Effect of hydroxycinnamic acids on ester-improving and aroma-enhancing of Cabernet Sauvignon red wine and its mechanism.

The effect of hydroxycinnamic acids on the aroma formation of Cabernet Sauvignon dry red wine and the molecular mechanism were explored. Four hydroxycinnamic acids were added singly before alcoholic fermentation. Volatile components were analyzed qualitatively and quantitatively and aroma characteristics were evaluated by sensory analysis. The thermodynamic parameters of caffeic acid interacted to five esters were determined in simulated solution, and the effect of caffeic acid on the volatility of the esters was explored with GC-FID. Dispersion-corrected density functional theory (DFT) was applied for the molecular mechanism investigation between caffeic acid and esters. The results showed that the addition of hydroxycinnamic acid to wine caused an increase of esters, particularly in acetate, with ranging from 3.01 to 43.03 mg/L. Sensory evaluation revealed maximum intensity increases of 79.4 % (floral aroma), 26.3 % (fruity aroma), and 21.1 % (sweet aroma) in the treatment group. The interaction between caffeic acid and esters is a spontaneous exothermic reaction that inhibited the volatilization of esters. The retention effect is affected by the concentration of caffeic acid and the skeletal structure of esters. Theoretical studies have shown that the interaction between caffeic acid and esters is mainly driven by a combination of hydrophobic interactions, hydrogen bonding and dispersion, with the main driving force varying depending on the ester backbone. The hydroxyl group of caffeic acid and the ester group on the esters are the key sites for molecular interactions.