Aim: To test is a sample of food contains protein.
Equipment: test tube, sodium hydroxide (NaOH), copper sulfate (CuSO4), food sample (milk).
Method:
1. Place about 2 mL of the sample into a test tube and add 5 drops of sodium hydroxide.
2. Add 5 drops of copper sulfate.
3. Shake the test tube gently from side to side.
Results: If the solution remains blue, then no protein is present. If the solution changes to a purple colour then protein is present in the sample.
Discussion: The Biuret test is based on the ability of Cu (II) ions to form a violet-coloured protein after you heat the food.
Pictures:
Egg
Before heating: After heating:
Milk
Before heating: After putting the Biuret: After heating:
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