Food tests

• Why must safety goggles be worn during the tests?

  Because all chemicals are potentially hazardous
• What are the key things to learn for the tests?

  • Chemicals used for each food group
  • Positive results of the tests
• What is the first step in preparing a food sample for testing?

  Grind the food sample with distilled water
• What is the purpose of filtering the solution after grinding the food sample?

  To remove suspended food particles
• What do carbohydrates include?

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

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

  Blue-black
• What color indicates no starch is present in the iodine test?

  Orange
• How do you test for sugars like glucose?

  Add Benedict solution and heat the mixture
• What does a green color in the Benedict test indicate?

  A small amount of sugar is present
• What does a brick red color in the Benedict test indicate?

  A lot of sugar is present
• What type of sugars does the Benedict test work for?

  Reducing sugars like glucose
• What is the test for proteins?

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

  From blue to purple or lilac
• How do you test for lipids in a food sample?

  Add ethanol and distilled water, then shake
• What indicates the presence of lipids in the emulsion 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 safety precaution must be taken when using ethanol?

  No naked flames should be present
• What are the chemical tests for carbohydrates, proteins, and lipids?

  • Carbohydrates: Iodine and Benedict tests
  • Proteins: Biuret test
  • Lipids: Emulsion test with ethanol
• What are the steps for preparing a food sample for testing?

  1. Grind food with distilled water
  2. Transfer to a beaker and add more water
  3. Stir to dissolve chemicals
  4. Filter to remove suspended particles