All About Beer Magazine - Volume 32, Issue 2
May 1, 2011 By

The growing number of entries to sour beer categories 
suggests that brewers are onto something new. 
But the techniques they’re using, and the “bugs” they’re 
welcoming into their beers, have a long history.Sour is the new bitter!” trumpets a newspaper column. Yikes, that sounds like a hard sell. So hostility has replaced resentment?
No, not really. We’re in the world of specialty beer, where sour and bitter can be positive things. The headline refers literally to two basic human tastes and the possibility that a new flavor may be gaining ground with beer lovers.

In recent years, craft brewers have reveled in pushing the bounds of bitterness, challenging their thirsty fans with beers heaped with hops. Starting with India pale ales and their more aggressive younger siblings, imperial IPAs, the trend then spread into other categories, with pilsners, porters and barley wines jostling for bitter supremacy.

But craft brewers are a restless bunch. Lately, a growing number have looked to another element to balance beer’s basic sweetness: instead of bitter-sweet, these beers lean towards sweet-sour. And although the term “sour beer” sounds off-putting at first, there are some exciting flavors awaiting the adventurous drinker. Sour beers faithfully preserve a centuries-old legacy. And, to the delight of modern drinkers, today’s brewers are shaping old styles and techniques to produce an array of new possibilities.

Sour—And More

As we learned through the bitter era, bitterness in beer is not one-dimensional. It can come from a number of sources and be expressed in an array of intensities. Most obviously, hops add bitterness. But the hop variety, the amount used and the timing of its addition, as well as its combination with other varieties, can take a beer from lightly floral to teeth-peelingly harsh. And hops are not the only source of bitterness: Roasted grains, malted and unmalted, can add a burnt-toast astringency to a beer even when the presence of hops is negligible.

So it is with sourness. An assortment of bacteria can contribute sour tones to beer, with intensities that range from lightly tangy to puckering. Rogue yeast strains also contribute acidic notes, and all these organisms produce different effects depending on their succession in fermenting and aging beer. And fruits, spices and other unusual additions can contribute to a sour profile.

Lumping all these beers under the description “sour” runs the risk of emphasizing their most simplistic quality. Jeff Sparrow, the Chicago-based beer author of Wild Brews, originally titled his book Sour Beer. But as he explored the Belgian brewing traditions that have contributed so much to the topic, he changed his mind. “I always say that this beer isn’t sour—it’s wild. I say that because, if all a beer was, was sour, who’s going to like it? There’s so much more going on.”


That’s true, but “sour beer” is the term showing up in both headlines and competition categories, which makes “sour” hard to avoid as a leading descriptor.

But Sparrow is right, there is much more going on. In fact, there are three closely overlapping trends attracting attention in specialty brewing. Although all three can have a role in a single beer, they can also exist alone or in combination. It’s a useful exercise to tease them apart: You may discover you like one or two qualities, or you may embrace them all.

Sour Beer: Our tongues register sourness as one of the five basic tastes (sour, bitter, sweet, salty and umami). Taste buds can detect levels of acidity: basically, they measure the pH value. More sophisticated discrimination—does this taste tart? Is it lactic? Is it vinegary?—relies on the interaction of our senses of taste and smell.

The primary sources of acidity are the closely related bacteria Lactobacillus (the sour milk bacteria) and Pediococcus, which both produce lactic acid; and Acetobacter, the source of acetic acid, or vinegar. Lactic acid is a relatively simple flavor, with a sweet-sour quality; acetic acid is sharper. And both acids can interact with alcohol to form chemical compounds known as esters. When all these elements combine, they can produce great complexity in a beer.

Wild Yeast: Brewer’s yeast, Saccharomyces cerevisiae, was purified in the late 1800s, allowing brewers to exclude other yeasts they found undesirable. One particular genus of “wild yeast,” Brettanomyces (“Brett”) is considered a source of off-flavors in both beer and wine. Indeed, the common Brett descriptors—horse blanket, band-aid, barnyard, sweat—scarcely sound appetizing.

But fans of lambic, Belgium’s most ancient beer style, recognize these flavors and aromas as essential components of these complex beers. Other Belgian beer styles display lower but still important levels of Brett as part of their character. And now, a number of American craft brewers are infatuated with these wild yeasts whose presence once would have been considered an infection, and are learning to deploy them in their beers.

Brettanomyces also contributes some acidity to a beer, but that can be easily overwhelmed by other sources.

Wood or Barrel Aging: For centuries, brewers used wooden containers to ferment, age and store their beer. When an alternative presented itself, most brewers happily adopted materials that were easier to sanitize and more resistant to invasion by unwanted organisms.

