Yeast Doesn’t Fly and Your Sourdough Probably Isn’t That Special
What we’ve learned so far in the home baking era
Sara May threw away her Covid-era sourdough starter on July 7. She had named it Dave Startley, after the The War On Drugs bassist Dave Hartley, but May, a hospitality professional and writer, neglected him for a few weeks during a move from Philadelphia to Ithaca, New York. Dave’s surface turned black. She cried when he hit the bottom of the trash can.
Only a few months into a sourdough craze that left grocery store shelves naked of flour, interest in homemade, naturally leavened bread appears to be waning. But a monthslong food media blitz espousing the ancient practice of starter cultivation was enough to cement some dubious notions and outright fallacies about naturally leavened bread.
A monthslong food media blitz espousing the ancient practice of starter cultivation was enough to cement some dubious notions and outright fallacies about naturally leavened bread.
Sourdough starter is a functioning ecosystem of yeast, bacteria, flour, and water. And while it’s clear how the last two elements enter that ecosystem, internet how-tos often misleadingly instruct bakers on ways to capture wild yeast as it floats through the air.
“It just doesn’t work that way. Yeast cannot fly. They’re too big,” said Douda Bensasson, an ecological genomicist and assistant professor of plant biology at the University of Georgia. “There’s a certain critical size that a microbe needs to be to float, and yeast are not below that critical size.”
That’s all to say, absent an insect flying into a starter, it’s the baker — and not some chance encounter with a yeasty breeze — who introduces yeast strains to their sourdough culture.
Yeast survives in and on plants and animals everywhere on the planet — on our hands, on fruits and vegetables, in the guts of insects that pollinate crops, on wheat stalks and in the bags of flour that they yield.