For the blood orange marmalade, grate the peel of the two untreated oranges with a fine grater.
Fillet the grapefruit, oranges and blood oranges. To do this, cut a small cap on the blossom and stem. Place the fruit on one of the cut surfaces and thus cut the remaining peel with the white intermediate layer completely small.
Then remove the fillets from between the skins that separate the fruit segments. Put the peel, fillets and the collected juice in a saucepan.
When the weight of the contents of the pot reaches 1 1/2 kg, you can boil.
Pour in the sugar and bring to a boil, stirring throughout. Boil for one minute, then remove from the stove. When no more bubbles rise, stir in the whiskey.
Pour the blood orange marmalade into hot rinsed jam jars, close tightly and place on the lid for five minutes.