CINCINNATI -- While Greater Cincinnati is home to an up-and-coming local craft beer scene, one brewery is taking the word "local" to the next level.
Urban Artifact, located in a former church in Northside, is not only making local beer, but the brewers are doing so with local, wild-caught yeast and bacteria.
Chief of Brewing Operations Bret Kollmann Baker has been harvesting microorganisms all around the brewery, from its courtyard to its bell tower, to give Urban Artifact’s beer a truly unique flavor.
Harvesting Yeast
Yeast is a single-celled fungus that brewers use to ferment sugar into alcohol when making beer.
While most brewers purchase their yeast from labs, the microorganisms also live in the air, the soil, even on our skin.
“They are floating everywhere, all the time,” Baker said.
Although unsettling for germaphobes, the yeast go quietly about their business, living, reproducing and dying without most of us giving them much notice.
It is these wild strains of yeast that Baker enlists to make Urban Artifact’s beer, and he does so with the enthusiasm and gusto of a mad scientist.
Harvesting yeast is a simple enough process. Baker and his team simply set out a jar of wort, or unfermented beer, with a cheesecloth on top. After a few weeks, they check back in to see what has started to grow.
Wort, or unfermented beer, is used to collect wild yeast.
How do you tell if you’ve got a good strain of yeast for brewing?
Baker uses, what most would call, a smell test.
Bad yeast is pretty easy to identify. They usually give off smells of rotten food when they ferment sugar.
Good smells are usually crisp and dry, often with hints of fruit. Once a good strain of yeast is caught, a larger amount is grown in petri dishes. Then the yeast can then be used to make beer.
“It’s almost selective breeding,” Baker said. “You throw away cultures you don’t like until you get this weird, unique culture that’s semi-domesticated.”
Since each strain of yeast is slightly different, the flavors they bring to the beer through their unique metabolic processes also will be different.
This means that each batch of beer made will have its own individual flavor profile. In an age where reproducibility is a tenet of mass production, at Urban Artifact you’ll never have the same beer twice, something special that is not lost on the head brewer.
“It’s kind of a beautiful thing,” Baker said.
Natural selection at work
Wild-caught yeasts have been used in brewing for generations. These beers usually have an intentionally sour or tart taste, such a lambic, a gose or a Berliner Weisse.
This is done by adding a bacteria called lactobacillus during the brewing process. In addition to the yeast creating alcohol, the lactobacillus takes the sugar and converts it into lactic acid, giving the beer a sour taste, a similar process to how vinegar is made.
Urban Artifact uses separate tanks to make their beer sour. In these tanks, a bacteria called lactobacillus, caught from the brewery's bell tower, turns sugar into lactic acid.
However, sour beer is acidic. Most Urban Artifact beers have a pH of around 3.5, or about as tart as orange juice. Most yeast can’t live in such a low pH environment.
Urban Artifact’s brewers must culture their yeast in a way that makes the strain more acid-tolerant.
They begin by exposing the yeast to a slightly acidic solution. Though this might kill most of the culture, a few individual yeast cells whose genes allow them to withstand a lower pH survive. Those individuals reproduce and a new culture grows before it’s exposed to a stronger acid.
The process is repeated until the yeast can thrive in a sour beer. After a few weeks and a couple thousand generations, the brewers have developed yeast whose genes allow them to withstand the acidity.
Scientifically, tradition is for fools
Traditional sour beer is brewed with yeast and lactobacillus mixed together, creating whole microenvironments in which both microorganisms can thrive.
However, Urban Artifact has made use of a two-stage fermentation process.
First, brewers sour their unfermented beer by using their lactobacillus in a separate tank, then they pump the soured wort back into the brew kettle and add the hops and yeast.
While more established breweries don’t generally use this method, it’s made for some great beer. But tradition isn’t Urban Artifact’s, or Bret Kollmann Baker’s, style.
The brewery’s slogan is “wild culture”, referring both to the yeast used to make its beers and the eclectic musical acts which play nightly in the event space. It’s a mantra that has encouraged its brewers to experiment with their brewing.
Chris Anderson is a local science educator, aspiring science communicator, and founder of the blog scienceovereverything.com.
