The Effect of Different Levels of pH on the Fermentation of Yeast

Report
The Effect of Different Levels of
pH on the Fermentation of Yeast
By Rachel Koch
Hypothesis and Problem Statement
Problem:
How do different levels of pH in the
environment around yeast effect its
fermentation?
Hypothesis:
If the environment around the yeast has a
higher pH, then the yeast will create more
CO2.
Background Research

Yeast: microorganism, Eukaryotic domain and
the Fungi kingdom

Baker’s yeast: digests sugar

Fermentation: release carbon dioxide

Energy and warmth for fermentation

Dough rising is result of fermentation
Design Diagram
Title: The Effect of Different Levels of PH
on the Fermentation of Yeast
 Hypothesis: If the environment around
the yeast has a higher pH, then the yeast
will create more CO2.

Levels
pH of 5
pH of 6
pH of 7
(control)
pH of 8
Trials
5
5
5
5
Design Diagram cont.
IV: pH level
 DV: Height of dough(cm)
 Constants: Ingredients in dough (besides
IV), the measurements of each ingredient,
temperature at which the dough is placed
to ferment and the amount of time the
yeast ferments.

Materials










Flour
Sugar
Instant yeast
Warm water/solution
Oil
Salt
Ruler
HCl
NaOH
Oven
Procedure
•
Prepare pH solutions in lab with the
instructor using NaOH for basic solutions
and HCl for acidic solutions.
1.
Heat water/solution to 35 degrees C.
2. Add flour, sugar, oil, yeast and salt to
the warmed water/solution.
Procedure cont.
3. Knead dough for about 8 minutes.
4.
Measure the height of the dough.
5. Store dough in a warm place for 45
minutes to allow yeast to ferment.
Procedure cont. 2

Put dough in the oven set to 54
degrees C and turn the oven off
6. Measure the final height that the
dough raises with a ruler.
Photodocumentation
Data
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Averages
pH 5
pH 6
4.5 cm
5 cm
5 cm
5 cm
4.5 cm
4.8 cm
2 cm
3 cm
3 cm
3.5 cm
2.5 cm
2.8 cm
pH 7
(control)
4.5 cm
4 cm
4 cm
4.5 cm
4 cm
4.2 cm
pH 8
3.5 cm
3 cm
3.5 cm
3 cm
3 cm
3.2 cm
Averages
PH 5: 4.8 cm
 PH 6: 2.8 cm
 PH 7 (control): 4.2 cm
 PH 8: 3.2 cm

Graph
Height of dough in cm.
6
The Effect of Different Levels of pH
on the Fermentation of Yeast
5
4
3
2
1
0
pH 5
pH 6
Level of pH
pH 7
pH 8
Statistical Analysis
ANOVA
Source Sum of
of
squares
Variati
on
Between 13.14
Degrees Mean
F
of
Squares
Freedom
Signifi
cance
3
4.379
0.000
Error
2.1
16
0.1313
Total
15.24
19
33.37
Conclusions

Hypothesis did not support data

Ideal environment is pH 4-6

Yeast ferments better in acidic substances

Data is inaccurate
Possible Errors

Oven temp. wasn’t exactly the same every
time

Measurements might not have been exact

Measured every half centimeter
Improvements

Could buy an alternative heating devise

Measure ingredients more carefully

Measure the height to a tenth of a cm
Reasoning

Like to bake

Thought it was interesting that yeast
makes dough rise
Extensions

Test other factors that effect yeast
fermentation, like:
oTemperature
oAmount of sugar
Acknowledgements
Mrs. P
o Preparing solutions
o Helping

Parents
o Bought ingredients

Bibliography
"Basic Bread." PrismNet : Austin TX VOIP, Broadband Colocation, Web Hosting. Web. 05 Oct.
2010. <http://www.io.com/~sjohn/bread.htm>.
"Fermentation." Utah State University: Intermountain Herbarium. Web. 04 Oct. 2010.
<http://herbarium.usu.edu/fungi/funfacts/Fermentation.htm>.
"What Are Yeasts?" Saccharomyces Genome Database. Web. 05 Oct. 2010.
<http://www.yeastgenome.org/VL-what_are_yeast.html>.
Campbell, Neil A., Jane B. Reece, Lawrence G. Mitchell, and Martha R. Taylor. Biology
Concepts & Connections. San Francisco: Benjamin Cummings, 2003. Print.
"Factors Effecting Fermentation." Web. 19 Dec. 2010.
<http://home.earthlink.net/~ggda/factors_effecting_fermentation.htm>.
"Yeast Fermentation in Baked Goods." Dakota Yeast. Web. 20 Dec. 2010.
<http://www.dakotayeast.com/help-fermentation.html>.

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