Belgium Is Home to the World’s Only Sourdough Library

Though we usually think of libraries as a place that shelters books, some of humanity's most valuable items are a little more ephemeral. Consider the Svalbard global seed vault, which protects the world's crops against disasters, or the Ice Memory project in Antarctica, which is preserving ice cores from endangered glaciers in the face of climate catastrophe. Consider, too, the Puratos World Heritage Sourdough Library in St. Vith, Belgium, which is safeguarding more than 100 bubbling bread starters, as Atlas Obscura reported.

Sourdough may be the world's original leavened loaf. Though today most bakers use commercial yeasts, for thousands of years people relied on starters nourished by wild yeasts and local bacteria, which fermented over a period of days to produce a living, breathing blob. Bakers would spoon out a little at a time to add to new mixtures of flour and water before shaping their loaves; mothers would pass on the blobs to daughters beginning new families; immigrants and travelers would pack the starters to bake bread in new lands. Today, the sourdough starters in kitchens around the world represent a legacy of baking history, microbial diversity, and mouthwatering flavor.

The Belgian bakery supply company Puratos has been collecting sourdough starters since 1989, when they began with a venerable San Francisco sample. Part of the Puratos Center for Bread Flavor, the Sourdough Library—which opened in 2013—currently houses 108 starters from Italy, China, Hungary, Greece, Canada, and elsewhere, some of which date back hundreds of years. The collection is overseen by a genial man named Karl De Smedt, a "sourdough librarian" who travels the world to find new samples. De Smedt also makes sure the starters are "fed" every two months with flour provided by the original donors. "It's alive, it's like a pet," De Smedt told Atlas Obscura of the painstaking care they require.

De Smedt travels the world to find areas with robust sourdough traditions, like Canada's Yukon, where commercial yeast often hasn't survived in rugged conditions. After he airmails the starters in special kits back to Belgium, scientists analyze them to document their unique combinations of microorganisms. So far, more than 800 strains of yeast and bacteria have been found in the goo. The microorganism samples themselves are stored in a freezer at -112°F to preserve them, while the sourdough starters are kept in glass jars in the library at a more comfortable 39°F.

These days, sourdough is having a bit of a resurgence. Alongside the interest in all things handcrafted and artisanal, some have found that sourdough's long fermentation process produces a more digestible product for those with gluten sensitivity. The library's samples serve as backups for organizations and home cooks who might damage their own supply, as well as a fertile breeding ground (pun intended) for research and commercialization opportunities. Puratos also hosts an online sourdough database, where anyone can enter their recipe.

The library isn't open to the public, but Atlas Obscura notes that De Smedt is happy to show visitors around if they contact him via social media. And for those who can't make the trip to Belgium, an online version of the database provides detailed notes on the colors, textures, and flavors of more than 1400 starters. The library itself can also be explored via a series of videos here. You might just be inspired to rise to the occasion and bake your own loaf.