I’m down on my hands and knees, with my face inches from a fermenter’s open valve. Why we pitch five-gallon buckets full of goopy sourdough starter into our beer tanks has become an existential question that haunts me as I stare at a cake of flour that refuses to be dislodged. I will ultimately have to dismantle the bottom of the fermenter to get it out.
After five years of brewing with sourdough, you’d think I would have learned my lesson. I’ve ended many long days cursing those flour cakes—beer on me, my face, and the floor. But sourdough is intoxicating. We can’t resist it. The wild yeasts and bacteria in our starter make up the house fermentation culture at our southern Illinois brewery, Scratch.
The first time we brewed with sourdough, we made a sour wheat beer in the style of Berliner Weisse—a tart German wheat beer typically brewed with both Saccharomyces cerevisiae, the workhorse ale yeast that ferments most beer (and bread), and souring Lactobacillus.
We knew that a sourdough starter usually contains both, so we thought ours might work in place of mail-order laboratory cultures. After a quick week of fermentation, we were delighted to discover a light and refreshing tartness, with notes of green apple and pear. It was lovely—and we were lucky. There is no book on brewing with sourdough, so we have learned to work with our culture through experimentation, including how to keep souring bacteria and other bugs in check using the antimicrobial powers of hops, allowing us to make saison-style farmhouse beers without funk.
There’s no question that our sourdough culture is distinctively our own. We grew it in our kitchen, and now we only feed it flour grown and milled in Illinois. But does it make our beers taste distinctively Midwestern? I’m not so sure. I’m always surprised by how much they can taste like classic hefeweizens or saisons, demonstrating the ancient link between beer and bread. Long before brewers understood yeast or bacteria, they were harnessing the same wild organisms that leaven bread to turn sugary wort into alcoholic beer, from Mesopotamia to northern Europe.
There’s no question that our sourdough culture is distinctively our own. We grew it in our kitchen, and now we only feed it flour grown and milled in Illinois. But does it make our beers taste distinctively Midwestern?
Before attempting any new sourdough project, make sure your starter is vigorous and healthy. My number-one piece of advice to brewers exploring sourdough is that if a starter doesn’t make good bread, it won’t make good beer. Baking is the best way of knowing if your culture is happy. If you’re making thin, dense loaves, your culture is probably sick. All it needs is a little revitalization. Give it a hearty feed and let it do its thing at room temperature for twenty-four hours. Sourdough cultures are incredibly resilient—ideal companions for our time.
To build a culture for a five-gallon batch of beer, mix 15 grams of starter with 20 grams of water and 20 grams of flour. Leave the mixture in a sealed container for twenty-four hours at room temperature before pitching. For a saison-like result, use enough hops to reach at least 22 IBUs and pitch your culture around 70°F. For a sour beer, do not hop the wort and pitch around 85°F. Allow the beer to ferment at ambient temperatures until fermentation is complete.
For everyone else
I don’t expect that most readers with healthy sourdough starters will go out and buy homebrewing equipment. There are other ways to make delicious drinks with the wild yeasts and bacteria that you’ve collected. Try using your starter to ferment kombucha or jun, or any other drink with a sugary, fermentation-ready base that benefits from some acidity. (Just remember that cultures will continue to work until they consume all fermentable sugars, creating alcohol and carbon dioxide in amounts that can detonate a sealed container. Loosen your lids or cover your jars with cloth.)
Russian kvass is a small beer traditionally made with rye bread that is a fantastic introduction to brewing at home, requiring no special equipment. Slice your bread (any flavorful loaf will work for this recipe), then toast the slices until golden and steep them in hot water overnight. The next day, strain off the liquid, add sugar if desired for more alcohol and body, and pitch your culture—about 10-15 grams per gallon. Discard the bread. Ferment your kvass for twenty-four hours or up to a week, depending on how alcoholic and dry you want the final product to be, and enjoy it cold, by itself or infused with mint, for a refreshing warm-weather drink that you can make entirely from your sourdough leftovers.