# Pairing Red Wine and Closure: New Achievements from Short-to-Medium Storage Time Assays
## 3 Results and Discussion
### Volatile Profile of Wines Sealed with Different Types of Closures
#### 3.4.1 Douro Red Wine
Based on its aroma descriptor [54], this result may help explain the aroma of cooked potatoes, which is empirically associated with micro-agglomerated cork stoppers. On the other hand, although it may be indicative of oxidation processes, its content depends on a complex network of factors; namely, its accumulation is modulated by interactions with other components of the wine [55; 56]. Three norisoprenoid derivatives were identified in both wines: safranal, \(\beta\)-damascenone, and 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN), which were present in higher concentrations (\(p<0.05\)) in the wine sealed with Natural Cork 1 compared to wine bottled with Micro A (Figure 5c). During bottle storage, oxidative degradation of carotenoids can lead to the production of norisoprenoids, and these compounds are released as a result of exposure to oxygen, which facilitates the breakdown of carotenoids, allowing for the formation of these key aroma markers [1; 57]. They may contribute to notes associated with saffron-like aromas (safranal) [58], petroleum and kerosene-like aromas (TDN) [22], and floral notes (\(\beta\)-damascenone), enhancing the fruity notes in wine [59]. Figure 4: Dendrogram and heatmap representation of Douro red wines sealed with Natural Cork 1 and Micro A stoppers: **(a)** the 196 volatile compounds identified in Supplementary Material Table S3, organized by chemical families separated by dashed lines; and **(b)** the combined information domains, including sensorial analysis, physicochemical parameters, phenolic compounds, and volatile organic compounds. Euclidean distances are included on the dendrogram \(Y\)-axis. A chromatic scale (from dark blue, minimum, to dark red, maximum) was used for each variable, normalized by autoscaling. We also noted the presence of a higher amount (\(p<0.05\)) of 1,3-dioxane and 2-methyl-1,3-dioxane in wine sealed with Natural Cork 1 (Figure 5d). Although these compounds are primarily formed during the fermentation process, their concentrations can increase significantly during aging, especially under oxidative conditions [39; 60]. The higher levels observed in the wine sealed with Natural Cork 1 may suggest that the stopper material could influence the oxidative environment within the bottle, promoting the formation or release of these compounds over time [1; 4]. Dioxanes are usually reported as oxidation markers in aged fortified and white wines, with an odor described as sweet and similar to old port [60]. Among the terpenic compounds identified, 13 exhibited significant differences (\(p<0.05\)), with higher concentrations observed in the wine sealed with Natural Cork 1. Among the studied compounds, six of them--limonene, camphor, \(\alpha\)-muurolene, cis-calamenene, \(\alpha\)-calacorene, and nerolidol--showed fold changes greater than 0.25. Terpenic compounds are crucial to the aroma of wine, contributing to floral, fruity, citrus, and herbal notes [1; 61]. Natural corks can release small amounts of these compounds into the wine through migration [4]. This was particularly evident with camphor, a bicyclic monoterpene ketone with a distinctive fresh, minty, and eucalyptus-like aroma [12; 13; 62]. Interestingly, camphor was exclusively detected in wines sealed with Natural Cork 1 (Figure 5e), aligning with previous findings that identify it as a key marker of natural cork stoppers [4; 12; 13; 63]. Its presence highlights the migration of volatile compounds from cork during bottle storage. Additionally, three monoterenol oxides--rose oxide, nerol oxide, and linalool-3,7-oxide--were identified. These compounds are oxidation products of terpenic compounds in wine, making them relevant indicators of oxidative processes [64; 65; 66].