Chapter 13
Downloaded by MONASH UNIV on November 25, 2015 | http://pubs.acs.org Publication Date (Web): November 24, 2015 | doi: 10.1021/bk-2015-1203.ch013
Critical Oxygen Levels Affecting Wine Aroma: Relevant Sensory Attributes, Related Aroma Compounds, and Possible Mechanisms Maurizio Ugliano,* Stéphanie Bégrand, Jean-Baptiste Diéval, and Stéphane Vidal Nomacorc France, Av. Yves Cazeaux, Rodilhan 30230, France *E-mail:
[email protected].
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 (rosé), 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 rosé 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 ß-damascenone increased with higher oxygen exposure, while fruity thiols such as 3-sulfanylhexanol (3SH) decreased. H2S and methyl mercaptan were mostly implicated
© 2015 American Chemical Society In Advances in Wine Research; Ebeler, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.
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.
Downloaded by MONASH UNIV on November 25, 2015 | http://pubs.acs.org Publication Date (Web): November 24, 2015 | doi: 10.1021/bk-2015-1203.ch013
Introduction In recent years, a number of different studies have shown that the type of closure, in particular its ability to allow a certain degree of oxygen exposure in the bottle, plays a crucial role in the chemical and sensory evolution of the wine during bottle maturation (reviewed in (1)). Overall, the conclusions of these studies support the anecdotal observation that, in order for bottle aging to contribute positively to wine quality, a certain degree of oxygen exposure is required. Nevertheless, several aspects remain to be clarified. First, in view of the great variety of wine styles produced in different parts of the world, the type of aroma attributes that can be effectively modulated by oxygen needs to be better characterized. This appears crucial in order to provide practical information as to which wine styles can be more effectively modulated by informed closure selection. Second, while extreme oxygen exposure levels (e.g. too little or too much) during bottle maturation can result in oxidative off-odors such as reduction or oxidation, the outcomes of intermediate oxygen levels, which are most common in today industry, are not well described. Among these, some studies indicate that the fruity attributes of wine can be affected by closure-derived oxygen, but the trends observed seem to be inconsistent. In fact, while some authors indicated increased fruit expression at lower oxygen, other data show the opposite (2–4). In addition, the chemical compounds and transformations implicated in the sensory changes associated with the mild levels of oxygen exposure found during bottle maturation need to be clarified. In this study, the sensory changes associated with bottle maturation under closures allowing different oxygen exposure levels have been studied for 126 wines. The purpose was to evaluate which aroma attributes were more frequently associated with changes in oxygen exposure, as well as to characterize the oxygen levels at which these changes might occur. The mechanisms underlying oxygen interactions with different wine aroma compounds potentially implicated in these changes are also discussed.
Materials and Methods Wines were collected in the period 2011-2014 from different commercial and experimental cellars located in various European winemaking regions. Preliminary assessments were carried out to ensure adequate bottling conditions at each cellar. Thirty-six wine types from different grape varieties were bottled, using at least two different Nomacorc Select series closures allowing defined oxygen ingress values (Table 1). Oxygen ingres values of individual closure types were measured as described by Dieval et al. (5). At the moment of tasting, the wines were in an age bracket of 9-19 months (whites), 5-11 months (rosé), 12-48 206 In Advances in Wine Research; Ebeler, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.
months (reds). Within single wines, the difference in oxygen exposure created by the different closures was in the range of 0.5-1.2 mg (whites), 0.4-1.2 mg (rosé), and 0.6-1.4 mg (reds). A total of 126 wines were submitted to sensory analysis, including 28 white wines, 47 rose’ wines and 51 red wines.
Downloaded by MONASH UNIV on November 25, 2015 | http://pubs.acs.org Publication Date (Web): November 24, 2015 | doi: 10.1021/bk-2015-1203.ch013
Table 1. Oxygeningress (mg of O2) of the Different Closures Used in the Study at Different Times of Bottle Aging
Sensory analysis was carried out at In Senso Veritas (Beaune, France), by a panel of 16 trained panelists. Evaluations were performed under white light, at room temperature, at isolated tables. The wines were evaluated on pre-defined attributes (11 for white wines, 12 for rose wines and 10 for red wines), rating each attribute on a 7 points continuous scale (from 0 to 6). Reference standards were provided for each one of the aroma attributes tested as indicated in Table 2. Wines were served in blind, with a random 3 digit code. Each panelist had a randomized order of presentation in order to avoid effects of order. Panelist performance was assessed using FIZZ software. For the sensory analysis data, analysis of variance (ANOVA) was carried out to assess the effect of oxygen exposure on individual aroma descriptors. Within each wine type, the number of times a single descriptor showed significant differences at p
