Effect of heat on proteins Flashcards
What is the effect of hear on proteins?
Proteins denature in the presence of heat, denaturation is followed by coagulation. Proteins tend to coagulate and show turbidity in the dispersion system.
What did we do in the practical?
We filtered egg whites from a aqueous solution of egg whites. We placed 3 test tubes of 5ml egg whites in water bath for half an hours at 55,65 and 75 degree Celsius.
After cooling the samples with tap water, read the absorbance of samples at 450nm to measure the absorbance of the 3 samples. We then drew a graph of temperature against absorbance.
Define protein denaturation
A permanent change of secondary, tertiary and quaternary structure in a protein.
Describe the process of egg-white denaturation
Denatured egg whites unfold and tangle together, forming a mesh. Liquid form suggest that the proteins are yet to solidify.
At 65 degree Celsius, egg whites begin to coagulate, solution begins to thicken and solidify into a translucent form, white threads begin to form throughout the protein solution. They intertwine into a big white structure.
Fun quiz how do protein denaturation form meringues
When you add air through beating egg whites, the protein molecules uncurl due to breakage of hydrogen bonds so that the water-loving parts immerse themselves in the water and the water-fearing parts can stick out into the air. This traps airs in air pockets throughout the egg white.
State 3 factors that denature egg whites
Exposure to UV light or high frequency electromagnetic waves
Extreme pH changes in the medium
Exposure to extreme heat
Can also be exposure to certain organic solvents like ethanol and oxidizing reducing agent
Describe the graph of the effect of heat on absorbance of egg whites at various temperatures
The relationship between the temperature and denaturation is non-linear, denaturation increases as temperature increases.
Denaturation vs temperature graph follows a decreasing curve with a positive slope. The 4 phases of the curve follow slow acceleration in the beginning of 55 degree Celsius, fast acceleration (55-65 degree Celsius), deceleration phase (65-75 degree Celsius) and linear stop phase at the end of the denaturation process (beyond 80 degree Celsius)
