## 3 Results
### Effect of the Type of Closure through Compositional Data Analysis  
Based on the results obtained, the type of closure used during the second fermentation can influence the aroma composition of the resulting sparkling wine. This impact may result from the desorption of volatile compounds from the closures into the wine [8; 18] or be related to the level of oxidation. In the case of still wine, ref. [72] described that wines sealed with different types of closures for four years differed significantly in their content of some volatile chemicals, such as 1-butanol, 2-phenylethanol, 2-nonanol and ethyl decanoate. Additionally, ref. [73] discovered that eight volatile compounds (isoamyl acetate, ethyl decanoate, nonanoic acid, n-decanoic acid, undecanoic acid, 2-furancarboxylic acid, dodecanoic acid, and phenylacetaldehyde) placed a role in differentiating wine closures and were linked to the oxidation level of Cabernet Sauvignon wines. The impact of six different closures used in bottle aging after second fermentation on the volatile composition of sparkling wine has been evaluated using the compositional analysis of a data matrix that included the compounds extracted by HP-SPME. First, two groups were analyzed: cork stoppers (cork 1 and cork 2) and screw-cap closures (from CC1 to CC4). We used a compositional data set with n = 37 stoppers (n = 13 group cork and n = 24 group screw cap) and D = 57 volatile compounds. Due to the substantial number of zeros, we first selected the volatile compounds detected in more than five stoppers--that is, with a percentage of zeros below 80%. This reduced the number of parts of our composition to D = 16, and their names are listed in Table 3. Additionally, the corresponding percentage of replaced zeros and the notation used in the figures to avoid the lengthy names of certain compounds are also provided. According to the nature of these zeros, the log-ratio EM imputation algorithm was applied [52]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Code** & **Volatile Compounds** & **\% Zeros Replaced** \\ \hline \(x_{1}\) & 1,1,5-Trimethyl-1,2-dihydronaphthalene & 75.7\% \\ \(x_{2}\) & 3-Alphydroisoquinoline,1-[3-hydroxybenzyl]-6-methoxy- & 62.2\% \\ \(x_{3}\) & 4-(2,3,6-Trimethylphenyl)-1,3-butadiene & 70.3\% \\ \(x_{4}\) & Carbon dioxide & 70.3\% \\ \(x_{5}\) & Diethyl succinate & 0.0\% \\ \(x_{6}\) & Dimethylamine & 70.3\% \\ \(x_{7}\) & Ethyl 9-decenoate & 13.5\% \\ \(x_{8}\) & Ethyl hexanoate & 0.0\% \\ \(x_{9}\) & Ethyl octanoate & 56.8\% \\ \(x_{10}\) & Ethyl trans-4-decenoate & 32.4\% \\ \(x_{11}\) & Isoamyl alcohol & 73.0\% \\ \(x_{12}\) & Lactamide & 51.4\% \\ \(x_{13}\) & Octanoic acid & 56.8\% \\ \(x_{14}\) & Oxirane, 2-(1,1-dimethylethyl)-3-ethyl-cis- & 46.0\% \\ \(x_{15}\) & Phenylethyl Alcohol & 2.7\% \\ \(x_{16}\) & alpha-Ionone & 21.6\% \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Oenological parameters of base wine before and after the addition of a “triage solution”. The values of the whole center and subgroups center (cork and screw-cap closures) are presented in Table 12 (Appendix A). Overall, the most abundant part is ethyl hexanoate \((x_{8})\), which is also observed in the screw-cap subgroup. However, in the cork subgroup, the most abundant part is ethyl ocanoate \((x_{9})\). Both are ester compounds--the most abundant family of compounds detected in sparkling wine samples (Figures 5 and 6). To better understand these results, a geometric-mean bar plot comparing the compositional center of the entire sample with the compositional center of cork stoppers and screw-cap subgroups is shown in Figure 5. The volatile compounds with a larger relative difference compared to the global center were dimethylamine \((x_{6})\) and ethyl ocanoate \((x_{9})\). It is clear from Figure 5 that the proportion amount of dimethylamine \((x_{6})\) was higher in screw-cap closures than cork stoppers relative to the entire sample. Dimethylamine primarily forms through the decarboxylation of amino acids at various stages of vinification.