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Flat breads were being made long before the Egyptians baked with yeast between 2,000 and 3,000 B.C. But yeast transforms the flavor and texture of breads. Try baking the focaccia recipe without the yeast as it may have once been.

In the U.S., yeast was first grown, harvested and packaged as compressed (fresh) yeast for baking in 1868 by Fleischmann brothers and James Gaff. In 1876, French scientist Louis Pasteur discovered yeast causes fermentation. When yeast consumes sugar and oxygen it produces alcohol and carbon dioxide. In 1942, dry yeast was developed especially to help feed troops in WWII. Today we have wonderful dry yeasts—active and fast rising or instant. Some bakers still use compressed, or fresh yeast. Learn more about what yeast needs for fermentation.

Yeast test 1:

Yeast is a living fungus. It requires food, warmth and air for growth.

How will yeast growth vary when fed water, sugar, flour, salt or nothing?

Control: Water amount (1/4 cup/2 oz) and temperature (100-105 degrees F) added; use same yeast container and temperature (105 degrees F)

State your hypothesis for each bowl.


  1. Measure into identical sized bowls:
    Bowl #1: 1 teaspoon active dry yeast
    Bowl #2: 1 teaspoon active dry yeast+1 teaspoon sugar
    Bowl #3: 1 teaspoon active dry yeast+1 teaspoon flour
    Bowl #4: 1 teaspoon active dry yeast + 1/4 teaspoon salt
    Bowl #5: 1 teaspoon active dry yeast+1 teaspoon cinnamon
  2. Take and record the temperature of the water.
  3. Measure 2 oz. (1/4 cup or 62ml) water into each bowl.
  4. Stir to completely moisten the yeast in each bowl. Scrape each spoon as needed. Do not stir again.
  5. Observe and record yeast activity in each bowl at timed intervals—5, 10, 15, and 30 minutes.
  6. Create a chart or bar graph of what you saw.
  7. Write a one-page report of what you observed and why the yeast grew as it did in the environments provided.

Yeast Test 2:

Impact of Water Temperature on Yeast

Question: Yeast is a living fungus. What impact on growth will water
temperature make?

Control: Type of bowl and yeast used, amounts of yeast and sugar

Variable: Temperature of water

State your hypothesis for each bowl.


  1. In five bowls, measure 1 teaspoon active dry yeast and ½ teaspoon sugar
  2. Prepare five 1 quart pitchers of water—Cold (50-65 degrees F); cool (65-75 degrees F.);
    lukewarm (95 to 105 degrees F); warm (105 to 115 degrees F); very warm (145 to 155 degrees F)
  3. Stir ¼ cup water from one of each temperature water into a bowl. Label each bowl with the water temperature.
  4. At 5, 10 and 15 minute intervals observe and record what you see in each bowl.
  5. Touch the water in each pitcher. Can you tell which ones would be warm enough for good yeast growth? Which ones would retard or kill yeast? Describe why it is important to use a thermometer to measure liquid temperatures when working with yeast?
    6. Prepare a report. Include what you observed and whether your hypotheses for each bowl was correct. If not, why? Was touching the water to see if it was the right temperature accurate enough? Why or why not?

Baking for Success
These yeast experiments are excerpted from Baking for Success! More great classroom ideas are featured in this video with an 18 page lesson/activity book.
View this excellent teaching tool! Order form.