A few nights ago, I threw down the towel. None of my modifications -- be it altering the amount of baking soda, or altering the combination of baking soda and vinegar -- produced results as tasty as the original, unaltered recipe for Hummingbird Bakery red velvet cupcakes. So I decided to face the truth and accept the fact that the sea-level recipe for Hummingbird red velvet cupcakes worked perfectly fine at high-altitude.
But like any true scientist, I decided to make the cupcakes again. Truth be told, I was checking for consistency -- I wasn't content to simply post the recipe online and declare it ready for high-altitude. So I rolled up my sleeves and followed the unaltered sea-level recipe, expecting the same results from last time -- ugly-topped, slightly bloated cupcakes with the perfect Hummingbird taste and texture:
But instead, these were my results (pardon the Tungsten lighting):
What?! These tops, although just a teeny bit bloated, were smooth. They were almost passable as those made at sea-level:
Why were these cupcakes so much smoother looking than my first batch?
I tried to remember what I had done differently during my initial control experiment and this time around. No new changes, or at least, not deliberate ones -- I'd even put the same amounts of batter (exactly 2 tablespoons) in the cupcake cases! If there was anything I'd done differently, it was that I'd speedily hastened through the baking process. In my impatience to see the results, I'd rushed through the creaming and mixing process to produce a final batter as quickly as I could...
Wait a second.
The Hummingbird Bakery advises to cream butter and sugar together for at least 5 minutes. Although they provide no rationale for doing so, it was something that I had picked up from a cursory read through of Paula Figoni's How Baking Works. Creaming is a way of adding air into batter; it is these air bubbles, along with those created by leaveners like baking soda, that rise up in the oven's heat and subsequently allow the cake's batter to rise up with it.
How Baking Works goes on to explain that these air bubbles get uniformly distributed during the mixing process. These air cells can be thought of as "seed cells" as steam and carbon dioxide gas move through these cells to enlarge them during the baking process. No new cells are formed during baking -- instead, steam and carbon dioxide fill and enlarge the existing seed cells. Without these air cells, there would be no leavening.
The number of air cells in the batter helps define the final baked good's crumb structure, and the number of air cells is defined by the mixing process. If you overmix the batter, you will create too many seed cells that will become overstretched, thin, and weak. During baking, these thin cell walls will stretch further -- bloating the baked good, possibly to the point of collapse.
Was it possible that I had overmixed my first batch? Was it possible that what I had considered diligent creaming only worked at sea-level and was overkill at high-altitude? While multiple air bubbles were a desirable outcome at sea-level, perhaps it wasn't the case here since air expanded faster at high-altitudes. Too many air bubbles expanding at a faster rate than normal could have resulted in the ugly, wrinkled tops of the first batch.