As the sun rises over the towering red pines of Chippewa National Forest, bugs and bees buzz - scouring the nearly 700,000 acres of protected land for fruits and flowers to feast upon. Wild strawberries, blueberries, raspberries, blackberries, and cranberries all thrive here. This morning though, they aren't alone, as I too forage for an organism that's been used by humans to make beer for over 9,000 years - yeast.
Before you read on (and if you're 21 or older) crack open a nice beer. The etymology of that beverage you're holding stems from a process that man accidentally discovered 9,000 years ago - when a bowl of hawthorn berries, honey, and rice was left out to spoil. After a few weeks, the liquid turned into something sweet and pungent and, when drank, made your head spin. Spontaneous fermentation occurred. This is the basic premise for how we at Portage collect and use wild yeast in our fermentation process.
Since our start in 2017, we've collected and propagated only two cultures of wild yeast, due to the fact that these organisms have an ability to clone and grow their cells exponentially (sometimes 10x in ideal conditions). The process for collection involves a summer afternoon outside. By bike or hike, we pack up sanitized centrifuge tubes, in search of anything that attracts yeast or bugs. Among the best hosts - ripe berries and flowers with a noticeable white powder on them. Deciduous trees also attract yeast as their light bark, receiving intense ultraviolet damage from the sun, have evolved to attract yeast as a natural sunscreen.
Once harvested, we head back to Portage and cook up a light batch of wort (sugary liquid) for the yeast to eat, reproduce, and ferment from. Those samples are then set aside in a warm place, allowing the cells to work for two weeks. From there, we take gravity readings to tell us the weight of the liquid (pure alcohol and water have gravities of 1.000, sugar does not). If sugar content in the sample hasn't decreased, then fermentation didn't occur. If sugar content does drop to near zero however, then we have fermentation, pasteurization, alcohol, and something worth smelling and tasting. If the sample passes these checks and is free of any noticeable bacteria or molds, we propagate the strains in Erlenmeyer flasks for commercial propagation.
Our use of wild yeast enables us to make beers that are more unique to their natural and local settings. Minnesota is very suitable for this style of brewing, as you generally want to pull microbes from clean, natural areas (like a forest) - Chippewa National Forest is rich with healthy hosts to attract wild yeast. Due to this fact, there are limited places in the United States where this style of brewing can occur. Many breweries who want to experiment with wild yeast end up purchasing materials from afar, rather than harvesting and growing their own cultures, locally.
Tinkering with wild yeast has been a passion of mine for years now - after spending time at Wild Mind Artisan Ales in Minneapolis, which specializes in wild and wood aged ferments, as well as homebrewing with it for years. Today, 80% of our hop forward beers call for wild yeast. From the 4.5% ABV Minna Wild Table Beer, to the 6.5% ABV Idlewild Wild IPA, to the 8.5% ABV Juicetree Wild Double IPA. Notes left behind in these beers from yeast include tart berry, wildflower, and honey.
I recommend any homebrewer to try this. If anything, it will get you outside, exploring our vast forested lands, while opening up your mind to a curiosity for experimentation in beer. There are also many history lessons to learn from wild fermentation. If you are curious to try, check out our blog at www.portagebeer.com for an article we wrote on Wild Yeast Foraging. There, you'll find a simple way to test these methods, and even produce your very own homebrew using wild yeast.