How does jello work?

Answer 1

Jell-O is composed of long, stick-like molecules. When you dissolve it in hot water, those molecules separate, but as the liquid cools, they begin to stick together like a giant heap of straws. The water flows slowly through these straws because of frictional effects. The result is a stiff material that is given its structure by the straw heap. If you leave the Jell-O long enough, the water will seep out and make puddles on the plate. So disgusting if you start to think about what is actually in it. Yup, jelly is made from cow or pig hooves, bones and connective tissue, all ground up and boiled. Yummy. The basic recipe for jelly is Gelatin, water, sugar, flavorings and food coloring. The gelatin is the important bit. Gelatin is basically a processed version of the protein collagen. You have probably heard of collagen before - this protein makes up a third of your body and is found in skin, bones and tendons, making them slightly elastic. As you get older, the collagen deteriorates and that's why our joints get stiffer and wrinkles start to appear in our once smooth skin. So how do they make gelatin from animal collagen? To start with, they grind up all the cow or pig parts and treat them with a strong acid or base. After this, it all gets boiled and the collagen is partly broken down. The gelatin can be skimmed off the surface of the liquid, dried into a powder and be used in jelly. As I mentioned, collagen is a protein. It is made up of long chains of amino acids, with every third amino acid being glycine. Lots of the other residues are proline or hydroproline. It lacks tryptophan, an essential amino acid that we can't make ourselves, so isn't a very good nutritionally source for humans, but who cares. So these long protein chains exist as a triple helix at room temperature- imagine this like three bits of spaghetti all twisted together. The chains in the helix are linked together by covalent bonds. When you make jelly, you add boiling water that provides the gelatin molecules with enough energy to break the bonds holding the chains together. Now, jelly is pretty amazing stuff as it is capable of holding around 10 times its own weight in water. This occurs because as the jelly cools down, the helices start to reform and cross linking occurs. The chains form areas of tangled protein with pockets between them- the water gets trapped in these pockets. This is what gives the jelly its characteristic wobble! What happens to gelatin when you add boiling water? The energy of the heated water is enough to break up the weak bonds holding the gelatin strands together. The helical structure falls apart, and you are left with free polypeptide chains floating about in solution.