Shanne asks: I made this recipe (the banana blueberry version) but I substituted buttermilk for the milk. They ended up tasting like they had a horrible baking soda overload. I believe that I did not double the baking soda…of course, it is possible but I am generally careful about those things. Could the buttermilk have caused the baking soda to “over-react”? I made some other substitutions to the recipe but nothing “chemical” in nature. (Coconut oil instead of canola, brown rice flour instead of wheat, and ground flax/oat flour instead of oat bran.) I’ve made this recipe before and they were fine. Also, they “sunk” in the middle this time. It is so weird as I have never had this happen before in my baking. I’m very curious to know what caused this. If it was a momentary “brain cramp” then I know I have to be more careful in the future!
Thank you for your input!
Baking S.O.S. says: Substituting buttermilk for milk will definitely affect the chemical makeup of the muffin batter. Buttermilk is much more acidic than milk, so it reacts differently with the chemical leaveners in the recipe–the baking soda and baking powder. And when the chemical reaction is altered, it can create a metallic or bitter taste in your finished product. Also, altering the chemical reaction that causes the product to rise can also cause the product to sink in the middle once it comes out of the oven (as you said your muffins did).
Because buttermilk is acidic, it needs an alkaline leavener–specifically baking soda–to create the chemical reaction that makes a baked good rise.
Baking powder contains both acidic and alkaline ingredients to create chemical leavening all on its own–without any acidic ingredients needed in the recipe.
Since you introduced more acidity into the recipe with buttermilk, you should not need as much baking powder to make the muffins rise. (too much baking powder caused the metallic, bitter taste in this case)
The general rule of thumb for chemical leavening is: use about 1 tsp. of baking powder OR 1/4 tsp. of baking soda per 1 C. of flour in a recipe.
Good luck with the experimentation!