Measuring and Manipulating
the pH Level of Egg Yolks
Lab Protocol: pH Testing
Food Safety Scientist Curriculum
This project was supported by the USDA NIFA grant number 2011-38411-30625
© 2014 Board of Regents, South Dakota State University
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Equipment

1 Dozen Hard Boiled Eggs

7-Sampling Cups

Water

Quick Test pH Strips

Mixing Bowl

Whisk

Measuring Cups

Writing Utensil
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Preparing Samples
1.
2.
Remove the egg yolks from the hard boiled eggs and
break down using a mortar & pestle or a whisk.
Add 1 cup of water to yolks and whisk together until a
slurry is formed.
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Procedure
Sample
Egg Yolk
Slurry (mL)
Vinegar (mL)
Water (mL)
Standard
25
--------------------
--------------------
#1
25
--------------------
5
#2
25
--------------------
10
#3
25
--------------------
15
#4
25
5
#5
25
10
#6
25
15
Prepare the samples as shown above and label each one
3
2
1
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4
5
6
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Conversions
If beakers or funnels are unavailable, household
items such as measuring spoons can be used. The
following conversions include:
Metric Units
5 mL
10 mL
15 mL
25 mL
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Conversion to
Tablespoons/
Teaspoons
1 tsp.
2 tsp.
1 TBS.
2 tsp. + 1 TBS.
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Using pH Test Strips
1.
Cut 7-pH test strips 8 cm
long for each sample
including the standard
2.
Dip each strip in the
sample and remove
immediately
3.
Compare the color of the
strip to the standard
included with the strip
dispenser.
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pH Meter (field unit)
 Using
a pH meter is also an
effective instrument for
testing the pH of foods
 It
is important to calibrate
the meter before use to
ensure accuracy
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Microorganisms: survival and
growth



Similar to humans, microorganisms need nourishment and ideal
conditions to grow
Intrinsic Factors: Inherent parts of plant & animal tissue
Extrinsic Factors: Properties of storage environment that affect
both the foods and the environment
INTRINSIC FACTORS
EXTRINSIC FACTORS
pH
Temperature of storage
Moisture (aW)
Presence/Concentration of Gasses
Oxidation-Reduction Potential
Presence & Activities of other
microorganisms
Nutrients
Antimicrobial Constituents
Relative Humidity of environment
Biological Structures
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Discussion Questions
1.
What solutions, other than vinegar, would increase the acidity?
2.
Why is it important to have a higher level of acidity when
preserving food?
3.
What controls the growth of microorganisms other than
changing the pH?
4.
The pH range has an inverse relationship to acidity, what does
this mean?
5.
Do you think there would be a significant change in taste after
adding the vinegar? Why or Why not?
6.
If a company is developing a salsa that would be shelf stable in a
jar, what pH range does it need to be in and why?
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