food tests

• what is the basic method for all food tests?

  break food up with a pestle and mortar

  put it in a beaker with distilled water

  Stir with a glass rod (so the food dissolves)

  Filter with a funnel lined with filter paper

  Add food sample to test tube

  Add solution to test tube
• what tests for starch?

  iodine solution
• what tests for proteins?

  Biuret test
• what tests for sugars?

  Benedict's test
• what colours does iodine solution turn from and to if starch is present?

  from brown/orange to Blue-black
• what colours does benedics solution turn from and to if starch is present?

  from blue to green, yellow or brick-red
• what colours does biuret solution turn from and to if starch is present?

  from blue to purple
• how much of the food sample do you add to the test tube?

  biuret test - 2cm

  iodine solution - 5cm

  Benedict’s test - 5cm
• how much of the solutions should you add to the test tube?

  biuret test - 2cm

  iodine solution - a few drops

  Benedict’s test - 10 drops
• what should you do for the Benedict’s test that you don’t do any other?

  prepare a water bath at 75 Celsius and leave the test tube in for five minutes
• what should you do for the other tests that you don’t do for Benedict‘s test?

  gently shake the test tube