The DMNS and Denver Beer Co conduct a wild brewing experiment with City Park yeast
City Park has always been a little wild.
DMNS health sciences curator and chair Nicole Garneau.
Denver's largest green space touches on more than a dozen urban neighborhoods and is home to lions, elephants, bald eagles and just about every form of recreation. So it's no surprise that there are also wild yeasts floating in the air around the park and settling on everything from the trees and grass to the sidewalks, buildings and even the wolf-pack sculpture outside the Denver Museum of Nature & Science.
And that statue is one of five places in the park where museum curator Nicole Garneau, along with Denver Beer Co owners Patrick Crawford and Charlie Berger, collected yeast samples last week in order to conduct a novel brewing experiment: They hope to use the yeast to ferment a beer that could be served at the museum's next Science on Tap event.
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"Worst case is: we make a beer, and it tastes like crap," says Garneau, a fun-loving geneticist -- and beer drinker -- who runs the Health Sciences Department at DMNS and does public outreach with students and visitors to the museum.
Garneau will test yeast taken from five objects in City Park, including rose bushes.
Actually, that's one of the best-case scenarios. The worst-case scenario is that the yeast includes some form of bacteria that makes everyone sick. To avoid that, Garneau, who has a Ph.D. in microbiology, is conducting a few experiments in the museum's lab.
After collecting samples of yeast -- which are naturally occurring living organisms -- from the sculpture, some rose petals, Ponderosa pine tree bark, Blue Spruce needles and a couple of bugs (yes, bugs), the team transferred them to a nutrient solution and then spread the mixture onto five different Petri dishes where they could grow some more. From these, individual colonies of yeast were isolated and streaked onto a final plate.
On Tuesday, Garneau isolated one yeast colony from each dish and mixed it with sterile, unfermented beer that Denver Beer Co had brought to the museum for the experiment.
Unfermented beer was inoculated with five different yeast colonies.
Unfermented beer, known as "wort," consists of malted barley that has been boiled to extract the sugar, along with hops and sometimes other ingredients. To make it alcoholic, brewers add yeast, which essentially eats the sugar and ferments the wort.
Most of the yeast strains that brewers use have been cultivated (or selected and maintained by yeast companies), and their flavor profiles are well known.
If some of the wild yeasts Garneau has in her lab -- or even just one -- are able to ferment the beer, it means they don't have bacteria in them and are safe to drink.
Once that is completed, however, she'll have to test the isolated yeast colony to make sure that it can live in alcohol. To do that, she sought the advice of another local yeast expert, Chad Yakobson, who runs the Crooked Stave brewery in Denver, which specializes in fermenting beers with proprietary wild yeast strains.
Garneau asks Denver Beer Co's Patrick Crawford a last-minute beery question.
"He suggested we use vodka because it's high in alcohol, so if it can grow in vodka, it can grow in beer," Garneau says.
If that works, then Garneau, Crawford and Berger will need to hustle, dumping the winning yeast in more nutrient solution so that it can propagate enough of itself to be put into a small, five-gallon batch of beer that Denver Beer Co can brew on July 8 and serve at the Science on Tap event on July 22, alongside the same beer -- a traditional pale ale -- that has been fermented with two well-known brewers yeast strains.
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