“Before brewers became cognizant of microbiology and sanitation, I imagine there were a lot more sour beers,” says Mitch Steele, head brewer for Stone Brewing Co. “It’s not only bacteria but wild yeast as well that contributes a lot to the flavor and acidity of the beer. Belgian sours are done using primarily naturally occurring bacteria. German sour beer, or berliner weisse, is made by adding lactic-acid bacteria [Lactobacillus delbrückii].”

On Sunday, July 20, Stone will host its second annual Stone Sour Fest, during which people can taste an array of sour beers. At least 15 sour beers will be on tap, and over 30 will be available by bottle.

“Natural bacteria and yeast are used in a lot of applications in both the beer business and the wine business,” says Steele. “It’s probably how beer was discovered in the first place — malted barley got wet, and something in the air just started fermenting it. Up until a couple hundred years ago people didn’t understand it. It was Louis Pasteur in the mid-1800s who identified that yeast was a living organism. Carlsberg [the brewery J.C. Jacobsen founded in 1847 in Copenhagen, Denmark] was the first outfit to actually purify and isolate a single yeast strain and then culture that up for use in a brewery.”

Brettanomyces is a very aggressive yeast that will actually burrow down into wood,” says Mike Palmer, art director for Stone Brewing Co. “A lot of wine makers are superstitious about setting foot into a brewery that uses Brettanomyces because if they brought it back to the winery it could infect their entire operation — then there’s no way to get rid of the yeast except getting rid of all of their wood. In other words, starting over from scratch.”

When referring to this yeast, wine makers often use such negative terms as “fungal infection” or “spoilage organism.” Words used to describe its effect on the flavor of wine include “barnyardy” and “horse blanket.”

Unintentionally sour beers are spoiled beers, says Palmer. “There’s a small difference between sour and vinegar to some people.”

To brew sour beers alongside ales and stouts is a risky process. “If we were doing it here,” says Steele of brewing sour beers, “I would use separate hoses and separate pumps and use lots of hot water and chemicals like sanitizing acids. If you come across a beer that’s a pale ale or English or American style and it’s sour, you’ve got a problem.”

Steele says an unintentionally sour beer will have a “buttery character,” which comes from diacetyl, a by-product of fermentation.

“Sometimes, if you get a bacterial infection in a beer that’s not supposed to have one, you’ll get a lot of diacetyl. It smells like buttered popcorn.”

When making a sour beer, brewers will often compensate for the sourness by adding easily fermentable sugars.

“A sour beer will have different ingredients,” explains Steele. “Sugars in a beer that are not fermentable by brewer’s yeast are often fermentable by bacteria or wild yeast. You can get something really sour if you start off with a sweet beer.”

Fresh fruit (such as cherries, peaches, or raspberries) is added to the Belgian gueuze — a basic sour beer (like unflavored yogurt) known as lambic — to create sweet and sour beverages. The most well-known lambic producer is Lindemans, a Belgian-based brewery that has been producing lambic beer since 1811. Lambics are brewed in oak barrels and aged for up to two years before bottling. As has been the practice in Brussels and neighboring villages for hundreds of years, Belgian beers are “spontaneously fermented,” which means wild yeast and other cultures enter the barrels of wort (the beer mixture before fermentation) through open factory windows. According to one account of this process, “The fermenting rooms are dark and filled with cobwebs, and brewers dare not clean their brewing cellars for fear of losing the natural yeasts.”

Because of the laborious method of producing sour beers, they tend to cost more than other beer.

“Probably about double the cost,” says Steele. Though their popularity is on the rise and touted as the hot new trend by a handful of beer bloggers, sour beers aren’t for everyone. “I like hoppy beers,” says Steele. “Hops are used for bitterness and flavor, with citrusy, floral, and spicy-type aromas. Lambics and other sours typically have minimal hopping. If somebody’s looking for a traditional beer flavor, they’re not going to get it from sour beer.”

Sour beer, Steele explains, has both yeasty and bacterial characters. “First off, you get that intense lactic sourness that makes you pucker up. You get some esters, or fruity characters — maybe some banana or some kind of tropical fruit. We call it ‘the funk.’”

— Barbarella

Stone Sour Fest 2008
Sunday, July 20
11 a.m. to 9 p.m.
Stone Brewing World Bistro and Gardens
1999 Citracado Parkway
Cost: $30 Sour Pass for ten tasting tickets and commemorative glass
Info: 760-471-4999 or www.stonebrew.com/calendar

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