What Does Your Sourdough Starter Smell Like? Science Wants to Know

A citizen science project aims to chart the microbial diversity present in starters all over the world

Rye and wheat sourdough starters
As many home bakers who have only recently taken up sourdough making have found out, some starters are, well, non-starters. Photo by: Natasha Breen/REDA&CO/Universal Images Group via Getty Images

Bread is big in the time of COVID-19. Home bakers are firing up their ovens in droves and for many there is no substitute for sourdough, with its airy bounce, complex flavors and its beguiling, biologically active catalyst called starter.

As its name suggests, starter is what makes sourdough go. It’s a mixture of flour and water that becomes something bubbling and primordial when it is colonized by whatever wild yeasts and bacteria happen to be in the area. The goopy, living substance leavens the dough, helping the bread rise when baked.

People are serious about their starter, which needs to be kept alive with regular feedings. Belgium has a sourdough library to showcase starters from around the world, and Sweden has a hotel that offer to keep starters cozy while you're away. Miners in the California Gold Rush cuddled it to keep it warm.

But as many home bakers who have only recently taken up the mantle have found out, some starters are, well, non-starters. The resulting breads don’t rise and the first instinct may be to throw out the starter along with the fossilized loaf and begin again.

But those looking to find a way for their delinquent starters to contribute to society can upload the microbial mix’s vitals to the Wild Sourdough Project from the Public Science Lab at North Carolina State University, report Brianna Scott and Christopher Intagliata for NPR. The lab is searching far and wide to learn more about the microbes that make up winning and losing starters, and they’re asking the public to contribute.

"I'm really hoping that some people can give us information about the starters that do fail because we don't hear about that enough, and we definitely don't hear about failures enough in science in general," Lauren Nichols, an ecologist who manages the lab's Wild Sourdough Project, tells NPR.

The citizen science project asks participants to follow a ten-day plan to try to get their starter going. Whether or not things take off biologically speaking, the scientists then want folks to fill out a questionnaire about their starter. After answering basics such as what type or types of flour are being used and where it’s being grown, the project wants to know how high the starter rises and what it smells like.

If you’re sniffing and sniffing without quite being able to put your finger on the smell tickling your nostrils the site offers a handy aroma wheel to help out with suggestions ranging from the appetizing (Are those notes of apple and beer?) to the repulsive (“My starter smells like vomit inside an animal stable.”).

This may seem like relatively simple home science, but it provides researchers with a jumping off point for further inquiry.

“So now we can ask very specific questions about how does the grain type and how does where you live in the world geography affected the leavening or the rise, and how much do those same factors influence aroma?” says Erin McKenney in conversation with CBC’s Matt Galloway. “Once we see some extremes … we can start to ask what creates those really unusual starters with really unusual aromas or leavening properties.”

Apart from its scientific purpose, the project also aims to bring people together.

“We want to do more than science here, we want to build community,” says Rob Dunn, one of the scientists involved in project in a statement. “Our hope is that in making starters as part of a common project that people can come together, virtually, around food, science, heritage and flavor.”

The data on homemade starters will build on the researchers’ existing work with the Global Sourdough Project, which used genetic analysis to identify the microbes present in starters from around the world. The project received 1,000 responses to their survey as well as 571 starter samples from 17 countries, reported Stephanie Parker of Civil Eats last year.

And to those feeling intimidated by sourdough’s fermented grandeur, McKenney offers some words of encouragement: “Instead of feeling like there's no single right way or there's no direction,” she tells CBC, “think of it as artistic license to really learn the specific nature of your particular microbial garden and how it behaves in your home and your hands.”

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