Assessment of oxidation compounds in oaked Chardonnay wines: A GC-MS and 1H NMR metabolomics approach

The oxidation of oaked Chardonnay wine during long-term storage was studied by headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC/MS) and proton (1H) nuclear magnetic resonance (NMR) spectroscopy. Three distinct groups of wine were defined based on the browning index: control, least oxidized (OX1) and most oxidized (OX2). HS-SPME-GC/MS and 1H NMR spectroscopy enabled the profiling of a total of 155 compounds in all wine samples including aldehydes, ketones, esters, polyphenols, among other classes. Acetaldehyde, 3-methylbutanal, 2-phenylacetaldehyde, methional, 3-penten-2-one, β-damascenone and four unknown carbonyl compounds showed the highest percentage of variation with oxidation. Novel oxidation markers found in this work include pentanal, 3-methyl-2-butanone, 3-penten-2-one, 2-methyltetrahydrofuran-3-one, β-damascenone, ethyl 2-methylbutanoate and vinyl decanoate. In addition, several correlations between polyphenols, aroma compounds and absorbance at 420 nm (A420) were observed, suggesting the occurrence of chemical reactions with a possible impact in wine browning.