Inside the Barrel

New Brewers and Old Oak

January 1, 2010 By Julie Johnson

In 1994, Chicagoans were treated to an extraordinary beer created to celebrate the 1,000th batch brewed at the Goose Island brewpub: Bourbon County Stout, an intense, black stout that brewer Greg Hall had aged in oak barrels fresh from the Jim Beam bourbon distillery.

The following year, brothers-in-law Adam Firestone and David Walker sat in the Firestone Vineyard in central California, surrounded by family wine barrels, planning a new craft brewery that would be distinguished by the use of oak barrels to ferment their beer.

And in 1996, Belgian brewer Peter Bouckaert moved from renowned Rodenbach brewery in Flanders to New Belgium Brewing Co. in Colorado, bringing with him the traditional skills to manipulate the souring and conditioning of beer in oak barrels.

Now, 15 years on, American brewers are eagerly exploring the possible interactions between maturing beer, permeable wood and microorganisms. The popularity of “wood-aged” beer rivals the growth of double and imperial styles of a few years ago. At the medal competitions at the Great American Beer Festival, the bellwether of evolving beer styles, the first wood-aged category appeared in 2002 with 26 entries. By this year’s competition, wood- and barrel-aged beer had been divided into three main categories, with 188 entries between them. (For comparison, the three main “imperial” categories attracted 169 entries.)

But even as beer drinkers are embracing some of the extraordinary wood-influenced flavors these new beers have to offer, the different lineages of the beers and their barrels are every bit as intriguing. The three pioneering efforts of the mid-’90s in Chicago, California and Colorado reflect three different trends that are distinct―even as some brewers are now combining them in creative new ways.

Barrel History

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.

Of course, barrels themselves were a marked improvement on the ceramic amphorae that preceded them, which were breakable and cumbersome. 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, and the bowed middle made them more maneuverable. Barrels may have been an invention of the Gauls―perishable wooden artifacts don’t last well enough in the archaeological record to say―but it’s clear that the Romans were using barrels at least 2,000 years ago.

Several centuries later, the wooden barrel was well established in European feudal culture. The oldest surnames in the English language, dating back to the medieval era, 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 then and is still the wood of choice for barrels, prized for the range of sweet, complex notes it can contribute to a liquid stored in it. But it’s likely that oak’s flavoring properties were secondary in establishing its dominance owing to its abundance in European and American forests and its suitability to the cooper’s needs. It’s pure luck for us today that the most appropriate wood for the medieval craftsman’s tasks could later be exploited for its flavor by winemakers, distillers and brewers.

Two Coopering Traditions

It wasn’t until the 17th century that European winemakers came to appreciate the contribution of wooden oak barrels to the flavor of their contents, and began to adjust the manufacture of barrels to enhance the most desirable traits. And across the Atlantic, coopers in the New World applied their Old World skills to the crafting of barrels from a different species of oak, harvested from the vast American white oak forests.

In time, two related traditions of coopering grew up, one to serve primarily the European wine industry, and the other to cater to American distillers. The differences between them persist today, as the makers of alcoholic beverages, including brewers, still put them to specific uses.

The difference starts with the trees. French oak―technically either Slovenian oak (Quercus robur) or sessile oak (Q. petraea)―the traditional choice for wine barrels, has a fine grain and high porosity. Because of the nature of the wood, French oak has to be hand-split along the grain, which preserves capillaries in the wood. American, or white oak (Quercus alba) is a more robust tree, and American loggers saw, rather than split, the logs, probably permitting stronger flavors to eventually leach out of the barrels.

“The difference between French oak and American oak is also the difference between a wine barrel and a bourbon barrel,” explains Paul McLaughlin of Kelvin Cooperage. The Kentucky company was founded by his father, a cooper trained in Scotland. “The key is that the wood for a wine barrel is air-dried for at least two years before they make it. The idea is that you allow the wood to sit out in the elements, exposed to wind, rain and sun, and you’re leaching out the harsh tannins―the more astringent elements that you can get in a really oaky wine that makes your lips pucker.”

The American oak, by contrast, is quickly kiln-dried, with more of the stronger compounds remaining behind. This difference only becomes accentuated as the cooper constructs the barrel.

Once the staves―the long boards that make up the sides of the barrel―are raised into a barrel shape and secured in place, both types of barrels are heated to cultivate the right flavors in the wood. “The big difference in wine versus whisky is that with a wine barrel you slowly toast the barrel over a small oak fire where it can sit for up to an hour,” says McLaughlin. “With a whiskey barrel, you’re going to char it heavily, usually over a gas element: you’re literally setting the inside on fire. The char gives it a smoky flavor, something on a wine barrel you’d avoid. The key difference, of course, is that whisky can handle a lot more than wine can.”

After testing the barrels for liquid-tightness, the barrels are sent to their first users. The French wine barrels arrive precisely toasted to maximize the oak flavors that emerge at different heating regimes to favor vanilla, caramel, almond, coconut and “oakiness.” The American bourbon barrels, with their 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 those same flavors, augmented with smokiness, cedar or coffee notes.

