Characteristics of Oak Wood and Biochemical Aspects of Armagnac Aging

Abstract

Several varieties of oak wood from France or other countries were analyzed for their biochemical compositions in lignin and tannin. The analysis of hydroalcoholic extracts from such wood shows that a small fraction (3% to 5.8%) of the lignin pool is extracted, while tannin extraction, which is more intense, represents 41% to 66% of the initial tannin content of oak wood. Using a stave from a barrel that had contained Armagnac for 80 years, it was attempted to determine the gradient of lignin and tannin extraction in relation to the Armagnac penetration into wood. The optimum extraction of these phenolic compounds by hydroalcoholic solutions, having an alcohol content of 40% to 72% alcohol (v/v), was evaluated. The conditions of lignin degradation, in the case of Armagnac stored in oak barrels, were determined by HPLC allowing the identification of coniferyl alcohol and Hibbert's ketones. A pattern of lignin degradation is proposed on the basis of the findings.