you have a sample of food and wish to determine whether there is protein present. what technique would you use?
You would use the Biuret test to determine whether protein is present in a food sample.
How the Biuret test works
- Proteins contain peptide bonds, which react with copper ions in alkaline solution.
- When you add Biuret reagent (usually a mixture of copper sulfate in alkaline solution) to a protein-containing sample, a violet or purple color appears if protein is present.
Simple school‑level procedure (typical exam answer)
- Grind or mash a small amount of the food and mix it with water in a test tube.
- Add a few drops of copper sulfate solution.
- Add excess sodium hydroxide (caustic soda) solution to make the mixture alkaline.
- Shake and leave for a short time.
- Observation :
- Violet/purple color → protein present.
* No color change (stays blue or pale) → protein absent.
For most school or basic exam questions phrased like “you have a sample of food and wish to determine whether there is protein present. what technique would you use?”, “Biuret test for protein ” is the expected one‑line answer.
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