Class 12 Biology - Test for Protein in Food

Aim

To test for the presence of proteins in food samples using the biuret solution.

Materials Required

• Test tubes
• Biuret solution (copper sulfate and sodium hydroxide)
• Food samples (e.g., egg white, milk, and pulses)
• Dropper
• Test tube rack

Image Reference

Procedure

1. Take a small amount of the food sample in a clean test tube.
2. Add a few drops of sodium hydroxide solution to the test tube and mix well.
3. Add a few drops of copper sulfate solution to the mixture and shake gently.
4. Observe the color change in the solution.

Observation

If proteins are present, the solution changes to a violet or purple color. This indicates the presence of peptide bonds in the protein.

Inference

Biuret solution reacts with peptide bonds in proteins to produce a purple color, confirming the presence of proteins in the tested food sample.

Precautions

• Use clean and dry test tubes for accurate results.
• Add the solutions in the specified order (sodium hydroxide first, then copper sulfate).
• Handle chemicals with care and avoid skin contact.

Video Reference