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Project Summary

Difficulty	4
Time required	Very Short (a day or less)
Prerequisites	None
Material Availability	Readily Available
Cost	Very Low (under $20)
Safety	Adult supervision is recommended for making the gelatin, which involves using boiling water.

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Abstract

Objective

The purpose of this project is to test the hypothesis that food items containing a protein-digesting enzyme will prevent gelatin from solidifying.

Introduction

If you like making gelatin for dessert, you may have noticed that the box recommends against adding certain kinds of fresh or frozen fruit, e.g., pineapple, kiwi, mango, ginger root, papaya, figs, or guava. This is because these fruits contain the protein-digesting enzymes papain or bromelain that can prevent the gelatin from setting.

So why would a protein-digesting enzyme interfere with the setting of gelatin? To find out, you should do some background research on the ingredients that go into gelatin, and how it normally sets (see Howstuffworks, 2006, for a good start).

Although papain and bromelain can digest proteins, these enzymes themselves are proteins. Most proteins can be inactivated by denaturation. Denaturation changes the structure of the protein, without breaking the chemical bonds between the amino acids that make up the protein backbone. Exposure to heat is one method of denaturing proteins. A good example is cooking an egg. When the egg is raw, the egg white—which has lots of proteins called albumins—is transparent and liquid, but after cooking it becomes opaque and solid. In the case of eggs (and most enzymes) denaturation of the protein causes an irreversible change. Most enzymes are inactivated by denaturation.

In this science fair project, you will perform two tests.

• First, you will choose one or more of the fresh fruits from the list above to see if they prevent gelatin from setting.
• Second, in order to test if enzyme activity is responsible for the effect, you will also test the fruit(s) after cooking (to denature any enzymes present in the fruit).

With this science fair project, you'll get to enjoy some of your results as dessert!

Terms, Concepts and Questions to Start Background Research

• Gelatin
• Protein
• Enzyme
• Protease
• Papain
• Bromelain
• Control

More advanced students should also study:

• proteolysis,
• protein denaturation,
• protein structure (primary, secondary, tertiary, quaternary).

Questions

• How do papain and bromelain digest proteins?

Bibliography

• Howstuffworks.com. (2006). What Exactly Is Jell-O Made From? Retrieved July 11, 2006, from http://home.howstuffworks.com/question557.htm
• Wikipedia Contributors. (2006, July 14). Papain. Wikipedia: The Free Encyclopedia. Retrieved July 11, 2006, from http://en.wikipedia.org/w/index.php?title=Papain&oldid=63703978
• Wikipedia Contributors. (2006, June 30.) Denaturation (Biochemistry). Wikipedia: The Free Encyclopedia. Retrieved July 11, 2006, from http://en.wikipedia.org/w/index.php?title=Denaturation_%28biochemistry%29&oldid=61308564

Materials and Equipment

• Clear plastic cups (6 to test one fruit and create a control, and 4 more for each additional fruit you will test)
• Fresh fruit, such as pineapple, kiwi, mango, ginger root, papaya, figs, or guava
• Two sauce pans
• Oven mitt
• Gelatin mix
• Lab notebook
• Optional: You can try papain tablets, available at vitamin/health food stores, as a positive control.

Experimental Procedure

Safety Note. Preparing gelatin involves pouring and stirring boiling hot water. Adult supervision or assistance is highly recommended.

1. Determine how many different fruits you will be testing, then calculate the number of cups of gelatin to make.
   • For each fruit tested, you should make at least four cups of gelatin: two for uncooked fruit and two for cooked fruit.
   • You will also need two extra cups for plain gelatin (as a negative control, to make sure that the gelatin alone sets properly).
   • If you want to try different amounts of each fruit, you will need 4 cups for each amount tested (again, 2 cups for cooked fruit, and 2 cups for uncooked fruit). You will also need extra cups for ground-up papain tablets, if you are using them.
   • Label two cups Fresh and two cups Cooked, and include the type of fruit and amount of fruit on all four cups.
   • Make the gelatin according to the instructions on the box.
   • For each type and amount of fruit to be tested, add fresh (uncooked) fruit to two cups.
   • For each type and amount of fruit to be tested, add fruit that you have cooked (boiled or steamed for 5 minutes) to two cups. Use the same amount of cooked fruit as you used for the fresh fruit.
   • Optional: grind up two papain tablets and dissolve in a small amount of water. Add equal parts of this solution to two cups of gelatin as a positive control. Mix well.
   • Finally, add gelatin only to two cups. This is your negative control (to make sure that the gelatin alone sets properly).
   • Refrigerate all of the cups, noting the time in your lab notebook.
   • Check the consistency of the gelatin in each cup at regular intervals (once or twice an hour). Examine the gelatin carefully and record your observations in your lab notebook. In which conditions does the gelatin set? In which conditions does the gelatin remain as liquid? Are there any in-between cases?

Variations

• Does freezing fruit denature protein-digesting enzymes? Design an experiment to compare the enzyme activity of fresh and frozen pineapple.
• Do other methods of fruit processing denature enzymes? How about drying or canning? Design an experiment to find out.
• Design an experiment to test which type of fruit has the most enzyme activity per unit weight.
• Papain and bromelain are also the active ingredients in many meat tenderizers. Design an experiment to see if meat tenderizer can prevent gelatin from setting. Does the effect depend on how much tenderizer is added? Can meat tenderizer be denatured to neutralize the effect?
• Do research on alternative methods of protein denaturation, or other methods for inactivating enzymes. Choose one or more of these methods and see if it works on protein-digesting enzymes in fruit. (Don't eat the results of this experiment!)
• For other Science Buddies projects involving enzymes, see: Liver Stinks!, A Juicy Project: Extracting Apple Juice with Pectinase and Enzyme-Catalyzed Reactions -- What Affects Their Rates?.

• For more science project ideas in this area of science, see Cooking & Food Science Project Ideas.

Credits

Andrew Olson, PhD, Science Buddies

Sources

• Shields, R.K. (2003). Jell-o or Gel-no: Which Fruits Contain a Protein-Digesting Enzyme that Prevents Gelatin from Solidifying? California State Science Fair Abstract. Retrieved July 11, 2006, from http://www.usc.edu/CSSF/History/2003/Projects/J0411.pdf

Last edit date: 2010-01-26 23:00:00

Career Focus

If you like this project, you might enjoy exploring careers in Cooking & Food Science.

	Food Science Technician Good taste, texture, quality, and safety are all very important in the food industry. Food science technicians test and catalog the physical and chemical properties of food to help ensure these aspects.			Food Scientist or Technologist There is a fraction of the world's population that doesn't have enough to eat or doesn't have access to food that is nutritionally rich. Food scientists or technologists work to find new sources of food that have the right nutrition levels and that are safe for human consumption. In fact, our nation's food supply depends on food scientists and technologists that test and develop foods that meet and exceed government food safety standards. If you are interested in combining biology, chemistry, and the knowledge that you are helping people, then a career as a food scientist or technologist could be a great choice for you!
	Dietitian or Nutritionist Ever wondered who plans the school lunch, food for patients at a hospital, or the meals for athletes at the Olympics? The answer is dietitians and nutritionists! A dietitian or nutritionist's job is to supervise the planning and preparation of meals to ensure that people—like students, patients, and athletes—are getting the right foods to make them as healthy and as strong as possible. Some dietitians and nutritionists also work to educate people about good food choices so they can cook and eat their own healthy meals.

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