Biuret Test for Protein

Task: Determine if protein is present in food samples.

Method:

1. Put food samples in test tubes. If they are in dry solid state, crush and mix them with water.

2. Using a pipette, add about 2 cm3 of solution of NaOH.

3. Before adding the next solution, plug the tube and shake its contents thoroughly. Using a pipette, slowly run about 0.5 cm3 of copper sulfate solution down the wall of the tube.

4. To see change in color, shake the tube slightly.

Results:

From left to right: egg yolk, egg white, chicken, flour, rice crispies, yoghurt.

Conclusion: We can say that the egg white contains the most protein, because the coloration changed the most. Flour and rice crispies seemed to contain little to no protein. From the color change in the bottom part of egg yolk, we can say that it probably contains protein, but it had not fully mixed with the solutions, therefore I can not be certain. Chicken and yoghurt contain protein.

Evaluation: To get clearer results on the egg yolk, I would try beating it up in water more before testing it and I would add more NaOH solution.