Philippine de FERRON, Cécile THIBON, Svitlana SHINKARUK, Philippe DARRIET, Alexandre PONS
Bordeaux University - Institut des Sciences de la Vigne et du Vin - Unité de Recherche Oenologie
Email contact: philippine.de-ferron[@]u-bordeaux.fr
Wine flavor results on complexes interactions of odorous components, which come from different aromatic families like esters, thiols, aldehydes, pyrazines or lactones. Varietal lactones identified in red wines contribute to cooked fruity flavors such as dried peach, apricot, figs and dried prune. Recent studies have demonstrated the key impact of the harvest date on the lactone content in wine. The influence of the temperature during grape ripening was also underlined. Many lactones have been detected in wines, but one of them, γ-nonalactone, possesses a low detection threshold (Dth 27 µg/L), and has been detected at high concentration in wine (up to 200µg/L;).1,2 Thus, it contributes directly to the cooked peach flavors in red wines.
All these observations led us to investigate the chemical and biochemical mechanisms associated with γ-nonalactone formation in must and wine. Based on Tressl et al.,3 work realized in beer, we hypothesized that 4-oxononanoic acid was a potential precursor of γ-nonalactone in wine. To study its occurrence in musts from Merlot and Cabernet Sauvignon grapes, a GC-(NCI) MS method was developed and validated. 4-oxononanoic acid is identified for the first time in must samples whereas its concentration was ranged from some µg/L to more than 60 µg/L. Additionally, in order to demonstrate the impact of alcoholic fermentation on the formation of γ-nonalactone, we synthesized labelled d6-4-oxononanoic acid and observed a positive correlation between d6-4-oxononanoic acid concentration added and d6-γ-nonalactone formed in spiked samples.
In conclusion, our results demonstrated the presence of 4-oxononanoic acid in must and its biotransformation to γ-nonalactone during alcoholic fermentation of red grape varieties. We validate for the first time its role of precursor of the odourous γ-nonalactone in wines.
(1) Allamy, L. Recherches sur les marqueurs moléculaires de l’arôme de `` fruits cuits ’ ’ des raisins et des vins rouges issus des cépages Merlot et Cabernet-Sauvignon: Approches sensorielle, analytique et agronomique. 2015, Université de Bordeaux
(3) Tressl, R.; Friese, L.; Fendesack, F.; Koeppler, H. Gas Chromatographic-Mass Spectrometric Investigation of Hop Aroma Constituents in Beer. Journal of Agricultural and Food Chemistry 1978, 26 (6), 1422–1426.