Determination of Chardonnay oxidative susceptibility through Strecker aldehyde quantification and Spin-Trap/EPR spectroscopy

Abstract

Oxidative susceptibility of Chardonnay wines (CW) governs aging potential and quality. Consequently, the wine industry seeks robust strategies to predict it. During bottle aging, upstream of white wine oxidation involves Fenton-type chemistry along with the formation of hydroxyl radicals (•OH) and the 1-hydroxyethyl radical (1-HER). Such oxidation is also associated with the formation of Strecker aldehydes (SA) (Escudero et al., 2000), notably methional (MET) and phenylacetaldehyde (PHE). Additionally, SA could be released during oxidation from bound forms (Bueno et al., 2016). Based on current knowledge, this work combines 1-HER kinetic (K-1HER) study using Spin Trap/EPR technique with quantification of SA to evaluate the oxidative susceptibility of CW. We selected fifty CW spanning largely oxidative status from 1998 to 2022 vintages. Free and total SA were quantified by GC-MS, while K-1HER were monitored using Spin Trap/EPR methods to calculate the index a, which integrates the peak area and peak width of the kinetic profile (Han & Pons, 2025). On average, total (free + bound) MET and PHE varied widely across wines (22.1 ± 14.2 µg/L and 24.6 ± 13.8 µg/L, respectively). In oxidized wines, we showed that total MET correlated with free MET level (r = 0.77) and index a correlated with free MET (r = 0.58). These observations were then confirmed in 38 additional CW under controlled accelerated aging (AAg). Higher initial bound MET levels were associated with higher free MET levels after AAg. Indicating that the bound fraction can serve as a potential predictive indicator. Moreover, we demonstrate for the first time that the increase in MET is consistent with the rise in index a (49.8 %), confirm that K-1HER reflect oxidation progress. Furthermore, using two complementary spin traps (POBN and DMPO) selective to radicals, we confirmed that both 1-HER and •OH contribute to MET formation, providing mechanistic support for this aspect. We propose, combining EPR signatures along with free bisulfite content, as a potential indicator to estimate shelf life in CW under AAg conditions. Overall, this work outlines an integrative strategy to predict oxidative susceptibility in CW. Of course, additional investigations and validations under different bottle aging conditions are required.

References

Bueno, M., Carrascón, V., Ferreira, V., 2016. Release and Formation of Oxidation-Related Aldehydes during Wine Oxidation. J. Agric. Food Chem. 64, 608–617.

Escudero, A., Hernández-Orte, P., Cacho, J., Ferreira, V., 2000. Clues about the Role of Methional As Character Impact Odorant of Some Oxidized Wines. J. Agric. Food Chem. 48, 4268–4272.

Han, P., Pons, A., 2025. Electron paramagnetic resonance (EPR) spin trapping applied to Chardonnay wines: impact of phenolic content and ethanol. Current Research in Food Science 12, 101276.