food tests

• Benedict's = sugar


  • grind up a piece of food
  • transfer 5cm cubed to a test tube
  • add to a water bath at 75 degrees
  • add benedict's solution using a pipette
  • place the test tube in a water bath and leave for 5 minutes
  • goes from blue to green, yellow, red
  • green/yellow = low amount
  • red = high amount
• Iodine solution = starch


  • grind a food sample
  • transfer 5cm cubed into a test tube
  • add a few drops of iodine solution and gently shake to mix
  • if starch is present, it will change from browny-orange to black or blu-black
• Biuret test = proteins


  • grind a food sample
  • transfer 2cm cubed of sample to test tube
  • add 2cm cubed of biuret solution to solution and gently shake to mix
  • if protein is present, solution will change from blue to purple
• Sudan III = lipids


  • grind a food sample
  • transfer 5cm cubed into a test tube
  • use a pipette to add 3 drops of Sudan III stain solution to the test tube and gently shake to mix
  • if lipids are present, mixture will separate into 2 layers.
  • top layer will be bright red