Food tests

• What is the aim of the food tests practical?

  To conduct qualitative chemical tests for starch, reducing sugars, proteins, and lipids.
• What equipment is needed for the iodine test for starch?

  • Food sample
  • A test tube
  • Iodine solution (0.01 mol/dm³)
  • Pipettes
• What indicates the presence of starch in the iodine test?

  The solution turns from brown to blue-black.
• What equipment is required for the Benedict's test for reducing sugars?

  • Food sample
  • A test tube
  • Benedict's solution
  • Hot water bath
  • Thermometer
  • Pipettes
• What color change occurs if reducing sugar is present in the Benedict's test?

  A brick red precipitate is formed.
• What happens to the solution in the Benedict's test if reducing sugar is absent?

  The solution remains blue.
• What equipment is needed to test for protein?

  • A test tube
  • A 10cm³ measuring cylinder
  • Biuret solution
• What indicates the presence of protein in the Biuret test?

  The solution turns from blue to purple.
• What equipment is required for the test for lipids?

  • Food sample
  • Test tube
  • Ethanol
  • Distilled water
• What is the result of the emulsion test if lipids are present?

  A white emulsion is formed on the surface of the mixture.
• What is the first step in the method for testing lipids?

  Add a few cm³ of ethanol to the food sample.
• What are the sources of error in the Benedict's test and Biuret test?


  • Colour change may be subtle and difficult to judge.
  • Low concentration of the tested molecule can affect results.
• What safety precautions should be taken during the Benedict's test?


  • Tie hair back and wear safety goggles.
  • Handle Biuret solution with care due to its poisonous and corrosive nature.
  • Keep ethanol solution away from flames as it is highly flammable.