I admit, I’m behind the times. While my friends are attending increasingly popular beer festivals and visiting the growing number of micro-breweries around the world, I can’t tell the difference between a lager and a stout. This means that not only am I the worst person to send to the bar, I’ve also never given much thought to what it takes to brew a great beer.
Unlike me, John Sheppard is a beer expert. As a bioprocessing professor at North Carolina State University, Sheppard spends much of his time in his lab (which could easily be confused for a miniature brewery) studying how to best grow and control yeast—the fungi that convert sugar into alcohol. His current project, brewing with wild yeast, has brought him outside that controlled environment into a world he didn’t expect.
Typically, the yeasts used to brew beer are specifically selected from a small group of previously tested strains to protect the beer’s characteristics. In fact, Sheppard’s research usually centers on controlling yeast metabolism to achieve consistent performance of the essential ingredient. Sheppard says, “wild yeasts have always been considered a contaminant in brewing and you want to keep them out, because they create off-flavors.”
In 2014, the North Carolina Science Festival coincided with the World Beer Festival in Raleigh, North Carolina. That overlap prompted Jonathan Frederick, director of the science festival, to ask Sheppard about creating a special exhibit on the science of beer—specifically, on fermenting beer with wild, unknown yeasts. Frederick suggested that Sheppard reach out to Robert Dunn, a biological sciences professor at North Carolina State University, and the rest is history.
Just kidding, the rest included a lot of hard work and time spent finding wild and useful yeasts to develop new brews. Work in Dunn’s lab focuses on the ecology of small species, some of which carry yeast in and on their bodies, so they decided to try some pests. Along with post-doctoral researcher, Anne Madden, the team isolated a yeast carried by wasps and found that it was suitable to ferment and brew.
The team first had to remove the yeast from the wasp. To do this, the wasps had to be killed, ground down, and then placed in a nutrient solution—where the yeast and bacteria grew. The scientists isolated and removed the yeast, tested it to be sure it was safe, and used it to create beer.
Sheppard tested the wild yeast under normal brewing conditions and discovered that they “don’t particularly like very cold temperatures.” So he adjusted the fermentation conditions a bit, raising the temperature slightly above average, but still within normal range. To create beer, yeast must ferment a brewer’s wort, or the liquid sugar extracted when a grain is milled, mixed with water, and heated. Sheppard learned that this wild yeast could ferment the same brewer’s wort he uses for his standard beers.
Despite this success, Sheppard suspected the brew he developed from the wild yeast wouldn’t taste great. “Actually the opposite was true,” he says. The yeast not only produced ethanol, but also esters, which create a fruity flavor, and lactic acid, which produce a sour character. Sheppard says of the beer, “We got some really nice fruity, flowery esters that gave it a nice taste and aroma, combined with a moderate sourness.” After the success of the first beer, the team decided to try another—this time with yeast from bumblebees. It was also well received and Sheppard thought, “maybe we’ve hit on something here.”
Sheppard is not the only one experimenting with wild yeast. Owners of the Catillon Brewery in Anderlecht, Belgium have been brewing their beer with wild yeasts since 1900, using the extremely old lambic method—spontaneous fermentation and open exposure to wild yeasts and bacteria—which produces a very sour beer that is an acquired taste.
More recently, U.S. brewers are getting in on the wild yeast game. Allagash Brewing Company in Portland, Maine, Crooked Stave Artisan Beer Project in Fort Collins, Colorado, and Russian River Brewing Company in Santa Rosa, California all offer beers made from wild yeast.
The team at North Carolina State University is just starting out in the beer world. They have produced a small supply of beer for campus events, but they’re not quite ready to release the wasp beer yet. They are in the process of identifying and isolating more wild yeasts, mostly from other wasps and bees, and Sheppard sees a range of possibilities for their use. “The microbes that are currently used for food and beverage production are a relatively small percentage of the total possible microbes that could potentially be used,” says Sheppard. He thinks there’s a big opportunity for these undiscovered yeasts.
I’m looking forward to finally being the friend in the know and ordering everyone a round of bumblebee beer.
Lindsay Smith spends most of her time making her mother worry and planning her next snack. She’s an editorial assistant at National Geographic and tweets @lindsayn_smith.