Detection of markers from premature wine oxidation (or random oxidation) of white wines closed with cork stoppers

To date, cork is the most important material for wine bottles closures: it is sustainable and offers to users the most natural way to seal wine. Despite its specific physicochemical properties, the variability among natural cork stoppers is a controversial issue because of random or premature wine oxidation (POx) cases. This phenomenon occurs when a wine with aging potential is found to be oxidized and often undrinkable. POx markers identification, reliable methods for their detection in wine, and correlations between POx markers and the system “wine-bottle-closure” (WBC) are still unknown. This paper aims at detecting POx markers in 5 white wines bottled with natural corks, and stored upright under controlled temperature and humidity conditions, and to search for relationships between POx and WBC. To detect POx markers, a non-targeted screening was performed on a metabolomics platform constituted of a hybrid quadrupole-time-of-flight mass spectrometer coupled to a UHPLC chromatographic system. Investigations on WBC system included the analyses of sulfur dioxide, volatile acidity, acetaldehyde, color, appearance and aroma, physical and mechanical parameters of stoppers, headspace and bottle neck inner profile. Statistically, the analytical data were treated with ANOVA, fold-change analysis, PCA and PLS-DA. Firstly, ANOVA results from metabolomics analysis outlined the grouping of the samples depending on wine type, and within each one, separation according to the POx intensity (low-medium-high oxidation level) was evidenced. Then, PLS-DA performed using all the data highlighted three homogeneous groups each comprising the different wines and listing those compounds with a significant discriminating capacity toward POx intensity. Finally, correlations were attempted between the POx intensity and the parameters belonging to the WBC system.