Preheat oven to 350 degrees F (175 degrees C). Spray muffin tins with non-stick cooking spray.
In large bowl, stir together flour, baking powder, soda, and salt.
In a medium bowl, beat egg whites slightly. Stir in bananas, sugar, oil, and lemon peel. Add to flour mixture, stirring just until combined. Stir in walnuts. Fill muffin pan cups 2/3 full.
Bake for about 20 to 25 minutes, or until tops are lightly browned. Remove muffins from pan.
