Pectin is a water-soluble fibre found in fruit and berries, acting as a natural gelling agent. It yields a gel that acts as a setting agent in jams, jellies and marmalades.
Fruits especially high in pectin are citrus fruits, apples, pears, quinces, rose-hips, lingonberries, cranberries, gooseberries, blackcurrants and red currants.
Strawberries, blueberries, cherries, peaches, apricots and rhubarb have a low pectin content.
Sometimes fruit or berries may be low in pectin on rainy summers when they have not had enough sunlight, or if they are overripe or underripe.
This, along with wrong proportions between water, sugar and acidity, may cause jellies and jams not to set, but to remain runny. In this case commercial pectin (E440) should be added to the jelly.
Commercial pectin is extracted from apple pulp, citrus peel, currants, lingonberries, etc.