Peel and quarter the pineapple and remove the hard stalk. Then cut into small cubes.
If the pineapple cubes weigh less than 500 g, balance with raspberries. There must be a total of 1 kg of fruit mass.
Put the pineapple cubes, raspberries and preserving sugar in a saucepan and bring to the boil while stirring. Let simmer for about 6 minutes while stirring. Make a gel test!
Finely chop the lemon balm and stir in.
Pour the jam boiling hot into clean glasses and close immediately.