Food Tests

• Testing for Starch

  Use Iodine Solution

  If positive it turns from orangey brown to blue/black
• Testing for Glucose

  Benedicts Solution

  If positive turns from blue to layers of yellow orange red with red layer at top
• Testing for Proteins

  Biuret Reagent

  If positive goes from blue to lilac or purple
• Testing for Lipids

  Ethanol and water

  If positive turns from no emulsion to white emulsion(layer) forms
• How to prepare a sample?

  • To do this:
  • Break up the food using a pestle and mortar
  • Transfer to a test tube and add distilled water
  • Mix the food with the water by stirring with a glass rod
  • Filter the mixture using a funnel and filter paper, collecting the solution
  • Proceed with the food tests
• Method of Testing Glucose

  1.Set up a traditional water bath using a Bunsen burner (water bath top of Bunsen burner)

  2.Add food sample to a test tube with a few drops of Benedicts solution

  3.Place in water bath at 80c for 5 mins and if glucose is present,colour change will appear.
• Method for testing starch

  1.Add food sample to test tube

  2.Add few drops of Iodine solution

  3.If starch present,note down colour change
• Method for testing Lipids

  1.Add food sample to test tube

  2.Add few drops of distilled water and few drops of ethanol

  3.Shake solution gently and if there’s lipids,note down colour change.

  Note:Ethanol is highly flammable
• Method for testing protein

  1.Add food sample to a test tube

  2.Add a few drops of biuret A and biuret B

  3.If proteins there,note down colour change