It is called Yowza! and for the last 13 years it has lived inside a small keg not far from wherever Bob Kunz is brewing. It started off as a homebrewing experiment as Kunz would take yeast dregs from bottles of beer that he had enjoyed – mostly Belgian in origin – and would propagate the microbes to brew beer of his own.
Over time new strains were added to the mixture, nicknamed Yowza! accentuating attributes that Kunz, now the brewer and owner of Highland Park Brewing in Los Angeles, found pleasing. Ambient yeast also settled into the slurry over time and soon the combination became a certified house culture, specific to the brewery and nearly impossible to replicate.
“It is our history and environment in microbiology form,” says Kunz.
Terroir is something difficult to define in beer. Because ingredients like grain and hops come from different places around the globe, and yeast can be ordered from a catalogue, water is usually the most local product that goes into a batch of beer.
However, yeast lives in the air and changes from location to location, so brewers that have been pushing the envelope with wild or sour beers have been drawn to cultivating their own yeasts that is not only specific to a place, but also identifiable through flavor. It is like tasting a brewery’s DNA.
Every brewery that chooses to cultivate yeasts to create a specific flavor profile is working towards a common goal but is also proud to be different. Of the roughly 8,000 breweries currently operating in the United States many will talk of a sour or wild program, but the majority are using yeast pitches, including strains of Brettanomyces, that can be ordered through yeast providers.
Unique to a Brewery
“Brewers have access to all of the same clean and catalogued strains,” says Jeff Mello, the owner of Bootleg Biology, a yeast lab in Nashville, Tennessee. “A house culture is a magical thing of value that no one else can have. It’s unique to them and cannot be recreated by someone else.”
Mello has received samples of house cultures from breweries from around the country and keeps them safely stored should a brewery ever need a fresh pitch, especially if the current generation of yeast has changed to a place that no longer resembles its old self.
When brewers talk of house cultures, it is hard not to bring up the Lambic makers of Belgium. Among the most celebrated beer styles, the lambics made by breweries like Drie Fonteinen and Cantillon have flavors that are distinctly theirs thanks to microbes that have developed over the decades and live in the eves and other surfaces of the brewery and that inoculate wort to begin fermentation.
In late 2014 Jean Van Roy, the owner of Cantillon, told me that as his brewery had grown, he had taken on new warehouse space where barrels would be sent to age before being packaged and release to the public. He was so bent on giving those barrels that same ambiance as the brewery location that he had been spraying the walls with his beers to introduce the house yeast to the structure.
Unique house cultures can start with another brewer’s yeast, like taking samples from a bottle, or can be pulled from the air around the brewery or a specific location, or even from plants in specific places. From there they are nurtured and changed and cultivated.
Tasting a House Culture
Some cultures have higher acidity than others with a citrus aroma, while some have a funky, earthy, aromas from Lactobacillus. Brettanomyces is also often present with any number of characterists from leather and pepper, to stone fruits.
While the intention is to make sure a house culture imparts flavors and aromas that will be appealing to customers, they are developed to first be pleasing to the brewers that have nurtured them. Once that is achieved brewers are eager to share.
“I’ve had several people, who are big sour beer fans, says they can tell when they are drinking our beer blind that it’s ours,” says Levi Fried, co-owner of Long Beach Beer Lab in California. They brewery uses sourdough yeast from the bakery his wife and co-owner Harmony Sage, hand mixes each day.
“This is truly unique to us and only we can make this beer,” he says. “It’s an extension of ourselves.” Among the pronounced flavors his house yeast produces is an aged sherry note.
A brewery is not limited to just one unique house culture.
Brewery History in Yeast
Jeremy Inzer, the head brewer at Fonta Flora Brewery in North Carolina says the brewery is operating three separate strains right now, two which are banked at Bootleg Biology for safe keeping. The first, “O.G.” was created by brewery owner Todd Boera who pulled yeast samples from other brewery’s bottles back when he was a homebrewer. Another is called “Dandy” after microbes were stripped off of dandelions and cultivated. The third and most recent came from a coolship beer the brewery made on its farm in Nebo, N.C.
“It has this light fruity note like peach and mango,” he says. “It’s all yeast derived, and we’ve even thought that sometimes the flavors were too pronounced so we had to up the hop dosage a bit to keep it at bay.”
Unlike yeast from a catalogue which, if used correctly and in a recipe made the same way batch over bath, will always produce the same results, there is always a bit of uncertainty to using a house culture.
Mello compares to taming a wild animal.
“You’re never going to fully control it, and that’s the thrill of house a house culture, there’s a variability and you also know that you won’t have one hundred percent repeatability.”
This article originally appeared on ProBrewer.com in January 2022. All About Beer’s parent company has a partnership with ProBrewer.com to create original content for that website. New articles appear twice each week and subsequently are reposted on AllAboutBeer.com.