Food Tests

• Reducing sugars: Benedict's test

  1. Add Benedict's solution

  2. Heat mixture

  3. Colour change blue to green to yellow to orange to brick red (colorimetry can be used for a more quantitative Benedict's test result)
• Non-reducing sugars


  • No colour change after Benedict's test
  • Add dilute HCl then neutralise (with sodium hydrogencarbonate)- acid breaks down non-reducing sugars into monosaccharides
  • Head and observe colour change
• Emulsion test (for lipids)

  1. Add ethanol and shake

  2. Pour solution into water

  3. If milky white emulsion forms, lipid is present (as lipids are insoluble in water, so immiscible in water)
• Biuret test (for proteins)

  1. Make solution alkaline, by adding a few drops of sodium hydroxide

  2. Add copper (II) sulphate/ Biuret reagent

  3. If blue to purple, proteins are present
• Iodine test (for starch)


  1. Add aqueous iodine solution to a sample

  2. If starch is present, brown-orange colour change to dark blue-black