Eugenol:  a new marker of hybrid vines? The case study of Baco Blanc in Armagnac

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 actual 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 resisted 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 vine and productive vine of white wine intended for distillation (Baco, 1925).

Armagnac white brandies elaborated with only Baco Blanc present an atypical chemical profile. Eugenol, a phenylpropenic compound, usually known to be released by contact with oak, is significantly more concentrated in white brandies made with Baco than same products made with V.vinifera cultivars. Moreover, eugenol has been identified in other hybrid vines (Sun et al., 2011). Pure form of eugenol has a clove aroma and a noticeable and well-known antiseptic action, a gustative impact including an anesthesic power. These observations raises plenty of questions but the main ones are: “Is there a link between tolerance of the 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?”.

Thus, we quantified eugenol in plants, grapes, musts, wines and distillates by HS-SPME-GC/MS. In grapes, a greater eugenol concentration and accumulation during maturation occurred in Baco Blanc than in other V.vinifera cultivars we tested (Ugni Blanc and Folle Blanche). In Baco Blanc wines, the use of enzymes increases the eugenol content during first steps of winemaking and highlights the existence of both eugenol forms, bounded and free fractions. Furthermore, eugenol amounts seemed 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.