We predict that the one loaf with extra yeast added in will make the sourdough rise higher than the one without extra yeast added in. I perdict that the one with more yeast will be more dense.

We researched what is sourdough, what is sourdough starter, and what is yeast. we used the following sites culturedfood life.com , foodbod.com, and red star yeast.com.

We measured the same amount of ingredients for the sourdough. We baked the sourdough in the same oven. We let them rest for the same amount of time. The thing we changed was the second loaf had a 1/8 teaspoon of commercial yeast added.

• weigh the sourdough starter to 90 g
• add 385g of room temp water
• in a different bowl weigh 12g of sea salt
• add 520 of un bleached flour to salt and mix
• add wet ingredients to the dry
• stir until flour is combined and creates shaggy dough
• cover with damp towel and rest for 15 minutes
• after that do set of 4 stretches and folds. lift one edge of dough and fold toward centre. turn bowl 1/4 turn and repeat
• let rest for 15 minutes covered
• do another set of 4 stretches and folds
• after that set sourdough in glass bowl
• put damp kitchen towel over glass bowl and sit it on a counter over night for 10.5 hours
• next morning do a set of 4 stretches and folds
• cover with damp towel and rest for 15 minutes
• do another set of 4 stretches and folds and place into a bowl with high sides lined with parchment paper
• put into fridge uncovered for 10 hours
• put dough into cast iron french oven and score with two intersecting lines
• cover with lid and put into cold oven with an empty cookie sheet on one rack below
• turn oven on to 450 degrees Fahrenheit
• bake for 1 hour covered
• remove cover and continue baking for another 25 minutes
• remove from oven and cool on rack
• for second loaf repeat previous steps adding 1/8 tsp commercial yeast to water and sourdough starter before mixing with the flour and salt
• note: recipe adjusted from sourdough bread recipe from feastingathome.com

The loaf of sourdough with extra yeast was 9.7cm in height and 19.7cm in width, and the one without extra yeast was 8.9cm in height and 18.7cm in width. The one without extra yeast also had bigger air bubbles than the one with extra yeast. The one without extra yeast also had higher crispery ears.

Our analysis is that the loaf with extra yeast rose higher than the loaf without extra yeast. And the one with more yeast is more dense. Also the one with no extra yeast has crisyer ears.

The conclusion is that adding extra yeast will give sourdough a higher rise than not adding extra yeast. And that the one with extra yeast is more dense.

You could use more yeast to make the sourdough rise higher or use less so it doesn't rise as high. This will help you if you are baking sourdough for the first time.

Our sources of error could be the scale is off by a little bit, a little bit of sourdough starter could be left in the bowl or the weather could have affected the dough when it was rising or when was baking.

1. All About Sourdough Starter. https://foodbodsourdough.com/what-is-sourdough-starter/ Accessed March 1, 2026
2. What is Baker's Yeast? Science of Yeast. https://redstaryeast.com/science-of-yeast/#what-is-yeast Accessed March 1, 2026
3. What is Sourdough Bread? https://www.culturedfoodlife.com/what-is-sourdough-bread/?srsltid=AfmBOoqntoZzlav88VPeGqOfI9-aYX_pnjJ5qrxN4SwthepMKiluOFfZ#:\~:text=Sourdough%20is%20bread%20made%20from,yeast%2C%20to%20leaven%20the%20dough. Accessed March 1, 2026
4. Sourdough Bread Recipe. https://www.feastingathome.com/sourdough-bread/

We give acknowledgements to Stella's mom, Stella's dad, and Alison's mother. We would like to give thanks to Stella's and Alison's family for supporting us.