pectin

Cranberries are high in pectin, a soluble starch that forms a gel and is used as a setting agent in making jams and jellies, which is why they thicken readily with minimal cooking.

The process also activates pectin, an acidic polysaccharide present in many fruits that sets the jam into a spreadable gel.

Farmhouses across the nation practically required at least one of the long-lived trees because of quinces’ natural pectin, an important gelling ingredient in preserves.

Sugar, pectin and a little lemon juice are the only other ingredients.

The fiber pectin is found mainly in an apple's pulp.