Discriminant Analysis of Pu-Erh Tea of Different Raw Materials Based on Phytochemicals Using Chemometrics.

Pu-erh tea processed from the sun-dried green tea leaves can be divided into ancient tea (AT) and terrace tea (TT) according to the source of raw material. However, their similar appearance makes AT present low market identification, resulting in a disruption in the tea market rules of fair trade. Therefore, this study analyzed the classification by principal component analysis/hierarchical clustering analysis and conducted the discriminant model through stepwise Fisher discriminant analysis and decision tree analysis based on the contents of water extract, phenolic components, alkaloid, and amino acids, aiming to investigate whether phytochemicals coupled with chemometric analyses distinguish AT and TT. Results showed that there were good separations between AT and TT, which was caused by 16 components with significant (p < 0.05) differences. The discriminant model of AT and TT was established based on six discriminant variables including water extract, (+)-catechin, (−)-epicatechin, (−)-epigallocatechin, theacrine, and theanine. Among them, water extract comprised multiple soluble solids, representing the thickness of tea infusion. The model had good generalization capability with 100% of performance indexes according to scores of the training set and model set. In conclusion, phytochemicals coupled with chemometrics analyses are a good approach for the identification of different raw materials.

Lexicon development and quantitative descriptive analysis of Hunan fuzhuan brick tea infusion.

Twenty-seven representative Hunan fuzhuan brick teas were collected to develop a terminology lexicon and a quantitative descriptive analysis (QDA) method suitable for the sensory evaluation of Hunan fuzhuan brick tea infusion. Ten trained panelists developed a terminology lexicon comprised of eleven aroma and six taste attributes and evaluated the intensities of sensory attributes of each sample by conducting the QDA method. The QDA results showed that seventeen attributes listed in the final lexicon can be used to evaluate the quality of Hunan fuzhuan brick tea infusion properly, among which five aroma attributes, overall aroma, smoky, floral, fermented, and sweet (fruit), and one taste attribute, bitter, were the characteristic attributes to distinguish the differences in the sample qualities. Another panel made up of four professional cuppers evaluated samples by the cupping method to analyze the applicability and accuracy of the lexicon and the QDA method. The results showed that both the cupping method and QDA can be effectively used to evaluate Hunan fuzhuan brick tea quality, and their evaluation results showed high consistency and mutual complementation. This information will be beneficial for developing a sensory evaluation method and quality control for Hunan fuzhuan brick tea.