But some brewing traditions clung to wood’s qualities. Wood is permeable to oxygen, which allows communities of organisms to live on and in its surface, where they contribute to beer character. If allowed to, Brettanomyces and other organisms will take up residence permanently in wooden barrels.

Wood has other qualities, too. Oak, the most common material for food-grade barrels, releases vanilla-like compounds into the barrel’s contents. Wine makers value different species and sources of oak for different wines, and distillers have learned to char the inside of a barrel to impart toasted and caramel notes to spirits. Brewers take advantage of both new and used barrels to give their beer added flavor.

Wood- or barrel-aging, then, can mean different things: It may be that the beer is affected by the flavors of the wood itself, or by previous liquids stored in the wood, or by microorganisms that colonize the barrel—or all three.

Putting the Pieces Back Together

Much of modern brewing relies upon culture yeast, purified single strains available thanks to the work of Danish scientist Emil Hansen, who propagated the first pure yeast at the Carlsberg labs in 1883 (goodbye, Brett); and on Louis Pasteur’s technique of pasteurization, which uses heat to kill bacteria in beer (goodbye, souring bacteria).

But if we step back to the days before Pasteur and Hansen, most beer must have combined—to some degree—the three elements above. Matured in wooden vessels, it was vulnerable to invasion by a range of microorganisms. Much of it must have been a little sour, and a little funky.

Yet there was good beer before the modern age of brewing: Beer was not a random, fermented slurry. Even if they didn’t know the microbiology involved, brewers learned to coax and manage fermentation and aging. They channeled the brewing process, even if they did not control it. And drinkers distinguished between sour/pleasant beer and sour/spoiled beer.

Randy Mosher, the writer and beer historian, cites old references to demonstrate that the difference. “The Egyptians had a little epithet, back 5,000 years or more, that said ‘May you have bread that doesn’t go stale and beer that doesn’t go sour,’” he says. “And if you look at English brewing books from the 18th century or so, there’s always a chapter on how to fix sour beer, even though they also valued a particular type of aged character they called ‘stale.’ That was valued, sour wasn’t. In looking back at that period, it isn’t clear exactly what they were talking about.”

Aged, or stale, beer was one of the components of porter, the style that evolved from the blended beers publicans dispensed in 18th-century London. Cheaper, fresh ale could be mixed to the drinker’s requirements with more a costly, stale beer, which no doubt exhibited a degree of bacterial sourness and some Brett. In fact, although Brettanomyces is largely associated today with Belgian brewing, it was first identified in a sample of English ale: The name means “British fungus.”

(The tradition of including a portion of aged beer in porter may—or may not—be maintained today in porter’s relative, Irish dry stout, a style that evolved from the strongest of the porters. Guinness, the most famous stout brand, has a recognizable sour note that is reputed to come from three or more percent of “vinegarized” beer from old wooden vats, blended into every fresh batch. Although Guinness does not discuss brewing details, if true, that would make this Irish dry stout the most widely consumed “sour beer” in the world.)

English porter brewers and their contemporaries appear to have perfected the controlled aging of a portion of beer in huge wooden casks, which was then blended with beers of different ages. Today, the only remnant of this technique in Britain is at the Green King Brewery at Bury St. Edmunds. Their Strong Suffolk Ale is a blend of a 12 percent alcohol, highly lactic ale matured in 100-barrel oaken vats with a younger, fresh beer.

This method is maintained today across the Channel in West Flanders, the home of sour red ale. Eugene Rodenbach, whose father founded the eponymous brewery famous for this style, studied brewing in England in the 1870s. According to Peter Bouckaert, now the brewmaster at Colorado’s New Belgium, but formerly employed at Rodenbach, “If you read what Eugene brought back to Rodenbach, it was the porter process.”

The English “porter process” may have influenced sour beer brewing in Belgium, but by the next century, Belgium would be the preserve of most, though not all, styles of deliberately soured beers.

Classic Sour Beer Styles

There are a handful of beer styles brewed today where sourness, with or without the influence of wild yeast and wood, is an expected and welcome part of the beer’s profile.

Lambic: These wild-fermented beers from the Pajottenland region southwest of Brussels are the oldest beer style still made. The brewing process is archaic: When the wort (the sweet liquid precursor of beer) is ready, it is exposed to the open air to be colonized by ambient wild yeast and bacteria. This sounds haphazard, but it is anything but­­— unable to control the organisms that settle in the beer, the lambic brewers instead manage the conditions in which the beer ferments and matures. According to Jeff Swallow, the airborne organisms probably aren’t sufficient to get fermentation going. The secret is to move the inoculated wort to barrels that contain reliable communities of organisms. After one to three years, a master blender combines lambics of various ages—a step that is repeated in many other wild and multi-organism beer styles—to create a final beverage that is layered, complex and challenging.

