Proteins
- Label the test tubes with the food materials that you plan to test for protein.
- Add the sample of food to each tube, then add 2cm2 of distilled water. Put the clean bung in and shake carefully at least 10 times.
- Add 10 drops of biuret reagent to the test solution without the pipette touching the inside of the test tube.
- Observe the test solution for a purple/violet or blue colour. Record your observations and deductions from the biuret test in a table.
If a protein is present there will be a colour change from blue to violet or purple.
The colour change is due to two or more peptide bonds in a compound.