New Oak for Bourbon

By law, bourbon must be aged in new American oak barrels. Whether the hand of the cooperage industry was behind this statute or not, the requirement means that the flavor of bourbon is really the flavor of new oak. “What is bourbon flavor?” asks Matt Brynildson, head brewer at Firestone Walker Brewing Co. “It’s essentially a spirit that’s picked up massive amounts of oak flavor―when I taste bourbon, I taste toasted oak juice.”

“Bourbon barrels can only be used once. So, really, it’s bourbon that stands out as the unique industry because they have to use new oak―kind of like the Reinheitsgebot of distilling.”

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 whisky, Irish whiskey, Canadian whiskey, rum, tequila, sherry and―since the mid-1990s―beer. Goose Island’s Bourbon Country Stout and the beers it has inspired have become the largest category of barrel-touched beers.

The most popular beer styles for bourbon barrel aging are beers 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 North Carolina, terms his brewery “the dark beer specialist.” His Baltic porter was a natural for bourbon aging, netting Duck-Rabbit a GABF medal.

“We’ve been getting our barrels from the Pappy Van Winkle distillery in Kentucky,” he 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. “We collect those,” chuckles Philippon, “which collection I hope eventually to use to smoke some ribs … .”

What follows next is part science, part mystery, as everyone who works with wood agrees. “Once our beer has gone into these barrels, the question is how much we can manipulate what happens next, and the answer is practically none at all,” says Philippon. “What we can do is taste it periodically. I feel I’ve tasted a number of commercially available beers aged in wood that have gone further than I’d care to go, that have more of the bourbon flavor than I prefer. So I try to be very careful to get the amount that I want and no more.”

Philippon finds he can fill and empty a barrel about three times before the oak/bourbon effect tails off.

He is quick to say he’s not an expert when it comes to barrels, despite his critical success in the category. “We are to some extent flying by the seat of our pants. We do small quantities in the bourbon barrels. It’s a way to interject something fun and different, and use beer we already have to play a little.”

Barrels from Wine

While ex-bourbon barrels migrate into the beer world for a few sessions of amping up beers that are pretty big to begin with, former wine barrels can have a different fate. Here, the brewer is working with a barrel whose flavors were more restrained to begin with, possibly by the nature of the oak species, possibly by national character and certainly through the cooper’s art. These barrels can be a source of subtler flavors, or a home for a whole new community of fermentation bugs.

At Cascade Brewing Co. in Portland, OR, brewmaster Ron Gansberg has drawn on a background in both wine and beer-making to design a barrel-aging program that will soon feature over 300 barrels in a facility designed for the aging and blending of sour beer. All Gansberg’s beers are devoted to “bugs”―atypical microorganisms that can affect the flavor of beer, and many of which do particularly well in wooden barrels.

In the tradition of some Belgian beers, which Peter Bouckaert of New Belgium Brewing Co. helped to launch in this country, a few American brewers are cultivating organisms in their breweries that would have inspired nightmares for brewers a generation ago―Brettanomyces, a wild yeast that creates funky, “barnyard” notes; or Lactobacillus and Pediococcus, bacterial strains that produce tart overtones. Now, some brewers are using wooden barrels to give these beasties a welcome home.

Through a 24-year brewing career, Gansberg says, “I got tired of the very hoppy beers that our area is producing, and I was looking to brew a beer that gave an intense sensory experience that was not from hops. The sour beers are definitely the opportunity.”

A Cascade barrel facility now in the planning stages is of a similar scale to those of other brewers known to explore “critter” beers, notably Vinnie Cilurzo of Russian River Brewing Co. (who coined the term) and Tomme Arthur of Port Brewing Co., both in California, and both known for artful combinations of unconventional microorganisms with distinctive, retired wooden wine barrels. But Gansberg stays clear of the earthy Brettanomyces wild yeast favored by some experimental brewers, and relies on the souring effects of Lactobacillus. His efforts were rewarded with two medals at the GABF.

Gansberg contrasts his brewing approach with Belgian native Bouckaert. “He’s producing according to true Belgian philosophy, using foeders [very large wooden vessels]. We’re doing our own thing, which is different. We’re using barrels with indigenous wood, bugs that are indigenous and certainly fruit that’s indigenous.”

Gansberg happily cross-fertilizes the bourbon barrel and wine barrel traditions: “Even our bourbon barrels are bug-influenced. We have an expanding stock of beers souring in bourbon barrels.” This will be a surprise to brewers who trust that the alcohol concentration in a former bourbon barrel makes an accidental invasion by “critters” unlikely, and blurs the judging category lines between the sweet barrel-aged beers and the barrel-aged, deliberately soured beers.

Barrel Unions

The conflation of the word “barrel” and “aged” is so maddeningly thorough that Matt Brynildson, head brewer at California’s Firestone Walker Brewing Co., isn’t sure if anyone understands that the brewery’s award-winning ales are the result of fermentation―not aging―in wood. It’s a process where the brewer employs the powerful flavor effects of wood early in the beer-making process, not during aging. As such, the effect is potent and swift.

