# Impact of Cork Closures on the Volatile Profile of Sparkling Wines during Bottle Aging
## 4 Discussion  
Ethyl esters are the main class of aroma compounds released by the autolysis of yeasts in sparkling wines produced by the traditional method and they contribute to the fruity and floral-like aromas of these wines [16]. In our study, the levels of several ethyl esters were significantly higher in both sparkling wines sealed with 2D corks. The preservation of ethyl esters during bottle storage has been a challenge for winemakers as ethyl esters tend to hydrolyze over time due mostly to the low pH of wines [17]. Hence, a stopper able to preserve better the ethyl ester composition of sparkling wines can improve their shelf life and the sensory attributes expected by consumers. Notably, most ethyl esters present in both sparkling wines (Tables 1, 2, S1 and S2)--with exception of ethyl decanoate, hexyl acetate, and phenylethyl acetate--showed a significant increase over time. Despite the behavior of these compounds has been studied during the aging period in contact with lees [7; 8], the information about their evolution trends after disgorging is limited [18].  
\begin{table}
\begin{tabular}{l c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**ClassCompound**} & \multicolumn{3}{c}{**21 Models 1**} & \multicolumn{3}{c}{**21 Models 1**} & \multicolumn{3}{c}{**21 Models 1**} & \multicolumn{3}{c}{**21 Models 2**} & \multicolumn{3}{c}{**21 Models 3**} & \multicolumn{3}{c}{**22 Models 4**} & \multicolumn{3}{c}{**22 Models 5**} & \multicolumn{1}{c}{**23 Models 6**} \\  & \multicolumn{1}{c}{2D} & MA & \(p\) & 2D & MA & \(p\) & 2D & MA & \(p\) & **Menthal 7** & **2** & **Threshold 3** \\ \hline \hline \multirow{2}{*}{
\begin{tabular}{} \end{tabular} } & \multirow{2}{*}{\(1.46\pm 0.38\)} & \multirow{2}{*}{\(1.30\pm 0.48\)} & \multirow{2}{*}{\(1.30\pm 0.48\)} & \multirow{2}{*}{\(m\)} & \multirow{2}{*}{\(0.97\pm 0.14\)} & \multirow{2}{*}{\(0.27\pm 0.23\)} & \multirow{2}{*}{\(m\)} & \multirow{2}{*}{\(4.52\pm 0.65\)} & \multirow{2}{*}{\(2.43\pm 0.45\)} & \multirow{2}{*}{*} & \multirow{2}{*}{\(\bullet\)} & \multirow{2}{*}{\(\bullet\)} \\  & & &  
Camphor has been previously identified by our group as only present in wines sealed with natural cork [19], which agrees with the results observed for both sparkling wines sealed with 2D stoppers. The most probable hypothesis is the desorption of camphor from natural cork to wines, which is also corroborated by the detection of this compound in wine model solution extracts of natural cork granules [20]. Based on these facts, camphor seems to be a good marker to discriminate wines bottled with natural cork discs versus other closures.  
The levels of two alcohols (3-hexen-1-ol and 1-hexanol), one ketone (2-undecanone) and one isoprenoid (\(\beta\)-damascenone) were also significantly influenced by the type of closure in sparkling wine #1. Alcohols can be substrates for wine oxidation originating their correspondent aldehydes [21]. Thus, the lower levels of 3-hexen-1-ol and 1-hexanol in sparkling wine #1 sealed with MA stoppers may be due to their oxidation in hexanal and 3-hexenal, respectively. Though these aldehydes were not detected in the volatile composition of sparkling wine #1 under our experimental conditions. However, 2-undecanone, a ketone that may be also formed by oxidation [21], was found in higher levels in samples sealed with MA. Finally, \(\beta\)-damascenone is mainly produced from direct degradation of carotenoid molecules during fermentation [22]. Higher levels of this isoprenoid were previously found in a dry white wine sealed with natural cork compared with microagglomerated cork [23], in agreement with the results obtained for sparkling wine #1 at 24 months.