About 87 miles southeast of Brussels, the residents of a living library are fermenting away. Some 125 mason jars of bubbling sourdough starters—mixtures of flour, water and microbes—sit in the refrigerated cabinets of the Puratos Sourdough Library in St. Vith, Belgium. Each jar is numbered, and many are named.
Sourdough librarian Karl De Smedt, a confectioner and baker by training, has traveled the world to build the library’s collection. He oversaw the venue’s opening in 2013 and has gathered up to a few dozen starters each year since. Visitors can learn more about De Smedt’s “quest for sourdough” by taking the library’s virtual tour.
“Finding sourdough is a bit of an adventure,” De Smedt told Roads and Kingdoms’ Rafael Tonon in 2018. “But it’s a way of helping to rescue these stories. After all, more than distinct flavors, aromas and biochemical characteristics, what we keep in each of these jars is nothing less than history.”
Belgium-based bakery supply company Puratos began collecting starters in 1989. As its reserve grew, reported Anne Ewbank for Atlas Obscura in 2018, De Smedt suggested creating a display space to house the unusual trove.
The virtual tour places viewers in a 360-degree version of the wood-paneled room. Its walls are lined with refrigerated cabinets kept at about 39 degrees Fahrenheit, and its ceiling looks like a forest canopy. De Smedt, standing in the middle of the room, is ready to give a short introduction, but visitors are also free to jump straight into the short videos documenting several starters’ stories.
Though the tour highlights just 12 starters, the library actually had 125 starters in storage at its most recent count, according to Franz Lidz of the New York Times. Per Roads and Kingdoms, the majority of starters are from Europe, particularly Italy, but the collection includes starters from the United States, Japan, Brazil and other international destinations, too.
Each year, De Smedt chooses a few starters to join the library. Selections are made based on the concoctions’ flour type, level of fame, unique origins and estimated age.
“Most importantly, the sourdough must come from a spontaneous fermentation, and not inoculated with a commercial starter culture,” De Smedt tells the New York Times.
Still, he says, while estimated age is a factor in choosing which starters join the library, the team has no way of knowing exactly how old samples are.
Adds De Smedt, “The microbial colonies of a starter can change entirely, depending on how it is fed and maintained. If someone insisted she had a 500-year-old sourdough, I’d have to believe her.”
Sourdough #39 is from Amfilochila, a small village in Greece where household starters are fed with holy water that has been ceremonially mixed with local basil. Sourdough #43, meanwhile, is from San Francisco, the source of America’s iconic sourdough, and Sourdough #64 is from northeastern China, where starters are used to make steamed buns.
Each sourdough starter is scientifically analyzed to determine its microbial makeup. According to Atlas Obscura, this research has turned up surprising connections, like a wild yeast present only in two starters from Switzerland and Mexico—a similarity De Smedt theorizes might be linked to the countries’ high altitude. Another pair of starters had matching lactobacilli, a naturally occurring bacteria needed to make sourdough. The starters’ only shared characteristic was the fact that they were created by women.
Once a starter has been entrusted to De Smedt and the Puratos Sourdough Library, the team follows a strict protocol designed to bring the sample to Belgium without contaminating it. Staff also ask starters’ owners to send a supply of ingredients, including the specific flour used, in order to maintain the specimens’ makeup.
The Belgian institution likens itself to preservation projects like Norway’s Svalbard Global Seed Vault, which safeguards crops.
“Sourdough is the soul of many bakeries,” says De Smedt to New York Times. “When bakers entrust you with their souls, you’d better take care to it.”