Hydroxycinnamate esters of vitis vinifera: changes during white vinification, and effects of exogenous enzymic hydrolysis

The composition of total hydroxycinnamates, as determined by high‐performance liquid chromatography (h.p.l.c), changes progressively during vinification, with little alteration in the ultraviolet spectrum. Enzymic activity during crushing and juice preparation leads to variable concentration of a glutathione derivative of the major component, caffeoyl tartaric acid. After fermentation begins, there is then partial hydrolysis of tartaric acid esters to free hydroxycinnamic acids, and formation of ethyl esters. Ten hydroxycinnamate and hydroxycinnamic acid components, all having tram‐configuration, were identified in a young Riesling wine. The course of phenolic change during commercial vinification of Chardonnay grapes was also examined. All components were quantitated as mg litre−1 ‘caffeic acid equivalents’ (CAE). Spectral estimates at 320 nm of total hydroxycinnamates as mg litre−1 CAE were 10‐15% higher than integrated h.p.l.c. measures of individual components. Six months after vintage, total hydroxycinnamates were 80% of amounts originally present. Use of a specific enzyme, hydroxycinnamic acid ester hydrolase, gives rapid alteration of phenolic composition in white wines. Sensory assessment of the effect of such treatment is reported for treatment of the Chardonnay wine.