As the world of whisky has grown there has been an ever-more interesting array of casks used for maturation and finishing to produce new flavours and experiences for the drinker. Certainly, the use of heavily charred virgin oak is legally required in bourbon production, and those same barrels, once used, form the oaken backbone of most of the world’s great single malts and blends. But producers are gradually gravitating towards other casks to put unique spins on traditional flavours. Whether it be casks that formally contained different wines or spirits, alternative oak species, or entirely different woods altogether, the modern whisky flavour spectrum is benefiting from an influx of new and innovative ideas.
Cask chemistry is one of the more complicated subjects in the world of whisky. While research is continuous, there is much that beverage scientists still don’t fully understand about the whisky maturation process. Something that is definitely known, however, is that casks effectively provide two categories of reactions. First is the addition of compounds. This may be from simple extraction of woodthe absorption of sulphur compounds such as dimethyl sulphide into a cask’s carbon char layers as well as the chemical reduction of peppery-tasting acrolein to the comparatively tame acrylic acid. These chemical reactions form the basis for the maturation process and have a notable impact on a whisky’s aromatic and flavour profile (although some modern distillers are attempting to debunk the assertion that “most” of the character comes from the cask).
