Preserving faults

Mouldy jam results from damp fruit, insufficient boiling, poor storage, badly-filled or covered jars.

Crystallized jam indicates too much sugar in proportion to fruit or over-cooking jam to stiffen it when too little sugar has been used. Over-cooking and poor stirring resulting in undissolved sugar can also cause the problem.

Fermenting, ‘winey’ jam results from over-ripe fruit, insufficient sugar or boiling, poor covering and bad storage.

Hard, dry jam results from over-boiling or bad covering when jam is stored in a warm place. Plastic or screwtops will help to prevent this problem.