A FEW MILES north of Portland, Maine, inside Allagash Brewing Company's gleaming fluorescent-lit beer factory, a heavy door leads into a climate-controlled room lined with barrels full of aging beer. Past those barrels, behind a second, smaller door, is one of craft brewing's most sacred spaces. In here, the thrumming industrial drone of bottling lines and keg washers fades away. Wooden casks stand silent sentry. Dust hangs heavy. Cobwebs lilt. The owner of Allagash, Rob Tod, sets a small green bottle of beer on an upturned cask. Its contents were aged in this very room. He pops the cork and pours a fragrant, foamy measure into a yellow plastic KOA coffee mug.
It's called Resurgam—Latin for “I shall rise again”—and it is the most remarkable beer I've ever tasted: vibrant, alive with sweet white-pear notes, a clean, tart razor's edge, and a subtle berry finish. It is at once fruity and earthy, rich and light, hazy and bright—strawberries in hay under a summer sun. Complex and graceful, Resurgam and the rare few beers like it represent a style of beer that's flatly, even belittlingly, called sour.
Behind the brewery, Allagash's brewmaster, Jason Perkins, leads me to a wooden shed. Inside, a shallow stainless-steel pool nearly fills a wood-paneled room. That pool is called a koelschip, and it's the key to Resurgam's complexity, the place where protobeer comes into contact with the horde of wild microbes that will ferment it into something special. “We don't use chemicals in here,” Perkins says, pointing out a filmy ring of grime around the tub. They clean with hot water, lest they interrupt the magic of the Maine microbes that make Allagash's sour beers its own.
The hut is a shrine to localism, its wood reclaimed from trees cut down when the brewery expanded, its windows from an old church in town, its door from a nearby salvage yard, and its dirt blown in from the forest outside. Perkins and the other Allagash brewers want to capture where they are: the crisp air, the faint sea breeze, the spirit of the Maine woods. “We model our brewing after lambic production,” Perkins says, referring to the famous sour beers of Belgium. “But we were curious: If we did the same thing in a different part of the world, what would happen?”
The answer was Allagash's line of sours. Launched in 2007, they were the first lambic-style brews made in the United States. They're available only at the brewery, and new batches sell out within days. It's a cult-like devotion common in the sour world. Online beer forums are drool-sodden with reviews of unusual, expensive bottles and poetic descriptions of flavors and aromas like dandelion, unripe pear, green pineapple, and even “liquid farmyard,” “rotten oak,” and “crap-stained muck-spreader.” (The more masochistic the tasting notes, the higher the price tag.) According to the mythology surrounding lambics, the particular combination of microbes that makes those flavors possible—various species of yeast and other microbes that show up almost accidentally during a brewing process known as spontaneous fermentation—exists only in a few locations on Earth: the bright, perpetually autumnal Maine woods, for example. But above all, the verdant cherry orchards of the Zenne River Valley, southwest of Brussels. (When the city's famed sour brewery Cantillon updated its 115-year-old brewhouse, it saved the old ceiling tiles, because the brewers hoped the critical microflora were contained therein.)
WILLIAM BOSTWICK
ABOUT
William Bostwick (@brewerstale) writes, bakes, and brews in San Francisco. Parts of this story appear in his book The Brewer’s Tale.
Call it microbial terroir. In winemaking, terroir refers to characteristic flavor that comes from where the grapes were grown and the wine was made. It is geography we can taste, whether it's the limestone-laden soil of the Champagne hills or the cherry-scented air on a spring day in Brussels. But if microbial terroir defines a sour beer's destiny, then understanding the biology of those microorganisms should be enough to let anyone manufacture as good a sour as Allagash or Cantillon. I don't live in the woods—I make beer on a chipped four-burner, five stories above San Francisco's Mission District. To purists, making a sour here would be like growing world-class Pinot in Times Square. The best way to find out if they're right: brew one myself.
BEFORE LOUIS PASTEUR uncovered the microbial basics of fermentation, the creation of beer seemed magical. For centuries, the microflora that turn vegetables to pickles, milk to yogurt, and grain porridge to beer—each process a kind of fermentation—were revered and unknown. Brewing was the domain of ritual and prayer. An early term for yeast, the then-unknown stuff that turned boiled grain into beer, was Goddesgoode—“God is good.” Today, of course, foodies know they have Lactobacillus, lactic-acid-making bacteria, to thank for pickles and yogurt, and a species of yeast called Saccharomyces cerevisiae to credit for bread and beer. But over a century ago brewers figured out that another genus of yeast, Brettanomyces—a sign of spoilage in most beers—was responsible in part for the weird flavors in lambics.
Fermenting yeasts produce more than just ethanol and carbon dioxide. They make flavorful, aromatic molecules: acids and esters. But which ones make which ones? In the past the shortcut explanation was terroir—something about the location, the specific microorganisms native to a place. Even today no one has a better answer. “We know what the acids and esters are, and how they're made,” says Jim Withee, founder and CEO of GigaYeast, a beer yeast manufacturer in Belmont, California. “But not why—and most curiously, not what evolutionary and environmental advantage they have. Why has that genetic code adapted to that environment?”
