Denaturation temperature of egg white
Have you ever prepared scrambled eggs? In this experiment we look at what happens to the
white of an egg as it is heated.
Denaturation (also called "coagulation" in the literature) is the production of a structural change in a
protein or nucleic acid that results from the reduction or loss of its biological properties. Denaturation can be caused by heat,
chemicals or extremes of pH. The differences between raw and boiled eggs are largely a result of denaturation
In this experiment we try to determine the temperature at which the white of an egg coagulates.
- use the DAQ system to measure temperature and light level changes during heating of the white of an egg.
Specific equipment required
1 - temperature sensor; 2 - light sensor; 3 - spotlight or pocket torch; 4 - beaker with water;
5 - test tube with the egg white; 6 - cooking stove.
In addition, one needs the eProlab CMC-S3
interface and the eProlab data acquisition system [Alternative interfaces and DAQ systems can be used if available].
Immerse the temperature sensor and the test tube with raw white of an egg into the beaker
with cold water. To gain correct data it is necessary to place the temperature sensor close to the test tube because
the temperature of white of an egg rises slower than the water temperature.
Place the spotlight and the light sensor on stands so that emitted light passes through
the test tube and strikes the light sensor. Pay attention to the light source; the intensity of the light
source must remain constant during the experiment.
Measure temperature and light level changes vs. time for about 10 minutes until egg white
begins to coagulate.
Click here for a preconfigured e-ProLab file
Example of e-ProLab file for coagulation of egg white
Example curve for coagulation of egg white
Analysis and discussion
- Watch the light level changes when the white of the egg coagulates.
- From the obtained curves of temperature and light level versus time,
determine the egg white coagulation temperature.
- Compare the obtained temperature of egg white coagulation with values quoted
in the literature.
- To obtain more accurate data try to immerse the temperature sensor into the white of
an egg and repeat the experiment.
When proteins are heated to over 50 °C or subjected to strong acids or alkalis, proteins lose their specific
tertiary structure and may form insoluble coagulates, e. g. egg white. This usually inactivates their biological properties.
Proteins are a large group of organic compounds found in all living organisms. They comprise carbon, hydrogen, oxygen, and
nitrogen and most also contain sulphur. Molecular weights range from 6000 to several million.
Albumins are one of the groups of globular proteins that are soluble in water but form insoluble coagulates when heated.
Albumins occur in egg white, blood, milk and plants. Serum albumins, which constitute about 55% of blood plasma protein,
help regulate the osmotic pressure and hence plasma volume. They also bind and transport fatty acids. a-lactalbumin is one of
the proteins in milk.
References and links