Mai Tai Sorbet

1/2 cup pineapple juice
1/2 cup peach-passion fruit nectar
1/2 cup guava nectar
6 tablespoons dark rum
1/4 cup sugar
4 teaspoons grenadine
1 tablespoon fresh lime juice
4 fresh pineapple wedges (optional)
Combine all ingredients except pineapple wedges in medium metal bowl and stir until sugar dissolves. Transfer sorbet mixture to ice cream maker and process according to manufacturer's instructions. Transfer sorbet to container; cover and freeze unit firm, about 2 hours. Freeze 4 Martini glasses for 1 hour. Scoop sorbet into frozen glasses. Garnish with pineapple, if desired, and serve.
Note: If you do not have an ice cream maker, you can turn this mixture into a granita - an Italian frozen dessert. Mix 1/2 cup water into sorbet mixture. Freeze in bowl until semi-firm, whisking occasionally, about 3 hours. Cover and freeze until solid, at least 6 hours or overnight. Using fork, scrape surface of granita to form crystals, scoop crystals into frozen glasses and serve immediately