This past Monday, June 10, was my daughter Matilda’s 7th birthday. She’s been looking forward to this for a month or two, and working hard to ensure her birthday is everything she would love it to be. You know: detailed gift wish list, special dinner requests, treats for her classmates. And most notably, she emailed me the link to the chocolate cake recipe she wanted me to bake.
Now, not to reveal too much here, but I’m not really a baker. At least not an adventurous always-trying-new-recipes type of baker. I find the things I like to bake and a recipe I love and I stick to that. So far, chocolate cake isn’t one of those things. But you don’t say no to your daughter on her birthday, at least not where cake is involved. So, I gathered the ingredients and set about baking the cake. If you click through to the recipe, you’ll see that at the very last step before you pour the batter into the pans, you stir in a cup of boiling water. What? I’ve made cakes before, but I had never encountered this step. Why does the water need to be boiling? Let’s see if we can find out.
The first thing to note is that this recipe is made with cocoa powder, not baking chocolate. That turns out to be important. Cocoa powder is the dry powder made by grinding cocoa seeds and removing the cocoa butter from the dark, bitter, cocoa solids.
When cocoa powder is mixed with cold liquids, it remains in solid form, and you end up with a gritty mixture. When mixed with boiling liquids (some recipes for chocolate cake call for hot coffee), the cocoa powder dissolves and you have a smooth liquid. That seems pretty simple, right? Just a matter of reaching the melting point of the cocoa powder, allowing for the physical change from solid to liquid?
Yes, but it’s probably not that simple. It is reported that adding the boiling water to the batter also changes the flavor, releasing more of the deeper, richer chocolate flavor. This flavor enhancement seems to suggest that a chemical change is also occurring.
Cocoa powder contains both volatile and non-volatile components that contribute to the complex cocoa flavor. The non-volatile components include alkaloids, polyphenols, proteins and carbohydrates (shown below). Also, there are about 600 volatile components in cocoa that have been identified, including compounds of several chemical classes such as aldehydes, ketones, esters, alcohols, pyrazines, quinoxalines, furans, pyrones, lactones, pyrroles, and diketopiperazines.
These are the components that are responsible for the deep, complex flavor of cocoa. Does adding the boiling water to the batter allow for some chemical change in these components, thus deepening the flavor? The short answer is: I don’t know. But, after spending some time researching it this week, I’m not sure anyone else does, either. This would be a fascinating and delicious area to investigate further. And one thing is for sure, Matilda would volunteer to be the taste tester!