Required Practical 4: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 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 change indicates the presence of starch when using iodine solution?

  From orange to blue-black
• How do you test for sugars like glucose?

  Add Benedict solution and heat in water
• What color does Benedict solution start as?

  Blue
• 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 procedure for testing for proteins?

  1. Take 2 cm cubed of food solution.
  2. Add 2 cm cubed of Biuret solution.
  3. Observe color change from blue to purple/lilac.
• What is the procedure for testing for lipids?

  1. Grind food with distilled water using a mortar and pestle.
  2. Transfer 2 cm cubed of food solution to a test tube.
  3. Add distilled water and ethanol, then shake gently.
  4. Observe 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 safety precaution must be taken when using ethanol?

  No naked flames should be present
• What are the key chemicals used in the tests for carbohydrates, proteins, and lipids?

  • 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: Purple/lilac with Biuret solution
  • Lipids: White cloudy emulsion with ethanol