Determining the Effects of Browning in Pineapple on Gelatin

Introduction:

Bromelin is an enzyme that is found in pineapple, that degrades protein. When the enzyme is inactivated do to the heating process there is no effect on gelatin. However, when the enzyme is active it will degrade the protein in the gelatin and it will not set properly.

Materials:

2 boxes of flavored gelatin
Boiling water
Fresh pineapple
Canned pineapple
Hot plate
2 - 500 ml beakers
Refrigerator
Stirring rod
Thermometer
Scales
Blender

Procedures:

  1. Heat 125 ml of water to 100 degrees Celsius.
  2. Add 40 g of gelatin.
  3. Stir until dissolved.
  4. Refrigerate for 30 minutes.
  5. Blend 50 g of fresh pineapple.
  6. Stir the fresh pineapple into the gelatin mixture.
  7. Stir again in 15 minutes.
  8. Test the consistency after 2 hours.
  9. Repeat steps 1-8 using canned pineapple instead of fresh pineapple.

Results:

  Consistency of gelatin when pineapple is first added. Consistency of gelatin after 15 minutes. Consistency of gelatin after 2 hours.
Fresh pineapple      
Canned pineapple      

Questions:

  1. When adding pineapple to a gelatin dessert, would you recommend using fresh of canned pineapple? Explain.



  2. What causes the gelatin to return to a liquid state? Explain.



  3. Why does gelatin containing canned pineapple remain in a gelled form?



Extensions:

You may what to try heating fresh pineapple at different temperatures and times to see what the critical points are for enzyme inactivation.

Reference:

Darrow, Edward E. "Student Research Projects in Food Science, Food Technology and Nutrition." Ohio State University. 1989.

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