How to Test for Protein Quantity in Food

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Along with carbohydrates, fat, fiber, vitamins and minerals, protein is an essential element in your daily diet. Your body needs protein to build strong bones and muscles. Although most foods have nutrition labeling that lists the protein content, you can test for it yourself using a chemical called biuret reagent. When the copper ions in biuret reagent react with peptide bonds in proteins, the solution will take on a pink or purple color. This is a fun science experiment to do with any student; younger children should be strictly supervised.

Add a small amount of water to the food to be tested in order to create a liquid or paste to which the reagent can be added.

Place 40 drops of the food mixture in a test tube or other small container.

Add three drops of biuret reagent to the test tube. Shake gently if needed to mix the solutions.

Check for color changes. If the food contains protein, the solution will turn pink or purple.


Wear rubber gloves when handling biuret reagent; it can stain skin.