Join West Wyandotte Library Associate Emily as she dives into the world of fermented foods. Over the next few weeks, she will be sharing what she has learned about this fascinating type of food.

What is Sourdough?

At its core, sourdough is a type of fermentation that occurs by creating a wild yeast culture. This culture can be used to make breads and other baked goods.

To paraphrase from Living Bread, sourdough cultures form by producing wild yeast, which lives in flour and the air. Wild yeast is present in most places as microscopic, non-filamentous fungi. In other words, wild yeast is a type of fungus that does not have thread-like structures. (Leader, 173).

When water hydrates flour, it triggers enzymes in the dough that work to break down the flour’s starches into simple sugars. Wild yeast then feeds off these sugars, producing gas (carbon dioxide and ethanol alcohol), which causes the mixture to bubble and rise.

What puts the SOUR in Sourdough?

“Sourdough gets its name from the acids that build up during fermentation. Acid is not produced by yeast, but rather by different bacteria (mainly lactobacilli) that exist in the environment alongside yeast and feed off the sugars in the dough.”  (Leader, 173).

To put it simply, the distinct sour taste and aroma of sourdough is a direct result of bacteria found in the air.

Does Sourdough change based on the Environment?

There is truly no such thing as “San Francisco” Sourdough (or any other specific location, for that matter). As explained in Living Bread, sourdough is unique to each location and each baker:

 “Professor DeVuyst discovered that different areas of the world do have varying yeast and naturally occurring lactobacilli dominate in their respective cultures. However, once you take the culture out of its original environment, there is no guarantee that the original strains will continue to be the dominant forces within the sourdough” (Leader, 174).

In Living Bread, the author shares a story of receiving a specific sourdough culture:

 “I told him [DeVuyst] by the time I took some of my friend Steven Sullivan’s sourdough from his San Francisco bakery to mine, the bread always tasted more like the loaves I have always made than like Steve’s” (Leader, 174).

To put it another way, your own microbiota in your environment will create a sourdough loaf unique to your location and conditions within your kitchen. What a fun way to make your own signature breads!

Is Sourdough Good for you?

The easy answer to this question: Yes! Sourdough is full of “healthy” bacteria like lactobacilli. While the bacteria is cooked out during the baking process, the breakdown before baking still helps break down components in the sourdough, making it easier for people to digest. This is why people with celiac disease can often consume sourdough breads.

“Commercial breads can often be difficult for individuals to digest because it contains phytic acid” (Leader, 175). Scientists believe that digesting this commercial yeast is the cause of stomach pain. This acid also contributes to the body by preventing the body from absorbing nutrients that are supposed to make whole grain bread healthier.

Understand the Basics of Sourdough? Learn how to create your own Sourdough Culture!

Further Readings on Hoopla


  • Leader, Daniel. “Sourdough.” Living Bread: Tradition and Innovation in Artisan Bread Making, Avery, 2019, p.173.