Oak has been used for centuries to make casks for ageing spirits like whisky. It's an ideal material, as it is dense, durable, and water-resistant (particularly important when filling it with delicious spirits!). The type of oak used to make casks can influence the final flavour profile of the aged whisky. In whisky production, th two main species of oak most commonly used are American White Oak (Quercus Alba) and European Oak (Quercus Robur).
American White Oak, Quercus Alba
American White Oak is primarily used for bourbon production in the US. American White Oak, scientific name Quarcus Alba, is known for its high tannin content and flavour notes of vanilla and caramel. The wood is harvested from trees that are typically around 100-150 years old. It is then air-dried for up to two years before being used to make casks by skilled coopers. During the drying process, the wood loses moisture and the flavours become more concentrated. Once the wood has been coopered into barrel form, it is toasted to further enhance the flavours, and then charred to create the desired level of caramelization. The charred oak also helps to remove impurities from the whisky as it matures.
By US law, whisky casks can only be used once in the bourbon industry. But, there's still plenty of flavour in these barrels. So, rather than them going to waste, the bourbon industry will export them to Scotland. Here they can then be refilled and used to age scotch whisky.
European Oak, Quercus Robur
European Oak is often used for the production of sherry and wine casks. This species of oak, Quercus Robur, is known for its notes of spice, nuts, and dried fruit. The oak trees used for European oak casks are typically around 200-300 years old and are harvested from forests in France, Spain, and Portugal. The wood is also air-dried for up to two years, and then seasoned to bring out the flavours. Unlike American White Oak, European Oak has a lower tannin content and so can be used for ageing whisky for a longer period.
The casks used to age Scotch whisky are typically seasoned with sherry or wine before being filled with new spirit. This helps layer further flavours into the maturing whisky.
Other species, like Mizunara Oak
While American White Oak and European Oak are the two most common woods used to make whisky casks, there are other species of oak used in different parts of the world for the production of whisky casks. For example, in Japan, Mizunara Oak is sometimes used for ageing whisky. Mizunara Oak has notes of sandalwood, coconut, and spice. But, it is extremely hard and difficult to work with, making the casks - and in turn the whiskies - more expensive.
Ageing whisky in oak casks
The type of oak used to make whisky casks can greatly affect the final flavour of the aged whisky. American White Oak is known for its high tannin content and flavours of vanilla and caramel, while European Oak imparts notes of spice, nuts, and dried fruit. These are the two styles of whisky cask that we specialise in here at Spiritfilled. If you'd like to see the whisky casks we have available, please contact us here.