Olfactory impact of dimethyl sulfide on red wine fruity esters aroma expression in model solution

摘要

Aim: The goal of this study was to evaluate the impact of dimethyl sulfide (DMS) on the fruity aroma of a complex mixture containing 12 red wine esters.Methods and results: Aromatic reconstitutions were prepared using pure commercial esters and acetates at the average concentrations found in red wines, as well as several concentrations of DMS. The olfactory thresholds of DMS in such matrices were: 1.74 μg/L in dilute alcohol solution, 2.80 μg/L in fruity aromatic reconstitution (12 esters) in dilute alcohol solution, and 3.67 μg/L in fruity aromatic reconstitution in dearomatized red wine. The "olfactory threshold" of the fruity pool, consisting of the 12 esters, was calculated in two different matrices: dilute alcohol solution and dilute alcohol solution supplemented with 5 μg/L DMS. The presence of DMS in the mixture led to significantly decreased of the "olfactory threshold" of the fruity pool, highlighting its effect in increasing overall aroma intensity. Sensory profiles were then evaluated to investigate the qualitative impact of DMS on fruity aroma perception.Conclusions: These results confirmed the sensory importance of DMS, suggesting that it was an active contributor to the black-berry fruit nuances in the fruity matrix studied. This compound participated, both quantitatively and qualitatively, in modulating black-berry fruit aroma and, more specifically, in enhancing blackcurrant aroma.Significance and impact of the study: Studies investigating fruity aromas in red wines over the past decade have discussed the implication of DMS in fruity aroma expression. Although DMS does not present fruity aromas, this study clearly shows its indirect impact on fruity aroma expression, via particular perceptive interactions, in fruity model mixture. IntroductionPrevious research on the fruity character of red wines highlighted the role of ethyl esters and acetates (Etiévant, 1991; Bertrand et al., 1995; Pineau et al., 2009; Falcao et al., 2012; Lytra et al., 2012a; Lytra et al., 2012b), produced by yeast metabolism during alcoholic fermentation, a phase where red- and black-berry fruit aromas are formed (Pineau et al., 2011). The literature provides evidence that, besides these esters, other compounds that do not necessarily present fruity aromas may have an important impact on the overall fruity aroma of wine. For example, furaneol and homofuraneol, with strong caramel aromas, seem to have an enhancing effect on the perception of red-berry fruit aroma (Kotseridis and Baumes, 2000). In addition, some thiols (3-sulfanylhexan-1-ol) (Bouchilloux et al., 1998) and other volatile sulfur compounds (dimethyl sulfide) may also affect the perception of fruity aroma in red wines (Anocibar-Beloqui et al., 1996; Segurel et al., 2004; Escudero et al., 2007). Some C13-norisoprenoids, such as β-damascenone, are also generally considered to affect red wine fruity aroma (Escudero et al., 2007; Pineau et al., 2007). Finally, in complex mixture, the direct role of diacetyl in fruity expression has recently been highlighted, as well as the indirect roles of acetoin, acetic acid, and γ-butyrolactone (Lytra et al., 2012b).Dimethyl sulfide (DMS), a light sulfur compound, has been described in a wide range of food products: cooked meat (Jensen et al., 2002) and cheese (Carbonell et al., 2002) as well as tomatoes (Buttery et al., 1971), citrus (Shaw et al., 1980), melons (Homatidou et al., 1992), truffles (Diaz et al., 2003), cereals (Ren, 2001), and some vegetables (Ulrich et al., 2001; Tulio et al., 2002). Its presence in beer and wine has also been reported (Loubser and Du Plessis, 1976).The olfactory threshold of DMS was established at 27 μg/L in red wine (Anocibar-Beloqui et al., 1996) but seems to be strongly dependant on the matrix and tasting panel, as it has also been estimated at 30 to 45 μg/L (Meilgaard, 1982) and 22 to 60 μg/L (Etiévant, 1991). At the end of alcoholic fermentation, it is present at relatively low levels - generally well below its olfactory threshold - but may reach high concentrations in certain wines during bottle aging, up to mg/L levels (Marais, 1979; de Mora et al., 1993; Anocibar-Beloqui, 1998; Loscos et al., 2008). For example, the study of 17 commercial wines, aged from 1 to 21 years old, showed DMS levels ranging from 3 μg/L in younger wines to 711 μg/L in older vintages (Dagan, 2006).Anocibar-Beloqui et al. (1996) reported that the addition of DMS at concentrations above its olfactory threshold conferred blackcurrant and raspberry notes to some young wines. These observations were confirmed in Grenache and Syrah wines by Segurel et al. (2004). Escudero et al. (2007) suggested that DMS played the role of fruity flavor enhancer by observing that, while 10 μg/L of this compound was not directly perceived in dearomatized wine, it conferred "sweet-fruity" or "green olive" notes to more complex mixtures.In older wines, especially those aged in oak barrels, the addition of DMS may produce truffle or hay