Have you spotted the words "barrel aged" on some of the more expensive beers recently?
With their proclivity for innovation, a number of American craft brewers have stepped backward in the name of progress. For many decades, brewers had adopted hygienic materials in the brewery, particularly stainless steel, but some have returned to aging their beer in trouble-prone wood for a depth of flavor that sterile metals can't provide.
In taking up wooden barrels, brewers are reverting to traditional technology that was a part of the craft for centuries until it was supplanted by easier-to-clean copper and steel. A marked improvement on the breakable and cumbersome ceramic amphorae that preceded them, barrels were a marvel: durable and constructed with a remarkable precision that was perfected early and never really improved upon. The round circumference made rolling easier; the bowed middle made them more maneuverable.
By the Middle Ages, the wooden barrel was well established in European feudal culture. The oldest surnames in the English language reflect the central occupations in village life at that time: The arrow-maker took the surname Fletcher, the stoneworker was called Mason and the local barrel-maker was known as Cooper, a term still used today.
Oak was, and is still, the wood of choice for barrels, abundant in the forests of Europe and America and prized for the range of sweet, complex notes it can contribute to a liquid stored in it.
Although some brewers have sought out wine barrels for more delicate flavoring, the bulk of barrel-aged beer relies on casks obtained from distillers, with bourbon being the most popular.
American white oak, Quercus alba, is a more robust oak than the European species conventionally used for wine barrels. The wood for spirit barrels is quickly kiln-dried, which leaves behind many of the strong flavoring compounds. Then the barrel is constructed, and the interior is charred—set on fire—to the distiller's specification.
When the barrel is completed, the heavy layer of char and underlying layers of toasted wood are ready to permeate a relatively neutral spirit with color and a super dose of favor: vanilla, caramel, almond, coconut and "oakiness," augmented with smoke, cedar or coffee notes.
By law, bourbon must be aged in new American oak barrels, so bourbon distillers say goodbye to thousands of once-used casks every year. Permeated now with the potent flavor of the spirit itself, these barrels make their way to new roles aging Scotch, Irish and Canadian whiskies; rum, tequila, sherry and—since the mid-1990s—beer.
Goose Island's Bourbon County Stout from Chicago's Goose Island Brewery was the first in a growing collection of barrel-conditioned beers.
The most popular beer styles for bourbon barrel aging are those that are dark, malt-accented, fairly muscular and able to stand up to the potent influence of bourbon. Paul Philippon, founder and brewer of the Duck-Rabbit Craft Brewery in Farmville, N.C., terms his brewery "the dark beer specialist." His rich Baltic porter was a natural for bourbon aging, netting Duck-Rabbit a national medal.
"We've been getting our barrels from the Pappy Van Winkle distillery in Kentucky," Philippon says. "I love their bourbon. Even though I don't make it, I'm almost as much of a bourbon guy as I am a beer guy."
The barrels arrive with the precious black char intact, or nearly so: Remnants are knocked free with a mallet. Philippon uses each barrel for six or seven batches of beer, by which time the bourbon influence had faded.
Jamie Bartholomaus of Foothills Brewing in Winston-Salem has also won national awards for potent, barrel-aged beers. His brewery's annual release beer, Sexual Chocolate Imperial Stout, is already a cult favorite. The barrel-aged edition is so rare that Foothills doesn't even sell it: They give it away, pouring it at festivals to reach the maximum number of people.
Bartholomaus explains "If we don't make enough and you sell it to one guy, then bars two, three and four aren't happy. But they can't get upset if you just give it away."
Bartholomaus, president of the state's brewers' guild, was part of a three-brewery collaboration that produced a crazy, complex beer this year. Foothills, Duck-Rabbit and Olde Hickory breweries each created a massive stout, then aged it in barrels before blending and bottling. The finished beer, Olde Rabbit's Foot, was released in December to devoted fans who queued overnight for a chance to purchase bottles.
If you're lucky enough to find a bottle (please share it!), expect a rich, roasty beer with chocolate notes that boasts an admirable balance between the stout character and the bourbon influence. But if you missed this particular beer, treat yourself to one of the more widely available barrel-aged beers. At their best, they are beautifully complex, dessert in a glass: a tribute to the combined powers of living beer and living wood.
Julie Johnson is the editor of All About Beer Magazine. E-mail her at email@example.com.