Which test would give a positive result for the presence of protein in a sample of cooked saltfish?

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Question

Which test would give a positive result for the presence of protein in a sample of cooked saltfish?

Accepted Answer

Add sodium hydroxide solution and copper sulfate solution; observe for a purple colour — Award 1 mark for correct identification. The biuret test (sodium hydroxide + copper sulfate) produces a purple/violet colour in the presence of protein. A is incorrect as this is the test for starch. B is incorrect as this is the test for reducing sugars. D is incorrect as this is the emulsion test for lipids.

Answer

Add Benedict's solution and heat; observe for a brick-red precipitate

Answer

Add sodium hydroxide solution and copper sulfate solution; observe for a purple colour

Answer

Add ethanol and shake; observe for a cloudy white emulsion

Answer

Add iodine solution and observe for a blue-black colour

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