How colonies of bacteria and yeast create bubbly, tangy sourdough starters from just a simple mixture of bread and water is one of the most fascinating mysteries in food science. What are these microscopic organisms? What makes the colonies grow the way they do?
These are the driving questions behind the Sourdough Project, based in the lab of Rob Dunn, an applied ecology professor at N.C. State. The research project started in 2016 with a call for home bakers to send samples of their starters to the lab, and bakers responded from across the globe. Researchers on the project’s team extracted the DNA from these samples to determine the species in each starter. The group then analyzed how the location, gender of the baker, type of flour, and other external factors contributed to that profile.
These factors only explained 13 percent of the variation in species, so the Benjamin Wolfe Lab at Tufts University conducted more tests to find out what behaviors in the yeast and bacteria make them more or less prevalent.
To date, the project has received samples from 567 starters (the oldest dates to the 1730s) from 17 countries (the farthest: Australia). The most dominant yeast species has been Saccharomyces cerevisiae (strains 1 and 2), the same yeast sold in grocery stores, which was dominant in 460 samples. The most dominant bacteria species has been Lactobacillus brevis (strain 1), often found in milk products, which was dominant in 123 samples. Different species of the Lactobacillus genus were found in at least 230 other samples.
Each new discovery gives rise to many more questions, says researcher Erin McKenney. “Sourdough is really exciting,” she says. “This is a mystery that nobody has really solved yet.”
Related: See “Everything You Know About Sourdough Is Wrong, Says Master Baker Lionel Vatinet.” Contact us at food@indyweek.com.
This was a cool article. As a trained microbiologist I loved learning about this study. Has Rob Dunn’s laboratory taken swab samples of the hands of the baker’s that submitted their bread starters? A baker I interviewed once said there was a study done where several bakers made the same exact bread, in the same location, with the same ingredients. And it was noticed that the flavor was affected by the resident flora of each baker. I hope my question doesn’t gross out anyone.