Food Tests

• What is the first step in preparing a food sample for testing?

  Break it up using a pestle and mortar
• Why do you add distilled water to the ground food sample?

  To dissolve some of the food
• What is the purpose of filtering the food solution?

  To remove solid bits of food
• What are the steps to perform the Benedict's test for reducing sugars?

  1. Prepare a food sample and transfer 5 cm³ to a test tube.
  2. Set a water bath to 75°C.
  3. Add about 10 drops of Benedict's solution.
  4. Place the test tube in the water bath for 5 minutes.
  5. Observe color change from blue to green, yellow, or brick-red.
• What color indicates the presence of reducing sugars in the Benedict's test?

  Green, yellow, or brick-red
• How do you test for starch using iodine solution?

  1. Prepare a food sample and transfer 5 cm³ to a test tube.
  2. Add a few drops of iodine solution.
  3. Gently shake the tube to mix.
  4. Observe color change from browny-orange to black or blue-black.
• What color change indicates the presence of starch in a food sample?

  From browny-orange to black or blue-black
• What is the procedure for the Biuret test for proteins?

  1. Prepare a food sample and transfer 2 cm³ to a test tube.
  2. Add 2 cm³ of biuret solution.
  3. Gently shake to mix.
  4. Observe color change from blue to purple.
• What color indicates the presence of proteins in the Biuret test?

  From blue to purple
• How do you perform the Sudan III test for lipids?

  1. Prepare a food sample and transfer 5 cm³ to a test tube.
  2. Add 3 drops of Sudan III stain solution.
  3. Gently shake the tube.
  4. Observe for a bright red top layer if lipids are present.
• What indicates the presence of lipids in the Sudan III test?

  A bright red top layer forms
• What should you do before starting food tests?

  Conduct a risk assessment
• What types of foods can be tested for reducing sugars?

  Biscuits, cereal, and bread
• What types of foods are rich in starch?

  Pasta, rice, and potatoes
• What types of foods are rich in proteins?

  Meat and cheese
• What types of foods contain lipids?

  Olive oil, margarine, and milk
• What is the volume of food sample used in the Biuret test?

  2 cm³
• What is the volume of food sample used in the Iodine test?

  5 cm³
• What is the volume of food sample used in the Benedict's test?

  5 cm³
• What is the volume of Sudan III stain solution added?

  3 drops
• What temperature should the water bath be set to for the Benedict's test?

  75°C
• What is the purpose of using a funnel lined with filter paper?

  To filter out solid bits of food
• What is the purpose of using a glass rod in the food testing process?

  To stir the mixture
• What should you ensure about the test tube during the Benedict's test?

  It should point away from you