In a small bowl, combine bran and buttermilk. Set aside to soak for 10 minutes.
Preheat oven to 350 degrees F (175 degrees C). Lightly grease muffin pan, or use paper liners.
In a large bowl, mix together flour, brown sugar and baking soda. Stir in bran mixture and egg whites. Fold in grated apple. Divide batter into 12 muffin cups.
Bake in preheated oven for 16 to 18 minutes, or until a toothpick inserted into the center comes out clean. Allow to cool for 5 minutes before removing from the pan.
