How can we test the presence of proteins in food?

The presence of proteins in food can be tested using the Biuret test. Take a small amount of the food sample, add a few drops of copper sulphate solution followed by sodium hydroxide solution, and mix gently.

If proteins are present, the solution changes from blue to violet or purple. If there are no proteins, the solution remains blue. The Biuret test is a standard laboratory method used in school science to identify proteins in foods such as milk, eggs, pulses, and beans.