Oak Lactone Formation in Wine and Spirits: the Role of Glycosidic Precursors

The use of oak as a medium for the fermentation and/or maturation of alcoholic beverages is long established. Oak possesses a unique combination of physical and structural properties, which make it ideal for barrel construction. Additionally, oak maturation plays a significant role in the production of wine and spirits, influencing both physical attributes (colour, stability and astringency) and sensory characteristics. Of the many oak-derived volatiles extracted during maturation, the most important are considered to be the cis- and trans-isomers of oak lactone. Despite their importance to the aroma and flavour of wine and spirits, their origin remains unclear. Oak lactone is present in green oak wood, but additional quantities can be generated during the seasoning and toasting processes of cooperage, suggesting the presence of one or more precursors. This work describes: the role of glycosidic precursors in the formation of oak lactone during cooperage and maturation; the sensory impact of cis-oak lactone; and the kinetics of oak lactone formation and shortcomings of using oak chips/shavings as expedient alternative to barrels.