Food tests

• Test for glucose (a reducing sugar)

  • Add Benedict's solution into sample solution in test tube
  • Heat at 60 - 70 °c in water bath for 5 minutes
  • Take test tube out of water bath and observe the colour
  • A positive test will show a colour change from blue to orange or brick red
• Test for starch

  • Add drops of iodine solution to the food sample
  • A positive test will show a colour change from orange-brown to blue-black

• Test for protein

  • Add drops of Biuret solution to the food sample
  • A positive test will show a colour change from blue to purple

• Test for lipids

  • Food sample is mixed with 2cm3 of ethanol and shaken
  • The ethanol is added to an equal volume of cold water
  • A positive test will show a cloudy emulsion forming