Aroma Potential of Oak Battens Prepared from Decommissioned Oak Barrels

Sijing Li, Anna M. Crump, Paul R. Grbin, Daniel Cozzolino, Peter Warren, Yoji Hayasaka, Kerry L. Wilkinson

Oak maturation plays an important role in the production of wine and traditionally involves aging in oak barrels. During barrel maturation, volatile compounds are extracted from oak wood and impart aroma and flavor to wine, enhancing its character and complexity. However, barrels contain a finite pool of extractable material and so the volatile compounds available for extraction diminish with time. As a consequence, most barrels are decommissioned after 5 or 6 years. This study sought to investigate whether or not decommissioned barrels can be 'reclaimed' and utilized as a previously untapped source of quality oak for wine maturation. Oak battens were prepared from the unused portion of staves obtained from decommissioned French and American oak barrels, and their composition analyzed before and after toasting. The oak lactone glycoconjugate content of untoasted reclaimed oak was determined by liquid chromatography-tandem mass spectrometry and the concentrations of cis- and trans-oak lactone, guaiacol, 4-methlyguaiacol, vanillin, eugenol, furfural and 5-methylfurfural present in toasted reclaimed oak were determined by gas chromatography-mass spectrometry. Aroma potential was then evaluated by comparing the composition of reclaimed oak with that of new oak. Comparable levels of oak lactone glycoconjugates and oak volatiles were observed, demonstrating the aroma potential of reclaimed oak and therefore, its suitability as a raw material for the preparation of alternative oak products, i.e. chips or battens, for the maturation of wine. The surface and interior temperatures achieved during toasting were also measured to evaluate the potential for viable spoilage yeast to remain in reclaimed oak.