The first time Michael Crane, a homebrewer who since helped found Crane Brewing in Kansas City, collected yeast in the wild, he started by setting a large bucket under a friend’s pear tree. The culture he discovered fermented beer that tasted like a saison. When Christian DeBenedetti went looking for a wild strain that might become the house yeast for Wolves and People Farmhouse Brewery in Oregon, he started with what he found on a plum from perhaps the oldest tree on the farm where the brewery is located. The yeast turned out to be well suited for producing saisons.
Across the country, Jasper Akerboom harvested wild yeast from five sites in Virginia and one in New York. Akerboom oversees quality control at Lost Rhino Brewing and is a partner in Bright Yeast Labs. He estimates that he has isolated about 100 strains and that they all share what he describes as “outspoken character,” what others might call “saison-like.” “I have not found anything that is really mild,” he says. Instead, the strains tend to be “wild,” estery, and often need to ferment at higher temperatures. Most of them do not flocculate very well.
Notice something similar? American brewers interested in making beers that fit under the rather broad umbrella of saison don’t necessarily need to look toward Wallonia. The answer may be in their own backyards. But just to be clear, this is not to suggest that somebody will discover the long-lost twin for Saison Dupont yeast floating in the northern Montana air any time soon. Nor does it imply wrangling a strain suitable to brew with is as easy as finding one that will ferment wort.
There are several questions brewers need to ask first.
What is wild yeast?
Quite often when brewers, and their fans, talk about “wild yeast,” they mean a mixed culture that also contains Brettanomyces and bacteria such as Pediococus and Lactobacillus. However, that isn’t the wild yeast we’re talking about here. The most straightforward definition of what we mean by wild yeast comes from Jeff Mello, who operates Bootleg Biology and launched the Local Yeast Project in 2014 with a goal to collect a culture from all 43,000 ZIP codes. Mello says wild is “a culture that has never been part of an intentional fermentation. As soon as you do that, then to me, while you may not have changed the genetics, you have selected a strain and excluded others. You are in the process of domesticating it.”
Thus, a single “pure” Saccharomyces cerevisiae (ale yeast) collected in the wild can produce the “wild” saison character Akerboom is talking about. One reason is that any yeast collected in the wild will be phenolic off-flavor positive (POF+). “I have no doubt [about that],” says Karen Fortmann, senior research scientist at White Labs. Those phenolics are not appropriate in most beers but contribute the spicy, sometimes clovy, character found in strains used to brew German Weiss beers and many Belgian beers. They are essential in saison.
How do you collect wild yeast?
Mello’s Backyard Yeast Wrangling Tool Kit is sold in the CBB&B online store and at homebrew shops across the country, but he also provides instructions for collecting wild yeast at the Bootleg Biology website. What Crane did illustrates how simple it can be. He sanitized a large bucket, added about a quart of water, covered the bucket with a paint strainer and set it under the pear tree. He added what found its way into the bucket to low-gravity wort, attached an airlock to the beaker, and waited. Within two days it was bubbling. Inside of a week there was a thin layer of yeast on the bottom, gravity had dropped to 1.010, and he knew he had something that would metabolize wort into alcohol. He chilled the beaker, decanted the liquid, and added fresh wort. He did this repeatedly for more than a month, until the slurry was thick enough to ferment 5 gallons (19 liters) of wort into beer.
An adventurous brewer may choose to isolate a single colony. Mello has information about how to create agar plates, streak the plates, and pick a single colony, as do Chris White and Jamil Zainasheff in Yeast: The Practical Guide to Beer Fermentation. It isn’t hard, but they include a warning to be taken seriously. “Use caution when tasting any native fermentation, especially if it does not smell like beer,” White and Zainasheff write. “You might want to avoid tasting any spontaneous fermentation, waiting until you have isolated the yeast and grown up a pure culture from it.”
