Culturing for Science Class: Sourdough

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Last fall, my son asked me if we could make homemade sourdough soft pretzels.  Since I gave my sourdough starter away a few years ago, I suggested that we try an experiment– creating our own. I have a recipe for starter in my favorite cookbook; here are the instructions we followed:

  1. In a large bowl, dissolve 1 package of active dry yeast (not quick rise) in a ½ cup of non-chlorinated or filtered warm water.
  2. Stir in 2 cups of warm water, 2 cups of all-purpose flour and 1 tablespoon of sugar or honey.
  3. Beat until smooth.
  4. Transfer to a large, wide-mouthed mason jar and cover with a tea towel. Secure the covering with a rubber band.

Each day for ten days, we fed the starter with flour and water.  We measured 1/2 a cup of starter, discarding the rest, and fed the reserved starter ½ a cup of flour and ½ a cup of warm water, stirring with a wooden spoon and re-covering with the tea towel to prevent any fruit flies from getting to it.  Do not keep your starter in a metal container or stir it with a metal spoon, as the metal can sometimes react with the starter and change the taste of it.

We recorded any observations that the children made; for example, air bubbles after being fed, or the sourdough smell beginning to develop.  We marked the level on the side of the jar with masking tape, labeled “Day 1,” “Day 2,” etc. to show how the starter grew after being fed.



We found resources online to explain how the sourdough starter works.  I explained to my children, this is how all bread was made before the invention of quick rise yeast, and how the fermentation process makes the wheat easier to digest.  We also discovered a web page with instructions on how to participate in a more detailed sourdough science project, compares different types of flours, and includes a data sheet to download and fill in.  We attempted to create another starter with gluten-free flour to compare to our regular starter, but it did not do as well as the starter made from wheat.

After ten days, we put a cap on the mason jar and moved it to the refrigerator.  Once a week, we take it out and feed it as we did when we were making it, along with a ½ a teaspoon of sugar.  We give it a few hours to “eat” and then return it to the refrigerator.  We baked our soft pretzels using the starter we created and my son was very pleased with them!

This was an interesting project and we enjoyed doing it. I encourage you to try it with your children if you’ve ever wanted to learn more about baking with sourdough.

“A little leaven leaveneth the whole lump.” – Galatians 5:9


Heather Eberlin is a married mother of four children, ranging in age from seven to twenty-six. She is currently homeschooling her two youngest children and has felt called to share her journey in order to encourage others. She is an amateur gardener who is amazed at the things that God’s creation reveals when you take the time to pay attention to it. You can follow her at Musings from My Garden or download her free Homeschool Organizational Forms here.


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"Train up a child in the way he should go and when he is old, he will not depart from it" (Proverbs 22:6).