How will you test the presence of proteins in food items?

The presence of proteins in food can be tested using a chemical test with nitric acid.

First, take a small amount of crushed food in a test tube. Add a few drops of concentrated nitric acid and heat it slightly. If the food turns yellow, it indicates the presence of protein. When ammonium hydroxide is added, the colour changes from yellow to deep orange, confirming the presence of proteins.