Gelatine is a versatile gelling agent made from 85% collagen, a protein found in animal connective tissue and bone, hence the reason gelatine is not suitable for vegetarians. The same process in preparing a stock, the slow simmering of bones was used in Victorian kitchens for calf’s foot jelly which was then clarified and flavoured. Today’s commercial manufactured gelatine is often made from pork bones so be careful of any dietary restrictions. As home cooks the most commonly available form of gelatine is sachets of dried powder or granules. Leaf gelatine is used by most commercial chefs because it generally results in a smooth, clearer consistency and comes in three quality grades bronze, silver, and gold. Three teaspoons of powdered gelatine, eight grams or one sachet is roughly equivalent to four gelatine leaves. Unprepared gelatine has an indefinite shelf-life as long as it is wrapped airtight and stored in a cool, dry place.
There are a few top tips to remember when using gelatine and its ability to act as a setting agent. The general firmness of the jelly relies on the ratio of water or fruit juice to gelatine so carefully follow the manufacturers instructions. Do not add fresh or frozen pineapple to gelatine or jelly, along with raw figs, kiwi fruit, guava, ginger root, and papaya as they contain an enzyme called bromelain which breaks down gelatine causing it to lose its thickening properties. The enzyme is deactivated by cooking, so canned pineapple and kiwi are fine to use. The more sugar in the recipe, the softer the resultant gelatine will be.
Ps. In America jelly is something you spread on toast or bread ( English jam ) and the wobbly dessert is named after a proprietary brand Jell-O.