Inhibition Mechanism of Glucosylated Steviol Glycosides on Volatile Bitter Substances in Alcoholic Beverages

To elucidate the effect of glucosylated steviol glycosides (GSG) on volatile-associated bitterness in alcoholic beverages and its molecular mechanisms, a formulated alcoholic beverage model system was employed to investigate the influence of GSG on the volatilization behavior, sensory perception, and receptor binding of volatile bitter compounds. Headspace solid-phase microextraction gas chromatography-olfactometry-mass spectrometer was used to determine the odor activity values of volatile compounds, to identify key aroma-active constituents, and to evaluate the impact of GSG addition on volatile release in alcoholic beverages. Molecular docking combined with sensory evaluation was applied to identify volatile bitter compounds in alcoholic beverages and to characterize their binding interactions with the human bitter taste receptor TAS2R14. Furthermore, sensory analysis was conducted to verify the inhibitory effect of GSG on the bitterness elicited by volatile compounds. Molecular dynamics simulations were performed using the TAS2R14 receptor protein in complex with the identified major volatile bitter compounds and the principal component of GSG, rebaudioside A, to elucidate the inhibitory mechanism of GSG at the receptor level. The result showed that 40 volatile compounds were detected in the model alcoholic beverage. The headspace concentrations of all compounds, except lauric acid, were significantly reduced following GSG addition. Based on GC-O analysis and calculated binding energies with TAS2R14, 7 volatile compounds were identified as the primary volatile contributors to bitterness in alcoholic beverages, including ethyl caprylate, ethyl palmitate, benzyl alcohol, isoamyl alcohol, octanoic acid, furfural, and benzaldehyde. Sensory evaluation demonstrated that GSG significantly reduced the perceived bitterness intensity of these 7 compounds, and a more pronounced inhibitory effect was observed for bitter esters. Molecular simulation results revealed that rebaudioside A could form a stable complex with TAS2R14 and competitively inhibit the binding of bitter compounds to the receptor through a more favorable binding free energy profile and increased hydrogen-bond interactions. These findings indicated that GSG suppressed bitterness in alcoholic beverages by reducing the release of volatile bitter compounds and by competitively blocking their binding to bitter taste receptors. This study provided a theoretical basis for the optimization of flavor quality in alcoholic beverages.