthalpy, and Gibbs energy were calculated. These results indicate that in all selected solvents the dissolution behavior were endothermic, entropy-driven, and not spontaneous.
危险品化学品经营许可证（带存储）