If you believe the hype, the best wild beermaking microbes come from the golden fields of Belgium's Pajottenland—more specifically, the tiny town of Lembeek, an early medieval brewing hub. But until 2012 no one really knew which microbes. That's when a team of researchers applied modern genetic sequencing technologies to sour beers. They found quite a community and laid bare some of the secrets of the fabled lambic.
The first organisms to take root during fermentation, the researchers learned, are bad ones indeed: bacteria like Enterobacter cloacae (responsible for urinary tract infections) and Klebsiella pneumoniae (yes, like a respiratory infection). In theory they're dangerous. But they're only temporary tenants, doing their work and then dying before they can do any harm to fetishistic fans of sours. Among other compounds, they produce acetic acid—vinegar—which gives some lambics a pleasant tang. More than that, though, they break down polysaccharide sugars—those made of multiple subunits—into the smaller sugar molecules that yeast can digest.
That's what makes it possible for S. cerevisiae to move in. The carbon dioxide it makes bubbles away through the barrel staves; the ethanol stays. But yeast cells are smoky little engines that give off clouds of fragrant and flavorful molecules too. An enzyme in S. cerevisiae called alcohol acetyl transferase, for example, connects the alcohol with a molecule called acetyl-CoA to make banana-y isoamyl acetate and pearlike ethyl acetate.
When the yeast die, they make way for the next wave of organisms. Pediococcus—another genus of bacteria—teams up with Brettanomyces to eat the complex, longer sugar molecules that S. cerevisiae miss. Pediococcus produces lactic acid, lambic's dominant flavor note, but can also emit funkier flavors such as buttery diacetyl. And besides forming a goopy film on top called a pellicle, which allows it to access oxygen while sealing off the beer below, Brettanomyces also makes stuff like caprylic acid (goat smell) and ethyl lactate (horse-blanket smell). They're what make a farmhouse beer taste like a farm.
6 GREAT SOUR BEERS
If you’re looking to try a sour beer but don’t want to hazard making your own, a few craft breweries have you covered. Here are some of my favorites.
—W.B.
Allagash Coolship Resurgam
Hometown: Portland, Maine
Alcohol by volume: 6.0–7.0 percent
Flavor notes: Sparkling bright, impossibly fresh, flaky strawberry shortcake spritzed with rose water
Russian River Beatification
Hometown: Santa Rosa, California
ABV: 5.5 percent
Flavor notes: Sharp and prickling, opens with zested grapefruit, closes with a slaty, tannic snap
Jolly Pumpkin Artisan Ales Bam Bière
Hometown: Dexter, Michigan
ABV: 4.5 percent
Flavor notes: Light, crisp, and crackling as sunburned straw, a twist of lemon, pure farmyard refreshment
Sam Adams KMF Grand Cru
Hometown: Boston, Massachusetts
ABV: 6.4 percent
Flavor notes: Dark and roasted, kissed with oak and basement-floor earth; sweet like sherry vinegar and chocolate sauce
Cantillon Rosé de Gambrinus
Hometown: Anderlecht, Belgium
ABV: 5.0 percent
Flavor notes: Rich umami bloom with a buried subtle sweetness; dried cherries in fragrant melted Camembert
Gueuze Tilquin à l’ancienne
Hometown: Bierghes, Belgium
ABV: 6.4 percent
Flavor notes: Fruit first, funk second; a nose of sweet peach rolled in muddy hay, tart and dry as white grape skins
THOSE BUGS ARE everywhere. But sticklers say that unless the microbes are Belgian, a sour beer is not a lambic. So to brew my first sour, I figured I'd better import the right critters. For that, I turned to White Labs, a San Diego-based company that cultivates and sells yeast. In a move unusual for a microbiology firm, the company also has a tasting room—dozens of beers identical except for the yeast. The idea is to show off the flavors brought by the yeast alone—from WLP530 Abbey Ale to WLP885 Zurich Lager. But with sour beers now such a prize, White Labs has begun culturing Belgian-style bacteria as well. “In Belgium, their cultures are unique,” says Neva Parker, head of the lab. “What we do is try to re-create that.”
I went with White Labs Belgian Sour Mix 1. Parker told me it was a mishmash of Saccharomyces, Lactobacillus, and a wet-hay-scented kind of Brettanomyces bruxellensis common around the famous Cantillon brewery in Brussels.
I steeped cracked grain in a soup pot on my stove, boiling the result with a handful of crushed, pelletized hops—the preservative flowers add some complementary bitterness and keep the beer safe from truly poisonous bacterial infection. Then I chilled this wort on a 5-pound bag of ice in my sink, siphoned it into an empty cider jug, and upended the little vial of grayish slurry from White Labs. After about a day it started bubbling. (God is good!) Then nothing. I waited. A thin film began to slick its surface, sea-monkey-like flecks dove and rose in the hazy brew. I waited. And waited. And then plum forgot about it. After a year in my pantry, all the gunk had settled in a layer of gray-white sediment—dead cells that brewers call trub—and the beer cleared. I ventured a sip.
It was terrible. This was liquid fire—it actually hurt to drink. The sourness didn't blossom in layers of fruit and herbs, didn't ripple into lingering furrows of flavor—it stabbed.
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