Analysis of Tieguanyin aged aroma compounds and their correlation with microbial communities

Aged Tieguanyin has a unique, long-lasting aged aroma. However, a lack of research has hindered further improvements in its quality. This study analyzed the compounds contributing to the aroma of Tieguanyin at different aging times and correlated the results with microorganisms to explore the underlying aging mechanism, using headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS) and MiSeq methods. A total of 85 volatile compounds were identified. The volatiles in tea aged for over 11 years were stable, similar, and significantly different from those of unaged tea. The 13 upregulated discriminatory volatiles in the late aging period were speculated to be the characteristic compounds constituting the aged aroma: 2-heptanone, 2-nonanone, 6,10-Dimethylundecan-2-one, dehydro-β-ionone, β-ionone epoxide, (−)-α-terpineol, 1-octen-3-ol, linalool oxide (II), propanoic acid, butanoic acid, 5-hydroxymethylfurfural, safranal, and caffeine. These compounds are mainly produced through the enzymatic degradation pathway of carotenoids, glycosides hydrolysis, and lipids oxidation. Based on Spearman's correlation analysis, bacteria and fungi had strong interactions with aged aroma compounds. Specifically, Sphingomonas, Acinetobacter, Halomonas, Trichosporon, Aspergillus, and Cyberlindnera were the core functional microorganisms of aged Tieguanyin. These genera had the potential to promote the formation of aged aroma through the accumulation of metabolic precursors.