With the emergence of Big Cupcake, almost all of us have seen some red velvet cake with white cream cheese frosting. And so let us delve into a little kitchen science, which may help us realize why our great grandparents' cake is not the same as ours.
Today, red velvet cake gets its coloring from a huge amount of red food coloring dumped in mix, staining the cake a vivid red, but it wasn't always so. Original red velvet cakes got the "velvet" part of their name not because they resembled bright red velvet dresses, but because their texture was so smooth and velvety. Their texture was, in part, influenced by the special ingredients put into the cake. Cake recipes varied, but almost all contained baking soda and either vinegar or buttermilk. Both buttermilk and vinegar are acidic, and anyone who has made a volcano in elementary school knows the copious bubbles that erupt when vinegar (or any acid) is mixed with baking soda. The bubbles fluffed up the cake, making it light and smooth.
The vinegar and buttermilk didn't just react with the baking soda. They also reacted with the cake's cocoa. Cocoa powder traditionally has anthocyanins; these are compounds that are also found in foods like red cabbage (which also features in many elementary school science projects). Red cabbage leaves can be used as pH indicators, getting redder in the presence of strong acids. It's the anthocyanins that change color in the cabbage, and they do the same in the cocoa, giving it a red finish.
But not anymore. Most of the cocoa powder on the market is processed with an alkalizing agent — a base. This neutralizes its acidity. It's the reason why a lot of recipes that use cocoa powder specify what kind of cocoa powder they take. The alkalizing agent will change the way the cake responds to baking soda or baking powder, so it will either fall flat or get too fluffy. The agent also darkens the powder, and keeps it from giving off a red tint when mixed with buttermilk or vinegar. So even if you got hold of an old recipe for red velvet cake, you probably wouldn't get the same results your cake-loving ancestors did.
(Then again, they might not even have gotten those results. Old recipes used to call brown sugar "red sugar," meaning they were lenient with the colors descriptions back then. The modern red velvet cake started during the Depression, as a relatively cheap way to make a cake look special and dramatic. So at least when you grab that red bottle, you've got a little history on your side.)
Image: Benson Kua.