NMR-based metabolomic tools for quality control and authenticity assessment of wines aged with alternative wood products

Abstract

The increasing use of alternative wood products (e.g. chips, staves and large oak vessels) in enological aging practices raises relevant issues related to quality control, traceability and authenticity assessment, particularly in the context of regulatory monitoring. Analytical approaches capable of providing robust and reproducible compositional fingerprints of wines are therefore required. Nuclear Magnetic Resonance (NMR) spectroscopy represents a powerful, non-destructive technique for untargeted metabolomic characterization of complex matrices such as wine. This work evaluates the potential of an NMR-based metabolomic approach combined with multivariate statistical analysis for the assessment of alternative wood aging practices, with a specific focus on applications related to quality control and authenticity. Preliminary trials involved the characterization of French oak chip extracts with different toasting levels, obtained through optimized Soxhlet extraction protocols and supported by the analysis of reference standards of key wood-derived compounds. Subsequently, hydroalcoholic model solutions (12 % v/v ethanol, pH 3.2) and experimental monovarietal wines were treated with alternative wood products under controlled conditions (3 g/L; 45 days). The experimental wines included four grape varieties (Nebbiolo, Barbera, Pinot noir, and Merlot) subjected to different aging modalities, namely chips, barrique, large oak vessels, staves and untreated controls. 1H NMR spectra were acquired at 600 MHz following standardized sample preparation procedures, and spectral data were processed using bucket integration and principal component analysis (PCA). Multivariate analysis highlighted a clear discrimination among grape varieties, confirming the dominant influence of varietal composition on the global NMR metabolomic profile. In contrast, separation among different wood aging treatments was less pronounced, although partial trends were observed for barrique-aged wines. These results indicate that, under the applied conditions, varietal effects outweigh the impact of alternative wood aging in untargeted NMR-PCA models. Overall, NMR metabolomic fingerprints appear suitable as a screening tool for wine authenticity and quality control, while the discrimination of specific wood aging practices requires the integration of supervised chemometric models and complementary targeted analytical techniques.

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