Gelatin by John Spottiswood.

Gelatin is flavorless and colorless, and if you dissolve it in a hot liquid, the liquid will gel as it cools. When reheated, say in your mouth, the gel melts. Most of us know gelatin as the key ingredient in the quivering dessert we call Jell-O®, but cooks also use it to make cheesecakes, mousses, marshmallows, meringues, chiffon pies, ice cream, nougats, aspics, and many other things. Gelatin will break down if exposed to the enzymes of certain raw fruits, like kiwi fruit, papayas, pineapple, peaches, mangos, guavas, and figs. Cooking these fruits, though, destroys the enzymes. If you plan to add these fruits to a gelatin salad, it's often easiest to buy them in cans, for all canned fruit is pre-cooked. Gelatin is made from the bones, skins, hooves, and connective tissue of animals, including pigs, so it's objectionable to vegetarians and members of certain religions. Kosher gelatins are available, and some of these are also vegetarian.