Kids, the ingredients list on a box of JELL-O® tells us that it is sweetened, flavored, and colored gelatin (take a look yourself). A box of strawberry JELL-O has sugar, gelatin, adipic acid (for tartness), artificial flavor, disodium phosphate and sodium citrate (to control acidity), fumaric acid (for tartness), and the dye red 40. Most of us like JELL-O, of course. But we bet that you will be quite surprised to learn that gelatin is essentially processed collagen, which is a structural protein in the connective tissue, skin, and bones of animals. Collagen also makes up about one-third of all the protein in the human body. Collagen is composed of the molecules glycine, proline, hydroxyproline, and other amino acids. JELL-O itself has little nutritional value apart from energy (80 calories per serving). Gelatin by itself is an incomplete nutritional protein because it lacks tryptophan, an essential amino acid.
Please note: All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.
Structurally, collagen is three polypeptide chains wound together into a helix, like three strands of spaghetti twisted together. When collagen is heated in water, the triple helix unwinds and the chains separate, becoming random coils that dissolve in water: this is gelatin. As the gelatin cools, the molecules try to regain the original helical structure and eventually bond together as they lose energy.
The way that gelatin molecules bond can trap large amounts of liquid, resulting in a semi-solid "colloid". All colloids have a disperse phase and a continuous phase; that is, one substance is dispersed throughout another substance. In JELL-O, the dispersed phase is the solid gelatin and the continuous phase is water. Gelatin can absorb a tremendous amount of water at up to 10 times its weight. Go ahead and make a box of JELL-O, following the package directions with an adult partner, and think about the chemistry going on with the molecules there.
Here is some trivia about JELL-O to amuse your family and friends:
- Gelatin is also in treats such as marshmallows and gummy candies. In the pharmaceutical industry, gelatin is used to make the outer shells for hard and soft capsules. A brand-new application is in the paint ball industry, which uses gelatin to make paint balls.
- As immigrants passed through Ellis Island, they were often served a bowl of JELL-O as a "Welcome to America" treat.
- When hooked up to an electroencephalograph machine (EEG), an instrument that records the electrical activity of the brain, JELL-O demonstrates movement that is virtually identical to the brain waves of a healthy adult.
- Fresh or frozen pineapple contains an enzyme that prevents JELL-O from setting; canned pineapple can be used because the canning process eliminates the enzyme.
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Kathleen Carrado Gregar, PhD, Argonne National Labs
[email protected]
October 2003
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References: C. Marasco, Chemical & Engineering News, 5-19-03, "What's That Stuff?"; http://web.kraftfoods.com/jello/main.aspx?s=&m=content_main (check out the "JELL-O 1-2-3" fun kids page here as well); "JELL-O: A Biography" by Carolyn Wyman (Harcourt, 2001); www.gelatin-gmia.com.
