Objective

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To analyze the flavor substances and change rules of Rhei Radix et Rhizoma during the process of nine-time repeating steaming and sun-drying.

Method

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The flavor response values of Rhei Radix et Rhizoma samples were obtained by using PEN3 electronic nose system. The data were processed and analyzed by principal component analysis （PCA）， linear discriminant analysis （LDA） and Loadings analysis.

Result

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Rhei Radix et Rhizoma processed with nine-time repeating steaming and sun-drying could be effectively distinguished into two categories as the sixth sample was the turning point. The samples steamed and dried for one to five times could be grouped into one category， the other four samples were obviously distinguished from them. The main flavor components reached the maximum response in the sample processed with six-time repeating steaming and sun-drying， and its response value of inorganic sulfur compounds was about 2.7 times that of the sample processed with one-time repeating steaming and sun-drying. In addition， compared with the raw products， the flavors of Rhei Radix et Rhizoma processed with nine-time repeating steaming and sun-drying and wine stewing changed significantly， and the response value of inorganic sulfur compounds in sample processed with nine-time repeating steaming and sun-drying was about 2.2 times that of raw products. From the perspective of flavor analysis， the response values of inorganic sulfur compounds and nitrogen-oxygen compounds in sample processed with nine-time repeating steaming and sun-drying were higher than those of wine-stewed products， and the two were not completely equivalent.

Conclusion

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Electronic nose technology preliminarily clarifies the dynamic change rules of the flavor of Rhei Radix et Rhizoma during the process of nine-time repeating steaming and sun-drying from the flavor characteristics， and clarifies the difference between products processed with nine-time repeating steaming and sun-drying and wine-stewed products from the odor characteristics， which lays a foundation for revealing the processing principle of Rhei Radix et Rhizoma processed with nine-time repeating steaming and sun-drying.