Food Tests

• What should you be able to describe by the end of the video?

  How to carry out chemical tests
• What is the focus of the required practical mentioned?

  The chemical tests for carbohydrates, proteins, and lipids
• What must be worn due to the hazardous nature of the chemicals?

  Safety goggles
• 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 main 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 indicates no starch is present in the iodine test?

  Orange
• How do you test for sugars like glucose?

  Add Benedict solution and heat in water
• 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
• 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?

  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.
• Why do we not filter the solution when testing for lipids?

  Lipid molecules stick to filter paper
• What indicates the presence of lipids in the lipid test?

  A white cloudy emulsion forms
• What is a safety precaution when using ethanol in lipid testing?

  No naked flames should be present
• What are the key chemicals used in food tests?

  • Iodine solution for starch
  • Benedict solution for sugars
  • Biuret solution for proteins
  • Ethanol for lipids
• What are the positive results for each food test?

  • Starch: Blue-black with iodine
  • Sugars: Color change with Benedict solution
  • Proteins: Blue to purple with Biuret solution
  • Lipids: White cloudy emulsion with ethanol