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I put off exploring the science of cake for quite a while because I thought it would be boring. I've made basic chocolate cake more times than I could count (see photo for proof of previous chocolate cake experience), and while I hadn't ever delved into the detailed science of it, the process of cooking it seemed so dull and routine that I couldn't imagine the science being wildly different. So, in order to make the process more interesting I devised a chocolate cake experiment/competition. I decided to focus on the characteristic of my favorite cakes, the fluffy, light texture, and see how I could maximize that trait, and to what extremes I could go in terms of fluff.
In every experiment there are variables, so my first step was to identify the most common variables that may have an effect on a cakes fluffiness. Through research, I discovered some of these were baking soda/powder, eggs, and fats like milk and yogurt. I found a recipe that incorporated all of these ingredients to some degree, and got to work designing my experiment.
The Control Cake
The Control Cake
Cake #1 was the control. Every experiment needs a control in order to observe what would happen without intervention and make sure that the variables you chose actually have an effect that is different from the original. This is the recipe I used, it's not my favorite recipe ever, but it was simple enough and had fewer ingredients than many better recipes, that way it was easier to actually isolate variables. The control was surprisingly pretty fluffy to begin with. The outside texture was smooth with a few air bubbles. It had formed a bit of a hard crust in the oven.
A look at the inside of the control cake proved the presence of a moderate amount of air bubbles, many small ones and a few larger pockets. It tasted pretty good. The height of the control cake was 1/2 inch.
The Egg White Cake
The Egg White Cake
Egg whites, the key to a meringue's airy quality. But could the same technique be translated into a cake? For this layer I separated the egg whites from the yolks, adding the yolks in as normal, but beating the egg whites to stiff peaks before folding them in at the very end. As covered in the science of macarons page, egg whites are made up of a majority proteins. Quoting the science of macarons page on this blog "egg whites are 90% water, the other 10% is made up of proteins and small amounts of vitamins and minerals. But why use just the whites? Egg yolks contain fats that can ruin the meringue. Beating egg whites unroll, or denature, the amino acid chains that make up the whites. This is why, during the process of beating the egg yolks the mixture can triple in size and turns an opaque white. Hydrophobic amino acids in the egg whites coat air bubbles to protect them". Meaning, in the end, we should have way more air bubbles than any other mixture because we've essentially injected the cake with thousands of air bubbles.
This cake. Perfection. I love it. In a strange twist of events, despite tasting by far the fluffiest, it was not the tallest (but not the shortest!). The height of the egg white cake was just 3/4 inch. Just looking at the batter though, it's obvious this cake had the largest presence of air bubbles.
The Buttermilk Cake
The Buttermilk Cake
This was the variable I was the least sure about. There were minimal resources on the effect of buttermilk on baked goods, but a few promised a softer texture and an increased rise. From the science I knew already I saw the promise in buttermilk. Buttermilk is more acidic than regular milk, which, when combined with baking soda, produces carbon dioxide. Adding another acid to the mix meant I could add more baking soda, which needed equal parts acid to create a reaction. Buttermilk's high acid content also weakens the gluten networks formed by the flour in the cake, which gives the cake it's structure, leading to a crumblier cake.
The cake was in fact taller than the control cake, meaning buttermilk had in fact contributed to the rise. That being said, it crumbled immediately, making it impossible to cut or move. The inside also didn't differ greatly in visible air pockets from the control. The buttermilk also added a funkier flavor to the cake, which although somewhat distracting was not necessarily bad. The height of the buttermilk cake was 1 inch.
The Baking Powder Cake
The Baking Powder Cake
Lastly, the foolproof method to make baked goods rise more: baking powder. Why baking powder and not baking soda? Baking soda is made up of the base sodium bicarbonate and an acid that remains inactive until combined with water. Sodium bicarbonate needs an acid in order to react and form the carbon dioxide that gives baked goods their rise. Baking soda is only sodium bicarbonate, and requires an added acid like buttermilk. Therefore, while we can only use as much baking soda as we have acid, in theory there's no limit to how much baking powder we can use. I used around 3.5 times the baking powder the recipe called for, which is way more than you ever need.
The first thing I noticed about the baking powder cake was the texture of the top. I can't find much online as to why this cake looks so strange on top, but my very loose hypothesis has something to do with an imbalance in or absorption of moisture. You can really see the difference in outside texture when looking at this photo versus the buttermilk cake, which had no hard outer lining. The taste of the cake was pretty bad, as expected. A lot of baking powder with no added flavor to cover it up means a cake that tastes a lot like baking powder. It was the tallest cake by a bit though, standing at 1 1/4 inch.
Conclusion
Conclusion
Egg whites are the way to go. It won't be the tallest cake, but the texture is incredible and airy.
After the taste test I stacked my mutant cakes up to form a very sloppy layer cake (which was later split into two due to structural issues that I didn't care enough to fix).
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