Found in a very wide variety of foods, gelatin is the gelling agent used to make gummy sweets, marshmallows, trifles and, of course, jellies. It’s also used as a thickener in ice cream, margarine, cottage cheese and more, and it helps to make low-cal meals taste less cardboardy.
The clear jelly you find in pork pies is a typical natural meat gelatin, although gelatin can be derived from a variety of sources – old-school examples include isinglass, from the swim bladders of fish (and used to clarify beers and wines), and hartshorn, made from the antlers of deer.
In the kitchen, gelatin can be found in sheets, which have to be soaked before use, or as an instant powder. Vegetarian alternatives include agar-agar, carrageenan and pectin.