2 cups fresh or frozen unsweetened blackberries, thawed, or one 16 1/2-oz. can blackberries , drained
1/3 to 1/2 cup sugar
1 tsp. unflavored gelatin
1/2 cup skim milk
1/4 cup water
1 (8-ounce) carton plain nonfat yogurt
1 tsp. to Tbsp. finely shredded orange peel
1/4 cup orange juice
Combine sugar and gelatin in a medium saucepan. Stir in milk and water. Heat until gelatin dissolves, stirring constantly, then remove from heat.
Place blackberries in a food processor or blender and process until smooth. Place in a sieve to strain out the seeds. Add the strained puree and remaining ingredients to the gelatin mixture. Pour into a 2 quart ice cream freezer and process according to manufacturers directions.