Pec"tin (?), n. [Gr. &?; curdled, congealed, from &?; to make fast or stiff: cf. F. pectine.] (Chem.) One of a series of carbohydrates, commonly called vegetable jelly, found very widely distributed in the vegetable kingdom, especially in ripe fleshy fruits, as apples, cranberries, etc. It is extracted as variously colored, translucent substances, which are soluble in hot water but become viscous on cooling.

• A substance extracted from the cell walls of plants, especially of fruits; under acidic conditions it forms a gel. It is often used in processed foods, especially jellies and jams where it causes thickening (setting).
       Apple is rich in pectin and so is often added to other fruits when making jam so it will set.