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A three-year-old bottle of Allagash Ghoulschip, brewed with pumpkin, toasted pumpkin seeds and molasses, and spontaneously fermented in the brewery's Koelschip.


Sour success: Allagash Brewery imports the Belgian art of spontaneous fermentation

by Will Grunewald
Nov 07, 2012


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Will Grunewald / MEDILL

Hot wort for a new batch of Ghoulschip is pumped into the Allagash Koelschip, where it will cool overnight and absorb yeast and bacteria for barrel fermentation that will last two to three years.

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Will Grunewald / MEDILL

Brewmaster Jason Perkins looks inside the Koelschip room as steam from the hot wort wafts out.  Brewery staff enjoyed a few bottles of 2009 Ghoulschip to mark the brewing of the 2012 ale that celebrates Halloween.

Funky, sour beer might surprise unfamiliar taste buds, but funk and sourness are exactly what brewmaster Jason Perkins set out to achieve with a series of spontaneously fermented ales at Allagash Brewery in Portland, Maine.

If Brettanomyces, lactic acid bacteria, and a variable mix of other microbes sound like the makings of a chemistry experiment, that’s pretty much what Allagash’s “Coolship” series of beers began as.

“There was definitely a good chance it wouldn’t work,” Perkins said. “And if that were the case, it would have been a lot of time and money spent on a project for nothing.”

Five years later, Perkins’ experimental brew has become a popular item among beer aficionados. Other Allagash ales are common in upscale Chicago stores and bars, but demand for Coolship beers has so outstripped supply that fans of the brewery will have to trek to Portland if they want a bottle. Past releases of 400-500 bottles have sold out within 48 hours.

Belgian brewhouses such as Cantillon and 3 Fonteinen have been making spontaneously fermented Lambic beer for more than a century, but their brew processes weren’t replicated by a U.S. brewery until 2007 when Allagash began its Coolship project. If the beer hadn’t turned out, it wouldn’t have surprised many in the beer world.

“There was some conventional wisdom that the only place you can make these beers is in Brussels or greater Brussels” because of the particular geography and temperate climate, Perkins said. “We were trying to see if spontaneous fermentation could occur here in Maine.”

So last week, when Allagash staff could mark the brewing of this year’s Halloween “Ghoulschip” ale by opening a few bottles from the Ghoulschip batch of three years prior, it spoke to the now-established consistency and success of the project.

In a usual brew process, brewers ferment wort – the hot liquid extract of fermentable sugars from malted grains – with a controlled yeast strain in order to achieve consistent quality. Any accidental contact with a wild yeast strain could ruin the beer. In spontaneous fermentation, though, the wort cools overnight in a shallow tub called a Koelschip (hence Coolship at Allagash), where it absorbs fermenting microbes from the environment.

Tradition suggested that the area around Brussels in the Senne River Valley uniquely comprised a geography and climate suitable for the wild yeast and bacteria that give Lambics their sought-after flavor profile.

Despite the conventional wisdom, “We had hunches that it would work here,” Perkins said. “We knew that there were Brettanomyces in our environment because we had discovered some just naturally occurring in our area. We knew that our weather profile at certain times of years was similar to the area around Brussels.”

And when food microbiologist Nick Bokulich learned of Allagash’s experimental endeavor, he saw an opportunity to scientifically test the idea that spontaneous fermentation is bounded by geography. From 2009-2011, Bokulich, of the University of California at Davis, used lab analysis of Coolship samples to determine the yeast and bacteria composition of each. Composition turned out to trump geography.

Bokulich found considerable similarities between Belgian Lambics and Allagash’s Lambic-style ales. Many of the same major types of microbes – Brettanomyces and lactic acid bacteria – are found in both, but many of the exact strains are different, which didn’t come as a surprise to Perkins, who reminds that the goal of the Coolship project isn’t to imitate the Belgian brewers’ products.

“We’re not trying to make their beer and we want to make sure they know that,” he said.

The Coolship project was designed to produce innovative beer, and beyond that to find out whether spontaneous fermentation could yield results on both sides of the Atlantic.

Bokulich said the success of Allagash’s Coolship experiment discredits the notion that terrain and climate determine the outcome of spontaneous fermentation. Factors such as temperature and the natural microbial population of an area still matter, but, “It’s really the brewery environment that enriches these Brettanomyces and lactic acid bacteria. You find the same sorts of stuff in breweries worldwide” – on the surfaces of barrels and brewing equipment, and floating around on particulate matter in the air.

From the regular brewing equipment to the separate shed that houses the Koelschip, the entire brewery environment influences the outcome of spontaneous fermentation. “There’s really no such thing as ‘spontaneous’ beer,” Perkins said. “It’s not like you could put a bucket of wort out in the parking lot and let it do its thing.”

But just because Allagash has shown that they can accomplish a spontaneous fermentation doesn’t mean that they’ve mastered the natural processes in play. Sometimes the beer simply doesn’t turn out right.

“We definitely lose barrels – barrels that just aren’t good quality,” Perkins said. Like most traditional Lambics, Allagash’s Coolship ales are blends of different aged batches. Especially early on in the project, losing barrels made it difficult to achieve the right blends. After five years of production, the brewery has enough batches under its belt to compensate for the occasional bad barrel. “Now, we can be picky,” Perkins said.

The Coolship project began as an experiment in chemistry and ecology. Since then, thanks to accumulated experience and accumulated barrels, the consistency of the product continues to improve. Still, the outcome of this experiment – with random, wild strains of yeast and bacteria in play – will never be 100 percent predictability. Balancing the right blends of barrels goes beyond any objective science.

“That’s really the brewer’s art,” said Bokulich.