1. Soften gelatin in water in a saucepan. Dissolve over low heat, stirring constantly. Pour gelatin into a large bowl and stir in milk.
2. Blend in grape juice concentrate, lemon juice, and sugar. Mix thoroughly.
3. Pour into metal pans, not more than three quarters full. Place in freezer until mushy. Turn into a chilled bowl and beat until fluffy. Return to metal pans and freeze until firm.