Reader Gail asks:
I have a question about altering recipes. I love buttermilk, I think it gives cakes a singular texture. So if I wanted to use buttermilk instead of regular milk in chemically-leavened layer cake batter, should I reduce the baking powder and add baking soda? Are there imbalances the buttermilk will cause? Or is it just not a good idea in general?
Interesting issues you raise here, Gail. One of the myths of baking is that recipes containing chemical leavening must be perfectly balanced from a pH standpoint. That’s not true much of the time. Sure, you don’t want heavy alkalinity in a batter that’s got a lot of fat or oil, since that gives you soap. But in general a little bit can be good since it gives you extra browning.
Likewise, a batter that’s acidic isn’t necessarily a problem. Acid adds tang and tenderizes, and also causes egg proteins to coagulate slightly before baking, which is handy if you have large inclusions in the batter (fruit pieces or chocolate chips) that you don’t want to sink before the batter bakes.
But you don’t know until you try…there is no magic pH for batter. So I’d say if you’re interested, go ahead and swap out the milk for buttermilk. It’ll probably turn out nicely…if a little more tender than normal. Adding soda would’t really do much except neutralize the buttermilk and thus rob you of the acid’s benefits (plus remember that baking soda is four times as strong as baking powder…a little goes a very long way).
If you’re worried about too much acidity, the better strategy is probably to cut the buttermilk with a little regular milk. A 50-50 mix of milk and buttermilk might be a good starting point if you want to experiment. Thanks for a great question!