Required practical 4 : Food tests

• Step 1 : Take the food sample and grind with distilled water using a mortar and pestle to make a paste
• Step 2: transfer the paste to a beaker and add more distilled water. Stir so the chemicals in the food dissolve in the water
• Step 3 : filter the solution to remove suspended food particles
• Testing for starch :

  1. place 2cm^3 of food solution into a test tube
  2. Add a few drops of iodine solution (orange)
  3. ✅if starch is present then the solution will turn blue-black
  4. ❌no starch present the solution will stay orange
• Testing for sugars

  1. Place 2cm^3 of food solution into a test tube
  2. Add 10 drops of Benedict’s solution (blue)
  3. Place the test tube in a beaker and half-fill the beaker with hot water from a kettle, leave for 5 minutes
  4. ✅if sugars are present the solution will turn brick red/yellow/green
  5. ❌no sugars present solution will remain blue
• Testing for proteins

  • Place 2cm^3 of food solution
  • Add 2cm^3 of biuret solution
  • ✅if protein is present the solution will turn purple
  • ❌no protein solution will remain blue
• Testing for lipids :

  • Add 2cm^3 of food solution (unfiltered because lipids molecules stick to filter paper)
  • Add 3 drops of Sudan ||| solution
  • ✅if lipids are present a red stained oil layer appears in the solution
  • ❌no lipids the solution will remain red