The fruits from which jams are made vary in their content of sugar, acid and pectin (a natural gum-like substance). All three of these make an essential contribution to the set and finished result. Generally speaking, fruits can be divided into three main categories:
- Fruits which are easy to make into a well set jam, e.g. apples, blackcurrants, damsons, gooseberries, plums, redcurrants.
- Fruits of medium setting quality, e.g. apricots, blackberries, raspberries and loganberries.
- Fruits of poor setting quality, e.g. cherries and strawberries.