Multi-omics insights into floral-fruity aroma formation during Pu'er tea fermentation inoculated with a synthetic fungal community.

Abstract

Pu'er tea fermentation relies on complex microbial activities. This study explored aroma formation in ripe Pu'er tea inoculated with a synthetic fungal consortium using a multi-omics approach across six sampling stages. Sensory evaluation, physicochemical analysis, volatile profiling (HS-SPME-GC×GC-TOFMS), non-volatile metabolomics (UHPLC-Q-Exactive/MS), and metagenomic sequencing were integrated. Inoculation was associated with a distinct floral-fruity aroma. Combined ROAV and VIP analyses identified four volatile compounds, namely phenylethyl alcohol, trans-β-ionone, geraniol, and 1-octen-3-ol, as potentially important aroma-active contributors. Among them, phenylethyl alcohol, trans-β-ionone, and geraniol might play a major role in the floral-fruity character, and their accumulation appeared associated with tea moisture content. Nonanal exhibited a high ROAV but a low VIP value. Non-targeted metabolomics revealed 154 significantly altered metabolites, 38 of which were associated with these volatile compounds. Metagenomic analysis indicated substantial shifts in microbial community structure and function, correlated with physicochemical parameters and volatile profiles. Random forest modeling identified Sphingomonas, Rothia, and Bacteroides as potentially involved in aroma formation. These findings provide insights into the metabolic and microbial dynamics underlying floral-fruity aroma development, offering a scientific basis for tailored starter culture design.