Varietal Thiols and Oxidative Instability: Variable Vulnerability and Sensory Impact
Prof. Maurizio Ugliano, from the University of Verona, analyzes the organoleptic consequences of oxidation in white and rosé wines, examining the sequence of chemical reactions leading to the loss of varietal aromatic compounds, with particular focus on polyfunctional thiols.
This video is an excerpt from the masterclass on wine instability organized by Vinidea. You can access the full recordings at this link: https://vinidea.it/en/product/wine-instabilities/
Technical Contents:
The presentation describes the sequence of oxidative reactions: ortho-diphenols transform into oxygenated quinones, strong electrophiles that immediately react with sulfur dioxide releasing acetaldehyde. This phenomenon, observable within the first hours, is modulated by the concentration of aldehyde-bound sulfur dioxide present in the wine.
Loss of Varietal Thiols:
Analysis of the reaction between oxygenated quinones and varietal volatile thiols: 3-mercaptohexanol (passion fruit, grapefruit), 3-mercaptohexyl acetate and 4-mercapto-4-methylpentan-2-one (boxwood, cat’s urine notes). Progressive attenuation leading to potential disappearance of varietal character in wines overexposed to oxygen.
Varietal Complexity:
Differentiation between wines with high thiol presence (Sauvignon Blanc) and wines with polyfunctional thiols present at concentrations near perception thresholds. In the latter, even small thiol losses can cause a drop below the perceptual threshold with significant organoleptic impact.
Temporal Progression:
Comparison between rapid reactions (hours-days: acetaldehyde release) and slower but organoleptically more impactful reactions (weeks-months: appearance of typical oxidative notes). Importance of preventive interventions in the early stages of oxidation.
This video is an excerpt from the masterclass on wine instability organized by Vinidea. You can access the full recordings at this link: https://vinidea.it/en/product/wine-instabilities/