West Flanders Sour Red Ale: These brilliant, tart beers also rely on the perpetuation of bacterial colonies in wooden vessels to add lactic and acetic (vinegar) notes to the aging beer, as well as related esters. At renowned Rodenbach, brewmaster Rudi Ghequire defines the acidification of the beer as “a late Middle Ages conservation method” that prevented spoilage by pushing pH levels too low for dangerous bacteria to thrive, as older, more acidic beer was mixed with younger batches. Foeders, the giant oaken tuns where the beer matures, vary enough from one to another that several different foeders are tapped for the final blend.

East Flanders Brown Ale/Oud Bruin: In East Flanders, the region’s sour beer is based on a brown ale, with more caramel, toffee and dark fruit notes than the red beers of its western neighbor. The oud bruin (old brown) beers are matured in stainless steel, a more controllable medium than wood. One notable example of oud bruin, Liefmanns Goudenband, is an almost purely lactic beer, with little acetic or wild character. The final beer has a rich, malty character, almost sherry-like.

White Ale/Wit Beer: This spicy Belgian wheat ale was once one of many similar beers found across Belgium and into England. It teetered on the edge of extinction early in the 20th century, and was revived in large part by Pierre Celis, who brought the style to the United States. Randy Mosher recalls, “Pierre Celis was pretty generous with details about his beer, but I understand he had a locked room in the brewery in Texas where only he had the key, and he did some sort of lactic 
fermentation in there. It’s a minor detail, but it’s an important part of the overall flavor profile of those white beers to have a kind of a bright, palate-cleansing acidity that helps balance the creamy, milkshaky texture.”

Berlinner Weisse: Napoleon dubbed this cleanly acidic wheat beer “the Champagne of the North.” Mosher, again: “That’s a lactic fermentation. Historically, those beers were made from unboiled wort. If you’ve ever smelled spent grain or grain out in the field, that stuff has a huge amount of lactic and Pediococcus bacteria living on it naturally.” Other, rarer north German beers, such Lichtenhainer and Leipziger Gose, also display some lactic acidity, either from bacteria or from the acidification of the malted grain.

American Brewers Turn Sour

In the 1990s, a small number of American microbrewers turned away from the British traditions that had influenced many of their colleagues and founded companies based on Belgian-inspired brewing. Allagash in Maine led with its wit beer, while Brewery Ommegang’s abbey ale was modeled on the sweet, potent beer styles associated with monastic brewing. At New Belgium Brewing Co. in Colorado, the flagship Fat Tire, a spicy amber ale, supported a portfolio of similarly malt-forward beers. Initially, sour styles didn’t get a look-in.

A few U.S. breweries took a walk on the wild side. New Glarus’ Wisconsin Belgian Red, brewed with cherries, bested the Belgians at their own game in international competitions, but the beer attracted attention more as a breakout fruit beer (against a backdrop of indifferent raspberry wheats), rather than as a pioneering sour beer—which it was. Southampton Publick House experimented with sour styles, but in the main, these styles were one-offs made by brewpubs, and none seemed to reach the magical “tipping point.”

When Peter Bouckaert took a job at New Belgium after many years with Rodenbach, his first foray into sour beers came with “absolutely no plan around it.” An early attempt at an oud bruin was a failure. But in 1997 the brewery purchased a dozen small wine casks as an experiment.

In 1999, the brewery committed to a serious barrel-aging program, investing in large foeders, each with 50 to 100 or more times the capacity of a wine barrel.

The brewery created La Folie, a blended sour brown ale aged in French oak; one of the first beers of its sort brewed in the United States. It took a gold medal at the Great American Beer Festival in 2001.

In northern California, Vinnie Cilurzo, an innovator already credited with creating the first imperial IPA, began experimenting with unusual microorganisms—“critters,” he jokingly called them—and different base beers. In the barrel room at the Russian River brewpub in Santa Rosa, these beers aged in oak barrels that had housed particular wine varieties under the eyes of curious beer fans. In the heart of California wine country, Cilurzo’s wild beers played with flavor agents that frankly scared the neighbors.

Head Brewer Tomme Arthur, at Port Brewing Co.

Meanwhile in San Diego, Tomme Arthur offered occasional sour-wild beers to the customers at the Solana Beach Pizza Port, and took honors for Cuvèe de Tomme, a strong brown ale that combined sour cherries, wild yeast and bourbon-barrel aging.

