Which of the following reagent is used for testing the presence of protein in food?

1. Analyze the question You are asked to pick the reagent used to test for protein in food. Each option is a reagent for a different food class.

2. Explain the concept Food tests in Biology:

| Food class | Reagent | Positive result | |---|---|---| | Reducing sugar | Benedict's or Fehling's solution (heat) | Brick-red precipitate | | Starch | Iodine solution | Blue-black colour | | Fats and oils | Sudan III (or ethanol emulsion test) | Red staining of fat | | Protein | Millon's reagent (or Biuret test) | Pink/red colour (Millon's), violet/purple (Biuret) |

3. Solution, option by option

• A. Benedict's solution: tests for reducing sugars, not protein.
• B. Fehling's solution: also tests for reducing sugars.
• C. Millon's reagent: reacts with the amino acid tyrosine in proteins and gives a pink to red colour. This is a protein test.
• D. Sudan III: a stain used to detect fats and oils.

4. Answer The correct option is C. Millon's reagent.

5. Exam tip Link each reagent to its food class:

• Benedict and Fehling are for Sugar (both heated).
• Sudan is for Stuff that is greasy (fat).
• Millon's is for Muscle-building food (protein).

Also remember that the Biuret test (NaOH + dilute copper sulphate, giving a violet colour) is another common protein test. If it appears as an option, it is also correct.