CONTRIBUTION OF VOLATILE THIOLS TO THE AROMA OF RIESLING WINES FROM THREE REGIONS IN GERMANY AND FRANCE (RHEINGAU, MOSEL, AND ALSACE)

The vocabulary used to describe wine aroma is commonly organized according to color, raising the question of whether they reflect the reality of olfactory perception. Previous studies have assumed this convention of color-aroma matching, and have investigated color’s influence on the perception of aroma only in dyed white wine or in red wine from particular places of origin. Here 48 white and red varietal wines from around the world were evaluated in black glasses then in clear glasses by a panel of wine experts, who gave intensity ratings for aroma attributes commonly used by wine professionals. In black glasses, aromas conventionally associated with white wine were perceived in the red wines, and vice versa.

Right after the pouring of wine in a glass, a myriad of volatile organic compounds, including ethanol, overwhelm the glass headspace, thus causing the so-called wine’s bouquet [1]. Otherwise, it is worth noting that during wine tasting, most people automatically swirl their glass to enhance the release of aromas in the glass headspace [1]. About a decade ago, Swiss researchers revealed the complex fluid mechanics underlying wine swirling [2]. However, despite mechanically repeated throughout wine tasting, the consequences of glass swirling on the chemical space found in the headspace of wine glasses are still barely known.

From the chemical angle, Champagne wines are complex hydro-alcoholic mixtures supersaturated with dissolved carbon dioxide (CO₂). During the pouring process and throughout the several minutes of tasting, the headspace of a champagne glass is progressively invaded by many chemical species, including gas-phase CO₂ in large majority. CO₂ bubbles nucleated in the glass and collapsing at the champagne surface act indeed as a continuous paternoster lift for aromas throughout champagne or sparkling wine tasting [1]. Nevertheless, inhaling a gas space with a concentration of gaseous CO₂ close to 30% and higher triggers a very unpleasant tingling sensation, the so-called “carbonic bite”, which might completely perturb the perception of the wine’s bouquet.

Xinomavro is a red grape variety from Northern Greece (Protected Designation of Origin), known for the nice acidities, perfectly appropriate for sparkling wine production (Rosé and Blanc de Noir). The elabo- ration of sparkling wine requires technical as well as scientific skills. Although the impact of the yeast strains and their metabolites on the final product quality is well documented, the action of bacteria still remains unknown.
The present work focuses (i) on the population diversity of lactic acid bacteria isolated from sparkling wines and (ii) on the technological effect of the species during sparkling wine elaboration.

During wine aging many compositional changes take place. In particular, aroma undergoes dramatic modifications through a wide range of reactions that to date are only partly understood. Italy owns one of the largest ampelographic heritages worldwide, with over three-hundred different varieties. Among these, many white grapes are employed for the production of dry still white wines. Some of these wines are consumed young while others are more prone to aging. For many of these wines, the aging patterns related to volatile composition are still unknown.