Living in a citrus-growing area I've found out how much these fruits change once they're off the tree. Use the freshest fruit you can get your hands on. If you're fortunate enough to have a tree or know someone who does, pick the grapefruits when you're ready to squeeze the juice and make the sorbet. You'll have a great treat.
Combine the water and sugar in a small saucepan and bring it to a simmer over a medium flame. Stir until all the sugar is dissolved. Allow the syrup to cool, then chill it for at least 1 hour.
Combine the syrup with the grapefruit juice, 1 teaspoon of grenadine, 4 tablespoons of lemon juice, and the Pernod. Taste. Now add more lemon juice if needed?this will depend on the acidity of all the fruit. Remember, this sorbet should not be too sweet. Add more grenadine if you want it to be pinker.
Chill the mixture for 2 hours, then freeze it in an ice cream maker, according to manufacturer's instructions.
Recipe courtesy of Anna Thomas, The New Vegetarian Epicure, Knopf, 1996