WHICH IMPACT FOR PROANTHOCYANIDIC TANNINS ON RED WINE FRUITY AROMA? SENSORY AND PHYSICOCHEMICAL APPROACHES

Abstract

Previous research on the fruity character of red wines highlighted the role of esters. Literature provi- des evidence that, besides these esters, other compounds that are not necessarily volatiles may have an important impact on the overall aroma of wine, contributing to a modulation of its global aromatic expression. The goal of this work was to assess the olfactory consequences of a mixture between esters and proanthocyanidic tannins, through sensory and physico-chemical approaches.

Sensory analysis of numerous aromatic reconstitutions, including triangular tests, detection thresholds, and sensory profiles, were conducted in order to evaluate the sensory impact of tannins on red wine esters perception. Then, the impact of these non-volatile molecules on esters volatility, and thus taster stimulation, was evaluated thanks to the determination of partition coefficients.

Our results showed that the presence of tannins in the matrix significantly attenuated perception of fruity notes. In a consistant way, physico-chemical analysis demonstrated also that the presence of proanthocyanidic tannins in dilute alcohol solution resulted in a decrease in ester partition coefficients and thus in a decrease in ester contents in the headspace. This fact highlighted pre-sensory changes. Finally, a new sensory tool was developed, consisting in an ISO glass containing two identical compartments separated by a vertical glass wall, providing a way to compare perceived odours according to whether or not the components of the odour mixtures were actually mixed in solution. This new tool was used to demonstrate the impact of the physical mixture of proanthocyanidic tannins and esters in order to demonstrate the exclusive involvement of pre-sensory interactions.

These results confirmed the sensory impact of some non-volatile compounds on odor perception. Finally, esters partition coefficient evaluation revealed a decrease of the volatility of esters when tannins were present in the matrix, thus corroborating sensory evaluation results. Proanthocyanidic tannins decrease esters volatility when they are added in the matrix, thus reducing orthonasal taster stimulation and consequently reducing red wine fruity notes perception. Such a study should be extended to anthocyanins and other oenological tannins and, including their concentration ranges, to assess the impact of the phenolic matrix on red wines aroma perception.