Quality Evolution of Pu-Erh Raw Tea over 1-22 Years of Aging

Long-term aging transforms the sensory quality of raw Pu-erh tea, but the temporal coordination between taste-related and aroma-active compounds remains unclear. Here, raw Pu-erh teas aged for 1-22 years, produced in the same region and stored under consistent conditions, were characterized using sensory evaluation, targeted analysis of non-volatile constituents, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry, relative odor activity values (ROAVs), and multivariate statistics. Aging shifted the sensory profile from fresh, strong, and astringent to mellow and aged, accompanied by a change in liquor color from yellow-green to orange-red. Non-volatile profiles resolved four aging stages (1-4, 6-10, 14-18, and 19-22 years), whereas key aroma-active compounds resolved three stages (1-10, 14-19, and 20-22 years). Tea polyphenols, catechins, and free amino acids generally declined, while theabrownins, thearubigins, gallic acid, and selected flavonoids accumulated. Among 523 detected volatile compounds, 39 exhibited ROAVs ≥ 1; β-ionone and (E)-2-nonenal formed a persistent floral-woody aroma backbone, while stage-specific changes increasingly favored resinous, camphoraceous, roasted, and aged notes. Notably, differences in non-volatile composition weakened after 14 years, whereas aroma profiles continued to reorganize. This asynchronous evolution constitutes the central finding of this study, demonstrating that taste-related composition approaches relative stability before aroma maturation is complete and providing a chemical basis for aging-stage classification and quality evaluation.