Starters: Fermenting With Finger Yeast

My friend Wayne and his daughters Nico and Charlie recently made sourdough bread with homemade starters containing wild yeasts and bacteria.

Join Our Community of Science Lovers!

This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American


My friend Wayne and his daughters Nico and Charlie recently made sourdough bread with homemade starters containing wild yeasts and bacteria. They started with just flour and water, capturing microbes from the air that start chewing up the flour, making the bubbles and flavors that give the bread its texture and its kick. I love to see kids excited about microbes and I really love that they jump-started their fermentations with what they call "finger yeast," microbes from their fingers that got into their starters as they were making it and giving it a personalized flavor! Here's a great video of the girls talking about their experiences with baking and fermentation:

And here's more on the process and recipe from Wayne's blog:


On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.


Our own approach mixes as it departs from them all. We’re totally into starters and soakers and long fermentations and low kneading and hearty country loaves, but we’re hardcore about ingredients: we’re using 100% whole wheat flour (a lot of so-called whole wheat loaves are actually 70/30 or 50/50, with plenty of refined white flour to up the gluten ratio to better trap air and make the bread bubbly & springy); we’re also making “lean” breads (as opposed to “enhanced” with fats or sweeteners) — just flour + water + microbes + salt. It’s a challenge — for many, it’s long been a holy grail — but it feels elemental. And rewarding. Even when a loaf comes out flat, it still has amazing depth of flavor.

After mixing up their own soakers (water + flour, to help soften the bran and begin enzymatic processes) and starters (essentially, 60 grams of their cultures + 200g flour + 150g water) the night before, and letting them each go to work for 12 hours, they woke up and mixed their final doughs the next morning. I baked the loaves for the girls while they were at school, scoring each one with a first initial, and they came out just lovely — and were even tastier than they were beautiful...

We’re looking forward to future experiments with microbes — maybe future videos too. It’s been fun to learn about all this stuff together, and we hope some people might want to copy our experiments and share theirs with us. We’ll do our best to keep you posted on future things a-brewin’.

Make sure to check out the rest of the post for more photos and insights into fermentation. I can't wait for future experiments!

Christina Agapakis is a biologist, designer, and writer with an ecological and evolutionary approach to synthetic biology and biological engineering. Her PhD thesis projects at the Harvard Medical School include design of metabolic pathways in bacteria for hydrogen fuel production, personalized genetic engineering of plants, engineered photosynthetic endosymbiosis, and cheese smell-omics. With Oscillator and Icosahedron Labs she works towards envisioning the future of biological technologies and synthetic biology design.

More by Christina Agapakis

It’s Time to Stand Up for Science

If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.

I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.

If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.

In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.

There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.

Thank you,

David M. Ewalt, Editor in Chief, Scientific American

Subscribe