Characterization of key aroma compounds contributing to tropical fruity and Citrus notes and the mechanism of characteristic aroma formation in Dali-variety black tea

Dali-variety ( Camellia taliensis (W. W. Sm.) Melch.) black tea (DLBT) possesses distinctive tropical fruit and citrus aromas, yet its key aroma compounds and formation mechanism remain unclear. To address this, we employed a molecular sensory science approach. GC–MS identified 143 volatiles across 10 DLBT samples, from which 21 aroma-active compounds were screened via GC-O/AEDA. OAV calculations further pinpointed 9 key aroma compounds. Reconstitution and omission experiments definitively identified octanal as the primary source of the tropical fruit note, while linalool, nonanal, and decanal were crucial for the sweet citrus character. Dynamic profiling of volatiles, enzyme activities and gene expression during processing identified withering and drying as key stages for DLBT's unique aroma. Water stress during withering rapidly upregulates the activities of fatty acid metabolic enzymes and the expression levels of related genes, promoting the accumulation of key aroma precursors and laying the material foundation for the final aroma.