Which chemicals are used for protein testing?

The Biuret test is used to detect proteins in food. It requires two chemicals: copper sulphate solution (CuSO₄) and sodium hydroxide solution (NaOH).

During the test, a few drops of copper sulphate solution and sodium hydroxide solution are added to the food sample. If proteins are present, these chemicals react with the peptide bonds in proteins and produce a violet or purple colour. If proteins are absent, the solution remains blue. This test is commonly performed in school science laboratories to identify protein-rich foods.