DECAY

• Milk decay


  Bacteria in milk use enzymes to produce acidic molecules, causing milk to taste sour
• Investigating effect of temperature on milk decay

  1. Use lipase enzyme instead of actual milk decay

  2. Label test tubes: lipase, milk with indicator

  3. Add lipase, milk, sodium carbonate to respective test tubes

  4. Place test tubes in water bath at chosen temperature

  5. Transfer lipase to milk, start timer

  6. Stop timer when milk solution turns yellow
• Experiment

  • Independent variable: temperature
  • Dependent variable: time for milk solution to turn yellow
  • Control variables: volumes of solutions
• Use clean test tube for milk solution in each experiment to avoid traces of lipase from previous experiment
• Difficult to determine exact point to stop timer due to color change, can reduce effect by sharing data and calculating mean
• At low temperatures

  Reaction is slow
• At optimum temperature


  Reaction is fastest
• At temperatures warmer than optimum

  Reaction slows down and may stop completely due to enzyme denaturation
• Decomposing microorganisms work faster in warm conditions but not in hot conditions due to enzyme denaturation