Denaturing Proteins Lab (You will write a lab report and email that to me, due
November 19th)
Purpose : To find what acid or heating method denatures the protein the most.
Materials :
Test tubes
Hot plate
Acetic acid
Lemon juice
Ammonia (NH3)
Egg whites
Background: Proteins are large molecules made up of small amino acids. Proteins are
held in a natural shape due to the interaction of side groups on the amino acids from one
part of the molecule to another area of the molecule. These interactions may be hydrogen
bonds or disulfide bonds. We can denature the proteins by disrupting the H-bonds that
are within the structure. When this happens the overall shape of the protein changes and
new properties can be observed. The shape of a protein is associated with food
processing properties, such as solubility, gel formation, and enzyme activity.
In the egg whites the albumin will change from clear to white. We will explore how the
following denature egg albumin.
- heat – done by cooking
- acids & bases – can form ions on some side groups of amino acids.
Procedures:
1. Place 300 mL of water in a 400mL beaker, place on hot plate and turn on medium
heat.
2. Label test tubes #1-4.
3. Place 1mL, using pipette, in each test tube.
4. Place #1 in the hot water bath (the beaker that is on the hotplate), heat til end of
class, observe the changes on the data table.
5. Place 1 mL of acetic acid in test tube #2, observe the changes and record on the data
table.
6. Place 1 mL of lemon juice in test tube #3, observe the changes and record on the
data table.
7. Place 1 mL of ammonia in test tube #4, observe the changes and record on the data
table.
Data Table
Test tube Denaturing method
1
Heat
2
Acetic acid
3
Lemon juice
4
Ammonia
Observation
Post Lab Questions:
1. Which method appeared to have the most dramatic denaturing affect on egg
albumin? Why do you think this method had a greater affect?
2. Research online a picture or chemical equation that shows the denaturing process of
the method that worked the best from question 1. (paste in lab report)
3. Of the methods you tested, which would be more likely to be used in the food
industry?
4. Research cream of tartar and how it affects egg whites when making meringue,
explain the process.
Conclusion :
It was found in this lab that…