Effect of glass swirling on the removal of ‘reductive’ off-odours caused by H2S in wine

‘Reductive’ off-odours, particularly those associated with hydrogen sulfide (H2S), can greatly affect the sensory quality of wine by masking desirable fruity aromas. This study investigated the effect of glass swirling on the volatilisation of free H2S and its subsequent influence on aroma perception in model and Chenin blanc wine. Sensory analysis and chemical measurements were conducted to evaluate the changes in ‘reductive’ off-odours and ‘fruity’ attributes following glass swirling and the exposure of wine to ambient air conditions after swirling. H2S analyses, conducted under ambient and in an anaerobic environment, revealed that a decrease in H2S concentrations after swirling was mainly due to volatilisation and not oxidation. Varietal thiol concentrations, however, were not significantly influenced by these treatments. High H2S concentrations were closely associated with increased ‘reductive’ off-odours and diminished ‘fruity’ characteristics. Swirling for 30 seconds significantly decreased the perception of ‘reductive’ aromas while enhancing ‘fruity’ attributes such as ‘pineapple’, ‘passionfruit’, and ‘peach/apricot’. Overall, leaving the glass open post-swirling did further improve the aroma perception of the fruity characters; however, this effect was strongly influenced by the concentration of H2S and the wine matrix.