Written by Breakthru Master Cicerone® Dave Kahle
Barrel aging is far from a new concept. It’s origins date back thousands of years to when the Celts developed what we know of as an oak barrel. Wooden barrels are incredibly practical, as they are sturdy, stackable, and can be moved by rolling, which was critical before conveniences like forklifts.
Throughout their existence, barrels have been used to store anything from liquids to grains, meats, salt, hardware, or any bulk goods you might find at a grocery. Consequently, the character that wood imparts to the contents of a barrel were discovered by chance. It’s well known that this wood character became a critical component to wine and many spirits, but certain beers can also benefit from time in a wooden barrel.
Flavors contributed by wood are dependent on the species of wood, where the trees were grown, how the wood was dried or cured, and how much the wood was changed by toasting or charring.
The majority of barrels used for aging beverages are made from White Oak, but we’ve seen a wide range of woods used such as Applewood, Cherrywood, Cedar, Chestnut, Maple, or Palo Santo, among others. There is an amount of terroir that can also be expected from wood within the same species grown in different locations.
It is critical that the wood is allowed to dry before assembling into a barrel. This curing or seasoning of the wood by natural air drying can take 18-36 months. Seasoning reduces certain aldehydes that can smell like a lumberyard but allow for phenolic aldehydes to concentrate and increase notes of cinnamon, vanilla, or clove. The toasting or charring of the wood increases lactones that give the classic coconut flavors to bourbon, but also caramelize cellulose products into toasty, nutty, and caramel character.
If a barrel has heavy charring it can add notes of ash, smoke, bacon or other burnt flavors. All these flavors from wood aging may be secondary compared to the flavors imparted in beer from whatever was previously in the barrel, whether it was wine, spirits, beer or even hot sauce. In the case of sour beers, the microbes that have made the barrel their home become the most important element in developing flavors in a finished beer. Sour styles: Lambic, Gueuze, Flanders Red, and American Wild Ales are almost always getting their acidity from bacteria harbored in the wood.
Sours are most commonly fermented and aged in former wine barrels. Standard wine barrels may be used multiple times for beer, while very large, tall oak barrels called fouders are used repeatedly for decades. Some fouders used in making Flanders Red Ales have been found to have more than 2,000 different microorganisms living in them. If that doesn’t make a complex beer, I don’t know what would.
“More than 200 components of wood may directly contribute to an alcoholic beverage, although only about a dozen are detectable by the human palate,” said Jeff Sparrow, author and founder of Festival of Wood and Barrel Aged Beer.
Brewer’s typically do all they can to reduce the amount of oxygen in their beer, and want their beer consumed as soon as possible after packaging. This logic gets tossed out the window when they put beer in a barrel to age.
Most beer styles have been aged or rested in barrels by modern brewers, but there are only a handful of styles that truly make sense for a barrel. Beers with roasted character, stouts and porters, are well suited to spirits barrels, especially bourbon barrels. The notes of coconut, caramel, vanilla, and spice are a fantastic complement to the coffee and cocoa notes in a stout or porter. Strong beers like Barleywine, Tripel, Dubbel, and Dopplebock have all been barrel aged to great effect. These styles do best with bourbon and rum barrels, although brewers will experiment with former gin barrels or wine barrels. In some cases, they use a blend of multiple different types of barrels for a final product.