To set, jams need the correct amount of pectin, sugar and acid. Pectin exists in varying quantities in all fruits, and can be drawn out by boiling. To get a good set using the boiling method it is necessary to boil the fruit for a long time. Some jams such as strawberry and cherry have to be boiled to such an extent that both the natural colour and flavourings are lost. By adding pectin the boiling time is cut down to 1 or 2 minutes, allowing the flavour and the colour of the fruit to remain unchanged.