Quantification of Eugenol in various matrixes from hybrids vines. Case study of Armagnac white spirits production

Abstract

Nowadays, winemaking is dealing with great challenges, notably climate change, disease resistance and low pesticide inputs, desire for more sustainable agricultural productions and permanent changing of consumer preference. Trying to propose practice improvements, scientists are exploring vine hybridization a paradoxically old but still promising way to take up such challenges (Pedneault & Provost, 2016). Phylloxera crisis in Europe (XIXth century) was a crucial step for improving hybridization in grapevine. Unfortunately some of the wines produced then presented redibitory sensorial default and were finally excluded for getting the PDO (Protected Designation of Origin) wine label in France.However, one grape variety from Armagnac vineyard was maintained despite the ban: the Baco blanc, a complex hybrid of Vitis labrusca x Vitis riparia x Vitis vinifera. Baco was created to be a disease tolerant and productive vine of white wine intended for distillation (Baco, 1925).Various matrixes, from vine shoots to distillates, are available for analysis in Armagnac wine spirit production. It was noticed that Baco blanc samples (all matrixes included) had an atypical chemical profile. Indeed, eugenol, a phenylpropenic compound, usually known to be extracted by contact with oak, is significantly more concentrated in white spirits made with Baco than same products made with V.vinifera cultivars. Eugenol was also quantified in other hybrids (Vitis riparia-containing hybrids as Marechal Foch and Frontenac) wines but in lower concentrations than in Baco blanc wines (Sun et al., 2011).Eugenol has a clove aroma and a noticeable and well-known antiseptic action, a gustative impact including an anesthesic power. These observations raise many questions, the main ones being: “Is there a link between tolerance of Baco to diseases and the presence of eugenol?”; “What is the dynamic of eugenol levels during spirit making?”; “Is there a link between the eugenol presence and the typicity of Baco wine spirits ?”Trying to answer these questions eugenol quantification was carried out by a HS-SPME-GC-MS method using deuterium labelled eugenol as internal standard and a procedure adapted to each matrix. An enzymatic hydrolysis (β-glucosidase enzyme) with addition of citrate-phosphate buffer was performed for plant material, musts and wines. The main goal was to highlight the existence of two eugenol fractions : a free one and a bound one. Such eugenol « cartography » resulted in interesting observations. First a greater eugenol concentration and accumulation during maturation occurs in Baco blanc than in other V.vinifera cultivars tested (Ugni blanc and Folle blanche). Second using enzymes increases the eugenol content during first steps of winemaking. Third, eugenol amounts seem to increase along with the storage duration on lees (before distillation). Finally, alambic characteristics may influence the alcohol content which may also impact eugenol concentration.

References

Baco, F. (1925). Précis complet de viticulture moderne et de vinification : Mes meilleures vignes hybrides franco-americaines : leurs principaux caractères : les meilleurs moyens pour les multiplier, les planter, les tailler, les cultiver, les vinifier (Imprimeries Gounouilhou)
Pedneault, K., & Provost, C. (2016). Fungus resistant grape varieties as a suitable alternative for organic wine production : Benefits, limits, and challenges. Scientia Horticulturae, 208, 57-77. https://doi.org/10.1016/j.scienta.2016.03.016
Sun, Q., Gates, M. J., Lavin, E. H., Acree, T. E., & Sacks, G. L. (2011). Comparison of Odor-Active Compounds in Grapes and Wines from Vitis vinifera and Non-Foxy American Grape Species. Journal of Agricultural and Food Chemistry, 59(19), 10657-10664. https://doi.org/10.1021/jf2026204