Biology Food 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 indicates the presence of starch when iodine is added?

  Blue-black
• What is the initial color of the iodine solution?

  Orange
• How do you test for sugars like glucose?

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

  Green
• 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 color of the Biuret solution used to test for proteins?

  Blue
• What color change indicates the presence of protein in the Biuret test?

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

  1. Grind food with distilled water using a mortar and pestle.
  2. Transfer to a test tube without filtering.
  3. Add distilled water and ethanol.
  4. Shake gently.
  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 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?

  • Carbohydrates: Iodine solution, Benedict solution
  • Proteins: Biuret solution
  • Lipids: Ethanol, distilled water
• What are the positive results for each food group test?

  • Carbohydrates:
  • Starch: Blue-black with iodine
  • Sugars: Color change with Benedict
  • Proteins: Purple or lilac with Biuret
  • Lipids: White cloudy emulsion with ethanol