In large bowl, mix together bran, oat bran and buttermilk. Add oil, bananas, egg whites, and raisins. Sift together flour, baking powder, soda, and salt and add to batter. Carefully stir just until flour mixture is incorporated. Batter will be lumpy. Fill 18 paper lined muffin cups about 2/3 full. Bake in 400 degree oven for 20-25 minutes.