Drain juice from pineapple into small saucepan. Stir in pine-orange-banana juice and cornstarch, blend until smooth. Bring mixture to a boil over medium high heat and cook for three minutes, stirring constantly. Turn heat off and carefully move saucepan to a cool burner. Combine pineapple, banana, orange, and grapes in a mixing bowl. When mixture cools to room temperature, about 15 minutes, stir in fruit. Spoon over pancakes. Keep unused sauce refrigerated in an airtight container.
