For the apple-grape sweetener: In a large saucepan, combine the apple and grape juice concentrates. Bring to a boil, reduce the heat slightly and cook at a low boil 15 to 20 minutes. Measure; you should have about 2 cups. Transfer to a jar and cool. Cover and refrigerate.
2.
For the pineapple sweetener: Pour the pineapple juice concentrate into a medium saucepan. Bring to a boil; reduce the heat slightly, and cook at a low boil 15 to 20 minutes. Measure; you should have about 1 cup. Transfer to a jar and cool. Cover and refrigerate.
3.
The sweeteners will have a 2-week shelf life in refrigeration.