Akerboom concurs. Last fall, his presentation titled “Isolating interesting wild Saccharomyces yeast strains for brewing applications” was awarded best paper at the Master Brewers Association of the Americas Annual Conference. In the paper, he basically outlines backyard wrangling on a larger scale. Before any sensory evaluation, he screens the sample to ensure that the organism captured is Saccharomyces that will ferment wort. “Everything after that is the smell and taste test,” he says. Another option is to send samples to a laboratory to have single strains isolated.
Do you want to tame wild yeast?
This is the $64,000 question. Small breweries are increasingly interested in finding their own proprietary yeast. Akerboom says, “When you want to work with local yeast, you need to start from scratch. You have a better understanding of what the yeast is, what it wants to do. It is good to see how it behaves in its own environment.”
But he cautions, “I think a lot of strains in brewing have been domesticated, very domesticated.” Strains collected in the outdoors are acclimated to that environment. “They always going to be a little wild,” he says.
Quite obviously, wild yeasts are attractive when brewing saisons because they are wild, so a brewer who wants to maintain that character should take that into account. Unfortunately, there is no real way to select for the wild character the way a brewer can select for flocculation and fermentation.
And selecting for such characteristics as flocculation and fermentation could affect the wild character because strains used in brewing may adapt or change each time they are reused due to selective pressure and repitching methods. They are also organisms that reproduce quickly and so may change quickly. Akerboom emphasizes that newly collected single strains are likely to drift strongly when they are initially repitched. “More than an English yeast. That organism has been in that environment [wort] for a long time.”
It might not always be the case that a collected strain loses its wild character. Akerboom says it depends on what the brewer selects for (on purpose or inadvertently). He says that “evolution” of flavor/aroma (“wild character”) might go more slowly than the evolution of other characteristics, but “it does not mean it does not take place.”
American yeast, American beer?
DeBenedetti sent the culture he collected off the plum to White Labs, where they isolated a single strain he named Sebastian, after Sebastian Brutscher, a Bavarian immigrant who in the nineteenth century began growing crops on the land on which Wolves and People is located.
“We are finding [Sebastian] is very diverse,” DeBenedetti says. “There are a lot of esters, pear, marmalade, and nice spicy notes. Sometimes clove.” After fifteen generations, “we feel like we’re just getting to know it. It’s evolving. One thing I like is it is a snapshot. Give it a different environment and it changes.”
Wolves and People is located on farmland outside Portland where DeBenedetti grew up, but he is not shy about taking inspiration from beers brewed in Belgium. Sebastian will continue to be the primary strain, but the brewery will also use it in tandem with yeast found elsewhere on the farm, such as from rose hips and from hazelnut tree flower blossoms. “And we’ve collected the dregs from great beers we admire,” he says. They’ve also developed a house sour culture. “Our goal is to be all wild, but there are certain beer styles that don’t lend themselves to the profile [Sebastian produces],” he says.
DeBenedetti recognizes that consumers mentally link “farmhouse brewery” and “Belgian beer” but that romance and reality must intersect at a certain point. “We are not historical reenactors,” he says. “We have a lab. We do cell counts. We want to make the most authentic beer we can, from the farm and from this location. A pure expression of place.”
It turns out that’s naturally a bit wild.
The Yeast Family Tree
Research teams from White Labs and a Belgian genetics laboratory only recently created the first genetic family tree for brewing yeasts by sequencing the DNA of more than 240 strains. The tree makes it easy to visualize possible relationships among varieties considered British or American, for instance, and in turn the relationship between them and strains found in the wild. (White Labs Founder Chris White talked about “Unlocking the Genetic Code of Brewing Strains” at the National Homebrewers Conference in June 2016, and it was one of the most revealing of dozens of presentations.)
From sanitation and inoculation to propagation and fermentation, Craft Beer & Brewing Magazine®’s online class Care and Feeding of Yeast has everything you need to build a healthy population of yeast and make the best beer possible.