B7 - milk

• • how temperature affects the rate of decay
  • phenolphtalein is used
  • it is pink when at pH 10 and colourless when below pH 8.3
• 1. measure 5cm of lipase solution and add to test tube
  2. measure 5cm of milk, add to own test tube
  3. add 5 drops of phenolpthalein indicator into test tube with milk
  4. measure 7cm of sodium carbonate solution, add to test tube with milk and indicator - solution in tube will turn alkaline and turn pink
  5. put both tubes in water bath of 30 degrees until reached temperature
  6. use calibrated dropping pipette, put 1cm of lipase solution into milk tube, start stopwatch, stir milk tube with glass rod
  7. solution will turn white, stop stopwatch, record time taken for colour change
• • the experiment should be repeated 3 times each at different temperatures
  • a mean time taken can be calculated at each temperature
• • the rate of decay can be calculated:
  • rate = one thousand/time