Mechanistic insights into aroma aging of ripened Pu-erh tea during long-term storage

Understanding the long-term aroma evolution of ripened Pu-erh tea (RPET) is critical for vintage authentication. Sensory and chemical changes in 23 RPET samples (aged 2 to >40 years) were characterized by QDA, E-nose, HS-SPME/GC × GC-QTOFMS, and GC-O. Sensory profiling revealed a progression from fruity-sweet and pile aromas in young teas toward herbal-woody-stale attributes in aged samples, with a potential integration stage observed at approximately 15-20 years. Among 276 volatiles, 11 robust markers (e.g., 1,2,4-trimethoxybenzene, |r| > 0.8) enabled reliable age prediction. Nineteen key odorants underpinning sensory evolution were identified. Based on correlative evidence, aroma maturation appeared to be associated with carotenoid degradation, lipid oxidation, terpenoid/Maillard transformations, and potential microbial methylation. A sequential microbial methylation pathway converting 1,2,4-trimethoxybenzene to 3,4,5-trimethoxytoluene is tentatively proposed as a possible contributor to pile aroma attenuation and aged aroma formation. This study provides a mechanistic basis for RPET aroma aging and molecular markers for age authentication.