Brynildson won’t say Firestone Walker is unique in fermenting in wood―though he’d like to: “A lot of these guys doing Belgian-style brewing may be doing some or all of their fermentation in oak, so I can’t say we’re the only American brewery doing primary fermentation in oak. But what I do say is that we’re one of only two breweries left in the world using a Union set.”

A “Union set” is a reference to the Burton Union fermentation system, now only used by the Marston’s brewery at the iconic source of British pale ale, Burton-on-Trent. The archaic approach to brewing was the one that inspired David Walker and Adam Firestone to create the patented Firestone Union fermentation system.

In both fermentation systems―the original Burton and Firestone―wooden vessels are linked together in a yoke of connected vessels. As fermentation proceeds, excess yeast and beer are pushed out of the barrel, up a swan’s neck connection (an air lock of sorts) and into a common trough. From there, the beer is channeled back into one of the barrels, mingling the beers somewhat―hence the “union” of the name, Brynildson guesses―and vigorous yeast can be harvested.

In the Marston’s brewery, every attempt is made to minimize the influence of wood on the flavor of Pedigree, the renowned beer brewed on this system. Coopers on the brewery staff repair and recondition old wooden tanks, to preserve the flavor neutrality achieved over long use. By contrast, Firestone Walker has harnessed the union system to take advantage of the unique flavors this “athletic fermentation” causes and add wood character to their beers.

“In our system, we’re looking for an oak effect,” explains Brynildson. “We’re selecting new American oak, and we’re having barrels built to our specifications to obtain oak flavor. American oak happens to be the less expensive medium to build barrels, but, more importantly, American oak has a little more aggressive attack when it comes to oak character.

“Among winemakers, French barrels are coveted and are considered to have a softer effect on the finished product. It’s a little like comparing noble hops versus American hops: French oak is though to have a more “noble” effect on the character. But we found that there are too many other flavors in our beer―the hops, the heavy malt character―the assertive attack of American oak works perfectly.”

The Firestone Union system consists of 40 oak barrels. Every week, a batch of the brewery’s Double Barrel Ale is brewed on the Union system. Each week, a new, properly toasted oak barrel is rotated into the system, and the oldest barrel is rotated out. Even with that moderate amount of oak influence―the output from 40 barrels, from brand new to 10 months in age, are blended together―the influence of new oak at the lively fermentation state is so dominant that all the brewery’s flagship beers are blends of oaked and stainless-steel fermented beers―except in the brewery’s taproom, where an 100-percent oak-fermented Double Barrel Ale is always available.

A Celebration of Barrels

“A barrel is its own little ecosystem,” observes Jeff Sparrow. The Chicago-based brewer and author helps to organize the annual Festival of Wood and Barrel-Aged Beer, hosted by the Illinois Craft Brewers Guild, and now in its seventh year.

“Is it a new barrel, where you need to be very careful of the strong wood character? Is it a used barrel, what was in it before, what’s going to grow in it now depending on its history and what you do to it next?” he asks.

Over the years, Sparrow has watched brewers who are intrigued with the influence of wood on beer move away from barrel alternatives―toasted oak chips, spirals, oak “beans” soaked in bourbon―to employ true barrels.

“I think there’s the coolness factor,” he explains. “You walk into Russian River, and Vinnie has his barrels on prominent display. Pete [Crowley, Rock Bottom’s Chicago brewer] has them stuck downstairs, Goose Island has barrels in whatever spare corner they can find. If people see a beer with wood chips floating in it, well … but when you see a barrel, it attracts so much more attention.”

Over and above the impression a rack of barrels makes on a visitor, there are chemical interactions going on inside a barrel that no wooden substitute can duplicate―and no brewer can fully control.

The wooden walls of the barrel are slightly permeable, allowing the modulated exchange of gases with the world outside. And the size of the barrel governs the surface-to-air ratio, which sets the pace of chemical interactions within the barrel: smaller barrels are more active; reactions in larger barrels are slower and may lead to more flavor complexity. After experimenting with smaller barrels, New Belgium’s Peter Bouckaert has converted the brewery’s barrel program largely to huge foeders, where microorganisms can work at a more leisurely pace.

With the return of wood to the brewing process, the brewer is incorporating yet another variable―and a less predictable one, at that―to the brewing regime. Not surprisingly, given that every barrel has its own history (its cask character), a new skill is required in the brewery: that of artfully blending the products of different barrels to obtain the desired balance of flavors in the finished beer. The job of blending is a long tradition among lambic and sour ale brewers in Belgium. It will no doubt become a specialization on the American craft brewing scene if the infatuation with barrels continues to grow.

Are there “new” frontiers in the old craft of barrel-influenced beer? Other species of wood have been tapped for flavor: Hitachino Nest Japanese Classic Ale is aged in cedar casks, borrowing from the sake tradition; and Dogfish Head Craft Brewery has constructed huge tanks from palo santo, an aromatic hardwood from Paraguay.

The permutations are endless: delicate beers soured in chardonnay barrels; fruited porters aged in bourbon barrels; barley wines seasoned in former sherry casks―all relying on the talents of the brewer and subject to the mysteries of a wooden barrel. Who ever dreamt so many new possibilities could flow from such an old source?