Science with Mandy

Yum, sourdough bread! You might recognize it from the bakery section of your local supermarket or the menu of your favorite sandwich shop. Known for its sour and tangy taste, this bread is made (baked) possible (pun #1) through the action of various beneficial bacterial species, especially Lactobacillus, and yeast (1).

https://www.kingarthurbaking.com/recipes/rustic-sourdough-bread-recipe

So how do bacteria play a role in sourdough? Well, for starters (pun #2), if you mix flour and water and set it aside for a few days, you will have created your very own microbiome of bacteria and yeast – which come from the air, the flour, and other materials – that has begun to undergo fermentation (the anaerobic, or oxygen-less, breakdown of sugar [2]); this fermentation in what is called a sourdough starter (hence pun #2) generates lactic acid, acetic acid, and other materials, which gives the final bread product its signature taste (3,4). After the starter has formed, it is mixed with additional flour and water and baked to make the final sourdough bread product (3).

Do all sourdough breads taste identical? No! Many different factors contribute to the final taste of sourdough, including the specific microbial composition in the starter, the duration of the fermentation process, the relative amounts of fermentation products, and other things (4,5). Also, bakers will add other ingredients besides flour and water and make their own unique sourdough recipes. 

If you’re someone who likes to bake, or even someone who likes DIY science experiments, try making your own sourdough starter. At the very yeast (pun #3), check out some of the links listed below to learn more about this fascinating example of Beneficial Bacteria!

1. https://asm.org/articles/2020/june/the-sourdough-microbiome#:~:text=From%20these%20early%20studies%2C%20more,be%20living%20in%20sourdough%20starters.
2. https://www.britannica.com/science/fermentation 
3. https://www.britannica.com/topic/sourdough
4. https://www.kingarthurbaking.com/videos/baking-skills/where-does-sourdoughs-sour-flavor-come-from
5. https://www.kingarthurbaking.com/blog/2022/02/22/how-to-make-your-sourdough-bread-more-or-less-sour-part-1