Mash 3 bananas. Grate 1/2 tsp. of zest off an orange. Heat oven to 375. Coat a muffin pan with cooking spray. Whisk 1 large egg, 2 Tbsp fat-free sour cream, and 2 Tbsp buttermilk together in a bowl. In a separate bowl combine 1/2 cup oat bran, 1/3 cup whole wheat flour, 3/4 tsp. baking soda, 3/4 tsp. baking powder, and 1/4 tsp. salt. Stir 2 Tbsp. brown sugar into your banana mash. Stir into buttermilk mixture, then sprinkle in flour mixture and stir gently. Finally, fold in 1/2 cup blueberries and orange zest. Fill 6 muffin cups 3/4 full. Bake 15-20 minutes. They are done when a toothpick inserted in the center comes out clean.