Decoding long-term aging of ripened Pu-erh tea: sensory equilibrium, metabolic pathways, and chemical markers

Natural storage promotes Ripened Pu-erh tea (RPET) aging along with chemical conversion and flavor evolution. Analysis of teas aged 2-40+ years via sensory evaluation, E-tongue, and untargeted metabolomics showed a rise-fall-stabilization pattern in sensory profiles and metabolites. The 15-year sample reached sensory equilibrium with mild bitterness and enhanced sweetness and mellowness. A total of 313 non-volatile metabolites were identified: early accumulation of amino acids, nucleosides, and catechins; mid-stage depletion via oxidation and hydrolysis; and late-stage stabilization of lipids, phenolic acids, and antioxidants. Lipid oxidation products mitigated bitterness, while amino acids, nucleotides, and phenolic derivatives enhanced sweetness, kokumi, and flavor complexity. Fourteen age-dependent metabolites, including α-linolenic acid and L-phenylalaninol, correlated with storage duration strongly. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment highlighted flavonoid degradation, nucleotide turnover, and lipid remodeling as key pathways underlying sensory evolution. These findings provide mechanistic insight and objective markers for RPET quality assessment and storage authentication.