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.