Peel, slice and chop the ginger. Bring apple juice and ginger to the boil and simmer for about 4 minutes. Pour through a sieve. Measure the juice and if necessary fill up to 800 ml with apple juice.
Mix the jam sugar and apple-ginger juice well. Bring to the boil over a high heat while stirring continuously for at least 3 minutes until bubbly. Pour jelly into clean, well sealed jars (e.g. twist-off jars). Close them tightly with suitable lids, turn them over and let them stand on the lid for about 5 minutes.