Metabolomic and flavoromic insights into the effects of Polygonatum kingianum extract during black tea processing

This study aims to elucidate the effects of the compounding treatment of Polygonatum kingianum extract (PKE) on the sensory quality, flavor chemical characteristics, and potential functional activities of control Dianhong black tea (CK). The results showed that Polygonatum kingianum black tea (PKB) had a darker and more lustrous appearance, a sweeter and more mellow taste, and a distinct floral and fruity aroma along with a refreshing herbal fragrance. The water extract and soluble sugar contents of PKB increased from 41.20 to 44.98% and from 7.03 to 10.91%, respectively (p < 0.01). LC-MS analysis identified the downregulation of bitter-associated flavonol glycosides, including quercetin 3-glucosyl-(1 → 2)-galactoside and quercetin 3-galactoside, together with the upregulation of sweet-related metabolites such as mannose, sorbose, and 6-phosphogluconic acid. Comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-TOF-MS) analysis indicated that the volatile components of PKB, such as alcohols, ketones, and esters, significantly increased. The key aroma compounds cooperatively enhanced the aroma richness. Based on variable importance in projection (VIP) and Relative Odor Activity Value (ROAV) screening, 7 key aroma components were identified; among them, 2-methylbutanal (ROAV = 100) was the core component for fruity and sweet scents. These changes were associated with alterations in flavonoid, amino acid, carbohydrate, and aroma-related metabolic pathways. Overall, PKE treatment significantly improved the sensory quality and flavor characteristics of Dianhong black tea.