The grape juice and ripe quinces in this dish mean that this recipe only needs very little additional refined sugar.
Instead of light grape juice you can also use red grape juice, or even orange juice.
Mix sugar with1 cup of water in a saucepan and heat until the sugar has completely dissolved. Remove from heat and let cool. Peel the quince, rinse, quarter, core and bring to a boil in a pot along with the white wine. Cook until soft, 5-8 minutes. Puree with an immersion blender and mix with the sugar water.
Place in a chilled metal bowl and freeze for 3-4 hours. Stir occasionally with a fork to prevent the formation of large ice crystals. Alternatively, place mixture in an ice cream maker and freeze for 30-40 minutes. Scoop balls of sorbet and serve in dessert glasses.