Wash the untreated orange in hot water, dab dry and peel off the peel in fine strips. Halve the oranges, squeeze the juice. Measure out 80 ml. Select berries, wash. Weigh 900 g fruit flesh
Mix gelling powder and sugar in a large pot. Add berries, orange juice and zest. Bring to the boil while stirring over high heat. Boil for at least 3 minutes while stirring continuously. Immediately fill into prepared twist-off glasses and close them. Let cool upside down