Zongjie Wu

Roasting shapes the sensory quality of Wuyi Rougui tea, but the links between sensory changes and flavor compound remodeling across roasting stages remain insufficiently characterized. Sensory evaluation and electronic sensory analysis showed that RG2O exhibited enhanced sensory characteristics, including fruity-floral and cinnamon-like aroma attributes. GC-MS analysis identified 362 volatile metabolites, with esters, terpenoids, and heterocyclic compounds as the major classes. OAV and VIP analyses suggested that 1-nonen-3-one, pyrazines, and other differential volatiles may contribute to the variation of mineral and roasted aroma characteristics. Non-volatile analysis showed that gallic acid (GA), gallocatechin gallate (GCG), and theabrownins were associated with taste-related attributes, including thickness, while roasting was accompanied by the conversion of protopectin into soluble pectin. Molecular docking provided predictive evidence for potential interactions between GA/GCG and the calcium-sensing receptor related to kokumi-associated perception. Overall, roasting was associated with coordinated remodeling of volatile and non-volatile metabolites, together with changes in pectin components, contributing to the reconstruction of flavor characteristics in Wuyi Rougui tea.

As important factors to oolong tea quality, the accumulation and dynamic change in aroma substances attracts great attention. The volatile composition of oolong tea is closely related to the precursor contents. Fatty acids (FAs) and their derivatives are basic components of oolong tea fragrance during the postharvest process. However, information about the precursors of FAs during the postharvest process of oolong tea production is rare. To investigate the transformation of fatty acids during the process of oolong tea production, gas chromatograph–flame ionization detection (GC-FID) was conducted to analyze the composition of FAs. The results show that the content of total polyunsaturated FAs initially increased and then decreased. Specifically, the contents of α-linolenic acid, linoleic acid and other representative substances decreased after the turn-over process of oolong tea production. The results of partial least squares discrimination analysis (PLS-DA) showed that five types of FAs were obviously impacted by the processing methods of oolong tea (VIP > 1.0). LOX (Lipoxygenase, EC 1.13.11.12) is considered one of the key rate-limiting enzymes of long-chain unsaturated FAs in the LOX-HPL (hydroperoxide lyase) pathway, and the mechanical wounding occurring during the postharvest process of oolong tea production greatly elevated the activity of LOX.