2. 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.
3. 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
4. Independent Variable
Temperature – one
bread loaf was kept at
room temperature,
which was 68 degrees
Fahrenheit, while the
other was kept at
Dough at 0 Minutes
about 140 degrees
Fahrenheit.
5. 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.
6. 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.
7. Data
Bread was recorded every 15 minutes for 1.5 hours:
Dough at 0 Minutes Dough at 30 Minutes Dough at 60 Minutes
Dough at 15 Minutes Dough at 45 Minutes Dough at 75 Minutes
Dough at 90 Minutes
8. 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 bread
Dough at 75 Minutes Dough at 90 Minutes #1 started to catch up to
the size of bread #2.
9. 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.
10. Results
• The glycolysis process that the
yeast undergoes to make energy
is enzyme mediated.
• Enzymes work best at specific
Dough 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 took
Dough at 90 Minutes longer for the bread to rise, yet
the enzymes did not denature.
11. 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.
