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Lab 5 Pineapple Enzymes

Lab 5: Pineapple Enzymes


         Gelatin is the protein that gives Jell-O its texture. Gelatin is a protein, made from the hydrolysis of collagen. Collagen is what makes up much of the connective tissue, tendons, and the protein part of bones in mammals. As a reminder, hydrolysis in proteins is the process of adding a molecule of water to break the bonds between some of the amino acids. Essentially, when one adds water to collagen, they get gelatin.




         Collagen forms a triple helix, where three chains of connected amino acids form weak hydrogen bonds between electronegative oxygen atoms of a carboxyl and the hydrogen atoms of the adjacent chain’s amino groups. The three chains then twist together like three cords in a rope. In gelatin due to hydrolysis by water these three cords open up. Some of the hydrolyzed (broken) ends fray out to tangle with other ropes. Water remains trapped in the strands. The result is a gel, a wiggly semi-solid mass following refrigeration.

            Ever noticed a warning in the directions for Jell-O to NOT add fresh pineapple to the mixture? Doing so will cause the gelatin to remain in the liquid state, even after prolonged refrigeration. This is due to the presence of a certain enzyme, bromelain, in pineapple that destroy the protein gelatin.

          Enzymes are a specific type of proteins that help a reaction to occur. Bromelin, for example, helps in the reaction in which gelatin is broken down.

         As we’ve learned, the function of a protein is related to its 3-dimensional structure. Any alternation in its structure will prevent it from functioning properly. So, what might happen if we were to heat the pineapple prior to adding it to a Jell-O mix? Would the Bromelin enzyme still work? Would the Jell-O still solidify? At which temperature might bromelain stop working? In this lab, we’ll find out. We’ll also do an investigation to see if we can find other fruits besides pineapple that have this gelatin-breaking-down enzyme.


Prelab Procedure (Must be completed for day of lab)


1. Write the date, title, number and purpose of the lab in your notebook.


2. Write the procedure for section A, B, and C into your lab notebook.


3. Create chart A in your laboratory notebook in which you can collect your data for parts A and B. Fill in “Contents” Row.


Test Tube # Contents Solidify: Yes or No? Enzyme Active: Yes or No?
1 (+)      
2 (-)      


3. Create chart B in your laboratory notebook in which you can collect your data for part C (Test tube 7,8,9 and 10). Fill in the “Contents” and “Temperature” Row.


Test Tube # Contents Temp (C) Solidify: Yes or No? Enzyme Active: Yes or No?



4. Answer the following prelab questions.


         A. What is gelatin?

         B. What does the enzyme in pineapple (Bromelain) do to gelatin?

         C. Would you expect the following to solidify after refrigeration? Yes or No?

                  1. A mixture of Jell-O?

                  2. A mixture of Jell-O and pineapple?

                  3. A mixture of Jell-O and heated pineapple?

         D. In order to make sure your results are accurate, you have to know that under          normal circumstances the pineapple enzyme will do as          expected (prevent the          Jell-O          from solidifying). This would be your positive control. Similarly, you have to know that          in the absence of heat (normal circumstances) the Jell-O will do as expected          (solidify). This would be your negative control. Using this information, what should          your positive and negative control test tube have in it?














1. Label all 9 test tubes with your group name.


A. Setting Up Your Controls

2. Label one test tube “+” an another “-“.


3. Add __________________________________to the positive control.


4. Add __________________________________to the negative control.


B. Testing Other Fruits for the Enzyme Bromelain

5. Label 4 test tubes with the 4 fruits other than pineapple that you are going to test (kiwi, orange, banana, and apple).


6. Add a few small chunks of each fruit to its labeled test tube.


7. Add about 3mL Jell-O mix to each.


C. Testing the Effect of Temperature on the Enzyme Bromelain

8. Label 3 test tubes 75 degrees, 85 degrees and 95 degrees.


9. Add 1ml pineapple juice to each.


10. Place test tubes in the correct water bath for 2 minutes.


11. Remove all the test tubes.


12. Add 3ml Jell-O mix to each.


13. Place all 10 labeled test tubes into the refrigerator to solidify (or will they?) overnight.


D. Collect Results- Next Day


14. Remove all your test tubes from the refrigerator. Mark in your data chart A and B whether or not the contents of each test tube solidified. Note: You can always describe the level of solidification if there appears to be a spectrum.


15. Clean up the test tubes. DO NOT allow fruit chunks to go down the drain.












Analysis and Conclusion  


You will be writing a formal lab report for this. More information to come.

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