## 3 Results
### Extraction of Aromatic Compounds versus Type of Closure  
Two extraction methods (HP-SPME and TD) were used to obtain volatile compounds of sparkling wine after second fermentation and aging for 94 months. The obtained chromatograms of bottle-aged sparkling wine closured with closure A and isolated by TD and HP-SPME are shown in Figure 2. A summary of the data obtained by both extraction methodologies is presented in Table A1 (Appendix A). Briefly, the number of identified compounds extracted from TD (65) was slightly higher than HP-SPME (53). Figure 2: Chromatograms of sparkling wine bottle aging closured with cork stoppers (closure A) isolated by TD and HP-SPME. These results show that both methodologies are appropriate for the analysis of volatile compounds in sparkling wine. SPME and TD have been successfully used for the identification of aromatic compounds in wine [25; 26; 36; 40; 53; 54; 55; 56] and sparkling wine [23; 24; 57]. Therefore, TD required 30 mL of sample for extraction, while HP-SPME used 10 mL. Furthermore, TD is a time-consuming process (2 h) and requires temperature for extracting volatile compounds. Both depended on the equilibrium partitioning of the volatile compounds between the solution (or sparkling wine) and gas phase. Then, the solutes were extracted from a liquid phase of an aqueous matrix or wine and migrated into a polymer phase; they fit inside the needle of a syringe-like device in the case of HP-SPME and filled a desorption tube in the case of TD. Then, in the case of TD, a thermal desorption-step process followed by a preconcentration step (TD) was performed using a cryotrap. The most important disadvantage of HP-SPME is the lack of sensitivity [41]. In this study, TD extraction was designed with the aim of benefiting from the higher amount of sorbent, as well as the trap focusing, for the purpose of increasing the sensitivity. The extracted compounds are classified into families, according to their chemical nature, as acids, alcohols, alkanes, esters, ethers, ketones and others. Figure 3 shows the percentages of sparkling wine families of volatile compounds extracted by HP-SPME and TD, considering all analyzed closures. As can be seen, some differences were observed in terms of the percentages of the major families of volatiles. HP-SPME allowed for the more effective extraction of esters, considering both the percentage of area (66.1%) and the number of compounds (19). Furthermore, HP-SPME showed a higher proportion of ketones (1.8%) and others (26.2%). On the contrary, the proportion of alcohols (40.6%), ethers (17.0%), alkanes (2.6%), terpen (3.0%) and acids (4.0%) was higher in TD extracts than HP-SPME (1.9%, 2.0%, 0.9%, 0.1% and 0.8%, respectively). The most important group of compounds for sparkling wine aroma are ethyl esters of aliphatic acids [23]. Although HP-SPME allowed for the extraction of a greater number of esters, TD and HP-SPME were appropriate methods for extracting common esters such as methyl 2,4-dimethylhexanoate, ethyl octanoate, ethyl decanoate, ethyl anradidate or ethyl hexanoate in the sparkling wine samples (Table 1, Appendix A). Other ester compounds extracted using HP-SPME and TD were ethyl 9-decenoate, diethyl succinate and ethyl butyrate. All these compounds have already been identified in sparkling wines [23; 25; 58; 59; 60]. Diethyl succinate is a post-fermentation volatile formed during the aging of sparkling wines in contact with lees after second fermentation [23]. For this reason, this compound is  
Figure 3: Percentages of sparkling wine families of volatile compounds and number of compounds extracted by HP-SPME and TD methods. Compounds are aggregated in eight families. a signal of the evolution of sparkling wines during aging [24; 25]. Overall, representative esters were detected by both extraction methodologies, but HP-SPME was the quickest and most straightforward method for extracting them.