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

Abstract

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.