1. Combine 1/2 cup grape juice and gelatin in a medium saucepan; cook over low heat, stirring until gelatin dissolves. Remove from heat; stir in 2 cups grape juice. Pour mixture into an 8-inch square baking pan. Freeze until almost firm.
2. Break frozen mixture into pieces, and place in a food processor; process several seconds or until fluffy but not thawed. Return to freezer, and freeze until firm.
3. Scoop sorbet into individual dessert dishes using an ice cream scoop. Garnish with mint sprigs, if desired.
carbo rating: 16