Arthur also took up Peter Bouckaert’s suggestion to brew a 100 percent Brett beer: The seemingly contradictory “pure” strain wild brew proved illuminating. “It’s not nearly as sour as you might think it would be,” Arthur recalls. “Brettanomyces on its own produces a pleasant tart character that can easily be overwhelmed by other constituents of the beer. It was quite fruity, and the essence manifests itself in a sort of pineapple-tropical fruit character.”

A few years later, as the head brewer of Port Brewing Co., Arthur proclaimed his love of wild yeast in a sign over the brewhouse door, and launched an elaborate barrel program.

The trend gathered momentum. A quick survey of the changing list of beer categories at the Great American Beer Festival in the past decade tracks the evolving passions of American craft brewers. Through the 2000s, the number of Belgian-style categories expands; a separate sour beer category is added, then another; wood and barrel-aged categories appear, then multiply as entries grow; and distinctively American takes on sour, wood-aged, German and Belgian styles emerge.

Small breweries that staked their fortunes on these unusual beers have seen their bets pay off. Ron Jeffries, who founded Jolly Pumpkin Artisan Ales in a garage in Dexter, MI, ages all his bottle-conditioned beers in oak. He acknowledges the risk of being at the leading edge: “Selling all oak-aged sour beer when we opened was quite a bit tougher than it is now. One would be justified in saying it was quite tough, and calling us pretty silly to only brew sour beer. To this day we receive email: ‘Hey, did you know your beer is sour?  I think you have a problem.’  Not as many as when we opened, but we still do.”

Cascade Brewing Co. in Portland, OR, has been stunning consumers and beer judges with Northwestern sour beers, many flavored with local fruits, spices and flowers, nurtured in a barrel house that contains over 300 barrels. Brewer Ron Gansberg stays away from wild yeast, preferring lactic fermentation instead. Cascade acquires barrels not just from wine sources, but from spirits as well. The marriage of sour beer and bourbon-barrel aging has made his Bourbonic Plague a prize-winner.

At Upland Brewing Co. in Indiana, brewer Caleb Staton brews wild beers modeled on traditional Belgian lambic practices, but with an American accent. His fruited sour ales include kiwi and persimmon, a clear break with European tradition. He calls the sour beer market “a niche within a niche,” where “sourheads” are emerging alongside better-established “hopheads” among the enthusiasts.

Now, in a second decade, brewers are clearly intrigued by the possibilities of wild/sour/woody beers. The Festival of Wood and Barrel Aged Beer, hosted by the Illinois Craft Brewers Guild, held its eighth event in November of 2010, with 156 different beers for its guests. Among the more intriguing entries, “Wild Acidic Beer aged in old French oak wine barrel with Brettanomyces bruxellensis, Lactobacillus, Pediococcus” from A.C. Golden Brewing Co.—the experimental arm of MillerCoors. If it seems strange that Coors is dabbling in wild yeast, it is worth remembering that Blue Moon, based on a once-obscure Belgian wit beer, is the most successful specialty style to go mainstream.

Probably more significant for the craft beer scene, after this issue goes to press, Vinnie Cilurzo will be hosting a symposium at Russian River prior to the annual Craft Brewers’ Conference, which he describes as “an intense social gathering of brewers who are either making or interested in making sour/barrel beers.” He explains, “This is vital because if a consumer gets hold of a sour/barrel beer that is so far out there and potentially ‘off,’ it could affect the long-term decision he or she makes towards this style of beer, and this won’t help anyone. This is such a niche market that I don’t see any real reason to be secretive about what we do or our process.”

Two-hundred brewers have signed up for the symposium, and another 50 have had to be turned away. Some niche.

Peter Bouckaert rejects the idea that this is the next wave in so-called “extreme beer.” Instead, he makes it sound like a return to brewing’s organic roots. “I don’t think of this as extreme brewing,” he says. “To me, Budweiser is an extreme brew. Because, in nature there are a lot of stable, robust cultures that are a mixture of different yeasts and bacteria. There’s so much out there and what do we do with nature? We clean it up. To what? Sacchromyces cereviciae took over the beer landscape and made it very boring.”

Sour, wild, wood-aged beers are anything but boring. Their unpredictability can be unnerving. So many more of nature’s variables are at play during fermentation and maturation; the brewer is dealing with complex ecosystems, not a straightforward industrial processes. But beer lovers who embrace these new interpretations are finding flavors that stretch our modern definition of “beer”—and remind us of its origins.