Metabolomics and sensomics reveal non-volatile flavor dynamics in summer–autumn steamed green tea flakes processing

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Summer-autumn steamed green tea flakes have attracted attention as a cost-effective extended product of traditional spring shaded Tencha, but their metabolic and sensory transformations during processing remain unexplored. This study employed non-targeted metabolomics and sensomics approaches, including quantitative descriptive analysis, electronic tongue evaluation, and weighted gene co-expression network analysis-to systematically investigate the dynamic non-volatile metabolic transformations and their associations with sensory attributes. A total of 228 metabolites were significantly correlated with sensory traits. Results showed a decline in green characteristics, while seaweed-like notes, umami intensity, and overall preference were enhanced, particularly during the second oven-drying stage. Flavonoid glycosides underwent selective degradation under moist-heat conditions, and the concurrent decrease in tea polyphenols-particularly EGCG-collectively contributed to the reduction in astringency, while the accumulation of trehalose, arachidonic acid, eicosapentaenoic acid, and 17α,20α-dihydroxypregn-4-en-3-one potentially enhanced flavor balance and seaweed-like characteristics. These findings provide a biochemical basis for optimizing Tencha production using summer-autumn tea materials.