Sensory and Metabolomic Analysis Reveal the Quality Evolution of Liupao Tea During Long-Term Aging

Liupao tea develops characteristic sensory properties during aging. However, the evolution of non-volatile metabolites and their relationship with sensory quality remain unclear. Here, three samples aged for 8, 13, and 20 years were analyzed using electronic tongue, colorimetry, and metabolomics. Tea liquor brightness (L*) increased with aging, whereas redness (a*) and yellowness (b*) decreased. Strong correlations between taste and color were observed. Catechins and free amino acids peaked at the intermediate stage, while alkaloids varied, with caffeine remaining stable. A total of 1897 metabolites were identified, with flavonoids increasing and terpenoids and lipids decreasing during aging. The intermediate stage represented a critical transition point with metabolic reprogramming. Key sensory-related metabolites included theobromine, glutamic acid, and theanine (associated with umami, sweetness, and color), as well as gallocatechin gallate, catechin gallate, theacrine, aspartic acid, and arginine (linked to bitterness and yellowness). Flavonoid- and terpenoid-rich modules were also identified. All samples were from a single producer and may not represent all Liupao teas. Overall, this study reveals coordinated changes in sensory quality and metabolites during Liupao tea aging.