Extraction of Phenolic Compounds from Oak Wood in Model Solutions and Evolution of Aromatic Aldehydes in Wines Aged in Oak Barrels

¹ Institut National de la Recherche Agronomique. IPV, Laboratoire des Polymères et des Techniques Physico-chimiques, 9 place Viala, 34060 Montpellier, France.

Bulgarian oak wood released tannins, lignin, and aromatic substances into a model hydroalcoholic solution buffered to pH 3.5, similar to that of wine. A small fraction of lignin (ca 1.8% of that available) was extracted by this model solution, whereas the percentage of tannins extracted amounted to approximately 26% of that available. Among the various products of lignin degradation, vanillin, syringaldehyde, and vanillic and syringic acids were strongly solubilized in response to the acidity of a hydroalcoholic medium (10%, v/v) acidified to pH 3.5 by tartaric acid. The best organoleptic result for Bulgarian Cabernet Sauvignon wines was obtained after 18 months in a 225-L barrel. Vanillin and syringaldehyde contents were 0.34 and 0.86 mg/L, respectively. The best organoleptic result for Bulgarian Merlot wine was obtained after 12 months in a 225-L barrel; the vanillin and syringaldehyde contents were 0.20 and 0.53 mg/L, respectively.