Halve the lemon and squeeze the juice. Wash quinces, rub thoroughly, quarter and remove the core. Cut quince quarters into small pieces, sprinkle with lemon juice. Peel 20 g ginger, cut into thin slices.
Put the ginger, quince and 1 litre of water in a large pot. Cover and cook for 30-40 minutes until the quinces are soft.
Line a sieve with a damp passing cloth or tea towel. Pour in the quinces and collect the juice. Quinces are best drained overnight. Save the quince meat for quince bread if necessary.
Peel the remaining ginger and cut into very small cubes. Pour quince juice into a measuring cup, if necessary fill up to 750 ml with apple juice. Bring juice, ginger and jam sugar to the boil in a wide high pot, simmer for about 5 minutes, skimming off the foam.
Pour jelly into clean, hot rinsed sealable jars, close immediately. Turn glasses upside down for approx. 10 minutes, then turn them over and let them cool down.