Food Tests

• How do you prepare for every type of food test?

  • Grind up the food in a pestle and mortar
  • Transfer the food to a beaker and add distilled water
  • Stir the mixture with a glass rod
  • Filter the solution using a funnel lined with filter paper to get rid of solids
• What chemical is used to test for sugars?

  Benedict's solution
• What two types of sugars are there?

  Reducing and non-reducing
• Which type of sugars does the Benedict's test test for?

  Reducing sugars
• How do you carry out the Benedict's test?

  • Transfer 5cm cubed of the sample to a test tube
  • Prepare a water bath at 75 degrees
  • Add 10 drops of Benedict's solution to the test tube
  • Place the tube in the bath pointing away from you and leave it for 5 minutes
• What is the colour change when testing using the Benedict's solution?

  Blue to green/yellow/brick-red depending on sugar concentration
• What do you test for using iodine solution?

  Starch
• How do you carry out a test using iodine solution?

  • Transfer 5cm cubed of the sample to a test tube
  • Add drops of iodine solution and gently shake
• What is the colour change process for the iodine test?

  Browny-orange to black or blue-black
• What substance do you use to test for proteins?

  Biuret's solution
• How do you carry out the Biuret's test?

  • Add 2cm cubed of your sample to a test tube
  • Add 2cm cubed of Biuret's solution and gently shake
• What is the colour change process for the Biuret test?

  Blue to purple
• What substance does Sudan III stain solution test for?

  Lipids
• How do you carry out a test using Sudan III?

  • Add 5cm cubed of your solution to a test tube
  • Add 3 drops of Sudan III stain solution and gently shake
• How will your sample change during the Sudan III test?

  If lipids are present: the mixture separates into a top red layer and a clear layer