Peel apples, cut into quarters and remove core. Puree apple peel and lemon balm and bring to the boil briefly together with the juice of the lemon and water.
Pour through a fine sieve into another saucepan and heat again together with the vinegar and sugar. Add the apples in turn and cook in two portions until translucent, pour into jars and fill with the hot broth. Close and store in a cool place.