Critical Oxygen Levels Affecting Wine Aroma: Relevant Sensory Attributes, Related Aroma Compounds, and Possible Mechanisms

The importance of post-bottling oxygen to wine aroma development has been demonstrated. However, from a practical point of view, the degrees of oxygen exposures needed to induce significant aroma modification remain to be established. In addition, certain styles of wine are more responsive to oxygen than others, possibly reflecting the key role of specific aroma compounds with lower/higher oxygen sensitivity in their sensory profile. In this study, 36 wines from different grape varieties were submitted to sensory descriptive analyses. The wines were in an age bracket of 9-19 months (whites), 5-11 months (ros), 12-48 months (reds). Each wine had received at least two different oxygen exposure levels by means of different closures, with some wines tasted at different time points. In total, 96 wines were tasted. When considering only the contribution of closure-derived oxygen, aroma intensity, fruity attributes, and reduction were in white wines the sensory descriptors mostly affected by oxygen. In the case of ros wines, oxygen appeared to influence mainly aroma intensity and red fruit attributes, whereas for red wines red fruits, cooked fruits, spices and gamey were mostly affected. Analyses conducted on selected wines indicated that esters, largely associated with wine fruity aromas were not affected by oxygen. Conversely, the fruit-enhancer 13-damascenone increased with higher oxygen exposure, while fruity thiols such as 3-sulfanylhexanol (3SH) decreased. H2S and methyl mercaptan were mostly implicated with reduction attribute, and they might negatively affect expression of fruity attributes. The possible mechanisms implicated in the response of these compounds to oxygen are discussed.