“Our results indicate that q-NMR metabolomics enables the differentiation of Médoc and Libournais vineyard
highlighting the most discriminant constituents”
Almost half of the total value of exports of French Protected Designation of Origin (PDO) wines is an account for by wines from the Bordeaux region of France. Indeed, Bordeaux is a leading wine-producing area with nearly sixty PDO areas. The Bordeaux PDOs are categorized into five main subdivisions: Médoc, Graves, Libournais, Entre-deux-Mers, and Blaye-Bourg. This reflects the great importance that is placed on the area of grape cultivation in Bordeaux. It is even considered more important than the grape varietal used. This is highlighted by the fact that wines from grapes grown on one side of the River Gironde are distinguished from those produced on the other side.
The main cultivar of Bordeaux vineyards is merlot, but cabernet sauvignon and cabernet franc are also widely used. Some vintners add small amounts of other red grape varieties such as Malbec, petit Verdot, or Carmenere to achieve the taste they require. Within the Bordeaux wine-growing community there is a strong desire to be able to distinguish between wines from different regions. Wines have been successfully discriminated by geographical origins, grape varieties, or vintages using nuclear magnetic resonance spectroscopy (NMR). Indeed, NMR has been adopted as a tool for confirming the authenticity of wines. Such metabolomic analysis has now been taken one step further and is has been assessed for the ability to classify wines from different areas within the Bordeaux region.
NMR using a Bruker 600 MHz spectrometer was used to analyse 224 red wines from the main French DPO regions (Bordeaux, Beaujolais, Burgundy, Côtes du Rhône, Languedoc-Roussillon, and Loire Valley) and of different vintages (2004–2017). The Bordeaux wines tested were from six different Bordeaux appellations (Bordeaux generic, Blaye and Bourg, Entre-deux-Mers, Graves, Libournais, and Médoc).
The NMR fingerprints of the different wines were then compared to assess how easily Bordeaux wines could be discriminated from the other French PDO wines and from other Bordeaux wines. Effects of bottle aging and vintage on the NMR spectra of Bordeaux red wines were also explored.
Differences in the concentrations of the forty compounds identified in the wine samples enabled Bordeaux wines to be classified and distinguished from the other French wines with 95% accuracy. Compared with other French wines, Bordeaux red wines had higher levels of proline, phenethyl alcohol, and succinic and gallic acids. Furthermore, NMR analysis successfully, differentiated wines from the two major Bordeaux sub-regions Libournais and Médoc. Médoc wines contained high levels of lactic acid, whereas Libournais wines contained more ethanol. The differences between these areas of Bordeaux were found to be a reflection of grape variety composition as well as soil type and viticultural practices.
NMR spectra revealed a clear evolution in wine composition during bottle aging, making it possible to discriminate between wines of similar vintages according to their age.
NMR metabolomic analysis thus provides a powerful tool for the differentiation of wines according to the vineyard from which they originated, the vintage, and the duration of bottle aging.
Gougeon L, et al. Food Chemistry 2019;301:125257. https://doi.org/10.1016/j.foodchem.2019.125257