Insights into the mechanism of different withering methods on flavor formation of black tea based on UPLC-MS/MS, GC-MS and OAV analyses

This study evaluated the effects of red-light withering, shaking withering, and their combined withering (RS) on the physicochemical properties and flavor quality of summer–autumn black tea. The results showed that all withering treatments reduced the tea polyphenol content, while RS exhibited the highest contents of amino acids (2.04%) and soluble sugars (3.51%). UPLC–MS/MS analysis identified a total of 334 differential metabolites compared with conventional indoor static withering, and RS mainly affected metabolic pathways related to amino acids, carotenoids, and lipids. GC–MS and odor activity value (OAV) analyses revealed that trans-β-ionone (263.51), phenethyl alcohol (7.24), phenylacetaldehyde (16.41), and related compounds were more prominent under RS , thereby enhancing and enriching the floral and fruity aroma characteristics of black tea. Overall, RS synergistically improved taste composition and enhanced floral and fruity aroma expression during withering, which provides theoretical support for high-aroma processing of summer-autumn black tea. • All three withering treatments promoted linoleic acid metabolism • Metabolic shifts drive aroma-active compound accumulation • Combining red light and shaking can improve the flavour quality of black tea • trans-β-Ionone, Linalool, phenylacetaldehyde are the main contributors to the aroma.