Identification of the causes of aroma differences in white tea under different withering methods by targeted metabolomics

Sunlight withering (SWT) enhanced the floral aroma of white tea, whereas withering–tank withering (WWT) enriched its grassy aroma. This study investigated the impact of diverse withering methods on white tea aroma, examining aroma formation mechanisms by analyzing changes in essential compounds, their precursors, and enzyme activities during these treatments. Findings revealed that tea at 50% moisture concentration decreased the concentration of isopentenyl pyrophosphate and dimethylallyl pyrophosphate, leading to increased levels of linalool, geraniol, and β-myrcene. Sunlight spurred non-enzymatic reactions, elevating β-ionone concentration. The breakdown of linoleic and linolenic acids increased the hexanal and (Z)-3-hexenol levels. Enzyme activity analysis indicated that the prominent floral aroma in SWT was linked to heightened geranyl pyrophosphate synthase and alcohol dehydrogenase activity, enriching terpene–catalyzed products and benzeneacetaldehyde concentration, respectively. Elevated levels of lipoxygenase and arogenate dehydratase promoted grassy compounds in WWT. This study underscores how withering methods shape white tea aromas and offers operational insights.