It’s Beer Fact Friday again. Let’s talk about barrel-aging.
Once upon a time, most (if not all) beer spent at least some time inside a wooden barrel. Before stainless steel became the material of choice for fermenting beer without imparting additional flavors, brewers used what they had available: wood barrels, usually made of oak. Before any beer went inside, brewers would commonly fill these barrels with boiling water or acid to remove any wood flavor; only once it had been rendered neutral was it thought fit to hold beer.
In contrast to their forefathers, modern brewers mainly age beer in barrels for the express purpose of infusing their creations with additional flavor and character. To do this, brewers select from a variety of vessels: ones built of American oak, French oak, cedar, palo santo wood and more, and ones that held a panoply of beverages and foods, from bourbon, wine and tequila to hot sauce and maple syrup.
The most common oak vessel found at breweries today is the bourbon barrel, and there’s a good reason for this outside of the fact that the flavors of bourbon mesh delightfully with malt-focused styles like imperial stout, barleywine and Scotch ale. By U.S. law, whiskey makers who want to call their creation “bourbon” must age their liquid for a minimum of two years inside brand-spanking-new American oak barrels, meaning a barrel can only be used once in the process of making true bourbon. This means there are a lot of barrels floating around whiskey distilleries that are of no use to bourbon-makers, but are of great use to brewers.
Well-managed barrel-aging can transform the beer inside the oak into something completely different. Beer left to rest inside a bourbon barrel, for instance, will usually pick up flavors of caramel, toffee and brown sugar from the whiskey as well as notes of vanilla and toasted coconut from the wood itself. But flavor isn’t the only thing that changes: Most barrel aged beer will also pick up some alcohol content. Many barrels arrive at our brewery with some liquid still sloshing around inside—to say nothing of the spirit trapped inside the wood. As it ages, the beer absorbs this residual liquid, gaining in ABV. Barrel-Aged Kilt Lifter, for instance, usually jumps a couple percentage points in ABV after its time inside bourbon barrels is done.