Homologous divergence: Processing reshapes metabolite variations and relative odor activity values in black and green teas derived from Gougunao no. 2

Using leaves from a single origin and the same harvest batch, processing was the sole variable: homologous Gougunao No. 2 green and black teas were produced. An integrated workflow (UHPLC–HRMS and HS-SPME–GC–MS) was combined with flavonoid contents and multiple antioxidant assays to probe how processing reshapes the composition–function–aroma nexus. Multivariate analysis clearly separated the two teas, with green tea showing higher flavonoids and stronger antioxidant readouts. In non-volatile fraction, 1988 features were detected, of which 713 changed significantly, implicating remodelling of flavonoid- and catechin-centred pathways and purine metabolism. In volatile fraction, 1066 compounds were annotated, with 76 differing significantly; relative odor activity value based analysis indicated that unsaturated aldehydes and sulphur-containing compounds drive a roasted, full-bodied profile in black tea, whereas alcohols, esters and selected terpenoids confer fresher, fruity notes in green tea. Overall, these results support a processing-associated bitterness–aroma rebalancing pattern and nominate candidate chemical indicators for quality evaluation.