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Abstract Why are some fruits not recommended for adding to gelatin? Here is a basic science fair project for investigating enzymes that prevent gelatin from solidifying. It's an experiment with edible results!Objective The purpose of this science fair project is to determine if the enzymes in some fruits prevent gelatin from solidifying. Introduction If you like making gelatin for dessert, you might have noticed that the box recommends against adding certain kinds of fruit, such as pineapple, kiwi, mango, ginger root, papaya, figs, or guava. But why? What happens when you add these fruits to your gelatin? Why can you use some fruits, but not others? You’ll find out for yourself in this science fair project, but if you do a bit of background reading first, you’re likely to find that people have a hard time getting the gelatin to solidify when they add certain fruits. To discover why, you first need to know a little about what gelatin is and how it normally sets. Gelatin is a protein made from collagen. Proteins are a basic type of matter that make up all living things. Your skin, your blood, your hair—all of these are made up of many different types of proteins. One of those proteins is collagen. Collagen is a structural protein found in all animals, meaning that it helps give animals their structure, or shape. Collagen can be found in many parts of your body, including your skin, bones, muscles, and cartilage. Gelatin is a form of collagen that has undergone a chemical reaction to change it slightly and make it able to solidify when you're cooking with it. When you’re making a gelatin dessert, you dissolve the gelatin mix in water. The gelatin proteins are like microscopic (meaning too small to see with just your eyes) strands of spaghetti. These long, thin, flexible gelatin proteins tangle up with one another, the same way strands of cooked spaghetti do when they're all in one pot together. As the gelatin proteins tangle, they form mesh pockets that trap the water, sugar, and other flavoring agents that you’ve added to your dessert. The end result is a wiggly-jiggly solid to enjoy. Now, back to our original question. What happens when you add fruit to your gelatin? Some fruits, like strawberries, oranges, and apples, are a tasty addition; the gelatin solidifies around the chunks of fruit. But if you add fruits like pineapple, guava, mango, or kiwi, you end up with a runny mess that never solidifies. It turns out that this second group of fruits all contain proteases (pronounced PROH-tee-ay-siz), like papain (pronounced puh-PIE-uhn) and bromelain (pronounced BROH-muh-lin). Proteases are a special class of protein that act like a pair of scissors, cutting other proteins up. Could it be that the papain and bromelain in these fruits are cutting the gelatin protein into such small pieces that they are no longer able to tangle together and create a solid structure? This is exactly the question you’ll tackle in this science fair project. First you’ll see for yourself whether one of these protease-containing fruits interferes with gelatin’s ability to solidify. If it does, you’ll test whether it is the protease that interferes with solidifying by inactivating the protease (which means to make it stop working) in the fruit and then adding the fruit to the gelatin. You might be wondering how you will possibly inactivate the protease yourself. Remember that proteases, like papain and bromelain, are also proteins themselves. Most proteins can be inactivated using a variety of methods. One such method is called denaturation. Denaturation changes the structure, or shape, of the protein, without changing what it is made up of. Exposure to heat is one method of denaturing proteins. A good example of this process 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 proteases), denaturation of the protein causes an irreversible change. The heat will permanently inactivate the fruit’s protease. Does this allow the gelatin to solidify or not? Ready to find out? If so, get out your spoon, because with this science fair project, you'll get to enjoy some of your results as dessert! Terms, Concepts, and Questions to Start Background Research
Questions
Bibliography
Materials and Equipment
Experimental Procedure Caution: Preparing gelatin involves cutting with a knife, and pouring and stirring boiling hot water. Adult supervision or assistance is highly recommended. Project Overview
Testing the Different Gelatin Conditions
Variations
Credits Andrew Olson, PhD, Science Buddies Edited by Sandra Slutz, PhD, Science Buddies Sources This science fair project was inspired by the following:
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