When dealing with bran, corn meal, oat bran, wheat germ, etc. allow these grains to absorb the maximum volume of moisture. The best approach is to let the batter rest overnight in the refrigerator. The reward is a thicker batter, better flavor dispersal and higher caps. Muffins can be made with almost any liquid . Juices add flavor and tang, milk and other dairy products add sugar and fat which assist with browning and moistness.
Many bakers are partial to buttermilk in baking.
I love it for the flavor it imparts and its reaction with leaveners. Frequently, a recipe will instruct you to mix the baking soda with the buttermilk. I suggest you reserve the soda's leavening power and add it to the dry ingredients. Saco Buttermilk Powder should be added to dry ingredients. Baked goods which contain oil keep longer , but solid fats produce a lighter muffin since the batter takes in more air when the fat is creamed in.