The influence of wood species of casks on matured whisky aroma : identification of unique character imparted to whisky by casks constructed of Japanese oak

Traditionally, whisky is matured in casks made of oak and the aroma is greatly influenced by wood species. Currently, the predominant cask types used are those of either American or European oak. In Japan, in addition to these types of cask, a small number of Japanese oak casks have also been used. Maturation in Japanese oak is known to give unique coconut aromas. The aim of this research was to identify the unique coconut aromas imparted by Japanese oak. The sensory properties of Japanese oak whiskies were investigated in comparison with whisky matured in American and European oak casks with particular attention to lactone isomers known to have a coconut aroma. Whiskies matured in Japanese oak casks were found to develop substantially higher levels of trans-lactone relative to whiskies matured in either American or Spanish oak. This research focused on the influence of lactone isomers and found the possibility of a synergistic effect between the isomers on coconut aroma. Further investigation on the impact of heat treatment on regeneration of casks determined that colour and aromatics were generated, while lactones were not regenerated once the levels had been depleted by a period of maturation