Heat oven to 400 degrees. Grease bottoms only of 12 muffin cups or line with baking cups. In a medium bowl, combine flour, sugar, baking powder, cinnamon, and salt; mix well. In a small bowl, combine apple juice, oil, and egg; blend well. Add dry ingredients all at once; stir just until dry ingredients are moistened (batter will be lumpy.) Stir in chopped apples. Fill cups 2/3 full. Bake for 18-22 minutes or until toothpick inserted in center comes out clean. Cool 1 minute before removing from pan. Serve warm.