Required Practical 4: Food Tests

• What is emphasized about the chemicals used in the tests?

  They are potentially hazardous
• What is the procedure for preparing a food sample for testing?

  1. Grind food sample with distilled water using a mortar and pestle.
  2. Transfer paste to a beaker and add more distilled water.
  3. Stir to dissolve chemicals and food.
  4. Filter to remove suspended food particles.
• What are the two types of carbohydrates mentioned?

  Starch and sugars
• How do you test for starch in a food solution?

  Add iodine solution to the food solution
• What color does iodine turn if starch is present?

  Blue-black
• What color does iodine remain if no starch is present?

  Orange
• How do you test for sugars like glucose?

  Add Benedict solution and heat the mixture
• What color indicates a small amount of sugar in the Benedict test?

  Green
• What color indicates a lot of sugar in the Benedict test?

  Brick red
• What are reducing sugars?

  Sugars that can reduce other substances
• What is the test for proteins?

  Add Biuret solution to the food solution
• What color change indicates the presence of protein?

  Blue to purple or lilac
• What is the procedure for testing lipids?

  1. Grind food sample with distilled water using a mortar and pestle.
  2. Transfer to a test tube without filtering.
  3. Add distilled water and ethanol.
  4. Gently shake the solution.
  5. Look for a white cloudy emulsion.
• What indicates the presence of lipids in the test?

  A white cloudy emulsion forms
• Why do we not filter the solution when testing for lipids?

  Lipid molecules can stick to filter paper
• What is a safety concern when testing for lipids?

  Ethanol is highly flammable