Ellagitannins from Portuguese oak wood (Quercus pyrenaica Willd.) used in cooperage: influence of geographical origin, coarseness of the grain and toasting level

Abstract The ellagitannins and ellagic acid from extracts of Portuguese oak wood chips (Quercus pyrenaica) used in cooperage from different origins (Gerês and Guarda forests) were analysed by HPLC. The results were compared with the ellagitannin content of wood chips obtained from American (Q. alba) and French (Q. petraea) oak. The influence of heat treatment and the coarseness of the grain on ellagitannins and ellagic acid were also studied. Five ellagitannins (vescalagin, castalagin, roburin D, roburin E and grandinin) and ellagic acid were quantified. Vescalagin and castalagin were the most abundant individual ellagitannins in all of the oak wood chips studied. Portuguese oak wood had the highest content of ellagitannins and ellagic acid, followed by the French and American oaks. The geographical origin of Portuguese oak and the coarseness of the grain of French oak affected the content of ellagitannins and ellagic acid. In general, the ellagitannin content decreased with the toasting process, while the ellagic acid content increased. The toasting process had the highest impact on ellagitannin composition in comparison to the other variables studied.