The goal of the Puratos Sourdough Library is to save the variety of sourdough starters, which are called unique “leavening agents.” (Puratos)

The goal of the Puratos Sourdough Library is to save the variety of sourdough starters, which are called unique “leavening agents.” (Puratos)

Founder Karl De Smedt is a baker-turned-librarian. (Puratos)

Founder Karl De Smedt is a baker-turned-librarian. (Puratos)

The library began with 43 starters, but now it has at least 125. (Puratos)

The library began with 43 starters, but now it has at least 125. (Puratos)

Mr. De Smedt holds petri dishes that have bacteria cultures from different sourdough starters. (Puratos)

Mr. De Smedt holds petri dishes that have bacteria cultures from different sourdough starters. (Puratos)

The gases that the bacteria and yeast let off created the bubbles in this finished sourdough loaf and caused it to rise. (Puratos)

The gases that the bacteria and yeast let off created the bubbles in this finished sourdough loaf and caused it to rise. (Puratos)

Sourdough Library

Posted: July 1, 2020

No need to bring your card to this library in St. Vith, Belgium. To use its contents, you don’t have to read. But you do have to know how to bake . . . and how to keep a pet alive.

Sourdough is fermented dough made with wild yeast and bacteria. It’s how leavened (rising) bread got started. The first bakers couldn’t just pick up a tiny yeast packet at the store. They had to capture wild yeast from the air with sourdough starters. These mixtures of water and flour wake up yeast—a teeny, God-created living thing—and make it useful to people. Many bakers still choose to “make” their own yeast this way. Countless kinds of bacteria live in different places in the world, so every sourdough starter is unique to its area. Each has its own smell and imparts its own tangy flavor to bread.

Baker-turned-librarian Karl De Smedt traveled the world. He watched bakers in China steam sourdough buns. In Mexico, he followed bakers crafting birote bread using sourdough made with eggs and lime. In Japan, he learned how bakers add sourdough to Sakura Anpan—cherry blossom buns filled with sweet bean paste. From each baker, he borrowed a bit of starter.

Now Mr. De Smedt has at least 125 starters in his collection. His finds wait in jars in cabinets at the bakery supply company Puratos. Each cabinet stays at 39 degrees—just right for keeping the sleeping yeast alive. Mr. De Smedt adds fresh flour to each starter every two months. He uses the same flours that the bakers first made the starters with. Now if bakers ever lose their original starters, they have backups in the Puratos library.