food tests

• What do you use to test for reducing sugars?

  Benedict's solution
• What do you use to test for starch?

  Iodine
• What do you use to test for proteins?

  Biuret's reagent
• What do you use to test for lipids?

  Ethanol
• What are the safety precautions for this experiment?

  Tie hair back and wear safety goggles when performing the Benedict's test using a bunsen burner and a hot water bath

  Handle Biuret solution with care - it contains copper sulphate (poisonous) and sodium hydroxide (corrosive). Wash immediately if it comes into contact with skin

  Keep ethanol solution away from flames as it is highly flammable
• What are the steps for the iodine test for starch?

  Put a food sample in a test tube.

  Add a few drops of iodine solution to the food sample using a pipette

  If starch is present, the solution turns from brown to blue-black
• What are the steps for the Benedict's test for reducing sugars?

  Add an equal volume or excess of Benedict's solution to the food sample in a test tube

  Place in a hot water bath for a few minutes

  If reducing sugar is present, a brick red precipitate is formed, is not, the solution remains blue
• What are the steps for the Biuret's test for proteins?

  Add a few drops of Biuret's reagent (sodium hydroxide and copper sulphate) to the food sample in a test tube

  Shake the solution to mix and wait for a few minutes

  If protein is present, the solution turns from blue to purple
• What are the steps for the emulsion test for lipids?

  Add a few cm^3 of ethanol to the food sample

  Pour this mixture into a test tube of equal volumes of distilled water

  If lipids are present, a white emulsion is formed on the surface of the mixture.