When two drops of copper sulphate and ten drops of caustic soda are added to milk and egg, the colour changes from white to violet. Presence of which of the following components is indicated in the given experiment?

To test the presence of proteins in any substance, 2 drops of copper sulphate and 10 drops of caustic soda are added to the substance. If the colour of the solution does not change, it means proteins are absent. If the colour changes from white to violet, it confirms the presence of proteins. Milk, egg and pulses give positive test for proteins.