Investigation of the classification criteria and flavor compounds in diversified commercially ripened Pu-erh teas

Commercially ripened Pu-erh teas (CRPTs) exhibit a complex flavor profile that poses challenges to standardized production. This study combines traditional sensory evaluation with electronic tongue technology to assess the overall flavor and taste attributes of CRPTs both qualitatively and quantitatively. Multivariate statistical techniques, including Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA), and Partial Least Squares Discriminant Analysis (PLS-DA), were used to classify the samples into four categories: Heavy and Thick (HT_CRPT), Heavy and Mellow (HM_CRPT), Mellow and Thick (MT_CRPT), and Mellow and Light (ML_CRPT). HT_CRPT exhibits the highest richness, HM_CRPT demonstrates the greatest astringency and aftertaste-A with the least sweetness (p < 0.05), MT_CRPT presents the most umami and the least richness, while ML_CRPT has the lowest levels of astringency, umami, and bitterness (p < 0.05). CRPTs vary in liquid color from brownish-red to reddish-brown, with HM_CRPT exhibiting the darkest hue, characterized by L* and a* values of 56.15 ± 2.56 and 30.93 ± 1.85, respectively. The principal chemical components of CRPTs encompass theabrownins, phenylpropanoids, polyketides, lipids, and lipid-like molecules. A total of 282 metabolites, including (-)-Epigallocatechin 3,4'-di-gallate, flavonol 3-O-D-glucoside, and isorhamnetin 4'-O-glucuronide significantly influence the flavor of CRPTs (VIP > 1 and p < 0.05). 24 and 35 components underlie liquid color and taste, respectively, with taste compounds interacting with taste receptors primarily through van der Waals forces and hydrogen bonding. A flavor wheel was developed to illustrate in detail the classification criteria and flavor compounds of various CRPTs. The findings establish a scientific foundation for the development of a standardized evaluation system for CRPTs and the creation of a diverse range of products.