The Effect ofTemperature on Bread Yeast Andrew Van Hoof
Background• Yeast – Active Dry Yeast• Invented in WWII to preserve the shelf life of yeast• It is a type of dried yeast that is activated by water.• It is placed in the bread to cause the formation of CO2 which causes the bread to rise.• Without the yeast the bread will not rise and create matzos.• Since the yeast undergoes alcoholic fermentation, there is actually trace amounts of alcohol in bread.
Materials (Recipe)• 1 1/4 cups lukewarm water• 1/4 cup vegetable oil• 1/4 cup honey, molasses, or maple syrup• 3 1/2 cups King Arthur Premium 100% Whole Wheat Flour• 1 packet active dry yeast dissolved in 2 tablespoons of the water in the recipe• 1/4 cup nonfat dried milk• 1 1/4 teaspoons salt
Independent Variable Temperature – one bread loaf was kept at room temperature, which was 68 degrees Fahrenheit, while the other was kept atDough at 0 Minutes about 140 degrees Fahrenheit.
Constants• Yeast – the same active dry yeast was used for both breads.• Recipe timing and materials – the same ingredients and both breads were made simultaneously under the same atmospheric and room conditions.• Both were mixed and cooked in the same type of glass cookware.
What We Did• Ingredients were combined simultaneously so the rising process started for both breads at the same time.• Both were kneaded by hand, and Dough at 0 Minutes placed in a glass bowl and covered with tin foil that had a coat of oil on it to prevent sticking.• We placed bread #2 into an oven at 140°F and placed bread #1 on the counter at 68°F.• We let the yeast go to work.
Data Bread was recorded every 15 minutes for 1.5 hours: Dough at 0 Minutes Dough at 30 Minutes Dough at 60 MinutesDough at 15 Minutes Dough at 45 Minutes Dough at 75 Minutes Dough at 90 Minutes
Data Observations • Over the course of the 1.5 hours, we observed Dough at 30 Minutes bread #2 rising faster than bread #1. • Bread #2 was the bread in the oven. • At 1.25 hours, bread #2 stopped rising, and breadDough at 75 Minutes Dough at 90 Minutes #1 started to catch up to the size of bread #2.
Why Did This Happen?• Bread rises because the yeast in the bread undergoes alcoholic fermentation, which releases The Important Byproduct carbon dioxide gas, causing it to rise.• The yeast take glucose from the other ingredients and use it to make ATP so they can survive through glycolysis.• There are optimum temperatures at which the yeast can process the glucose, making carbon dioxide faster, causing the bread to rise faster.
Results • The glycolysis process that the yeast undergoes to make energy is enzyme mediated. • Enzymes work best at specificDough at 30 Minutes temperature ranges. • Bread #2 was in that ideal temperature range for a while, but it went over that range when it was in the 140 degree oven too long and the enzymes in the bread were denatured. • Bread #1 did not reach the optimum temperature, so it tookDough at 90 Minutes longer for the bread to rise, yet the enzymes did not denature.
Why It Matters• When baking, bakeries need to keep the bread in “warming rooms” so the enzymes can work at optimum temperatures, reducing the time that it takes to make one loaf of bread.• This means that bakeries can make more bread, increasing productivity.