The science behind chocolate cake

By Chef David “Smitty” Smith · 



Leavening agents
Oven temperature

I don’t get television at home, so I don’t watch any of the cooking shows and even when I did get TV, I only watched a few once in a great while. One of the few cooking shows I did like was “America’s Test Kitchen.”

When I am in the car, I usually have the radio set to the PBS station. Last winter, I would go to Reno once a week or every other week to shop and my timing became pretty standard. I would always go on Tuesday and I only realized it was pretty much the same time every week because I noticed I was always listening to “America’s Test Kitchen.” People call in with problems they are having with certain recipes or various cooking questions and the chef’s from the test kitchen would tell them what’s going on and how to fix it. I have to admit; I think I would like working in a kitchen like that sometimes as opposed to working on the line.

The last few weeks, I’ve gotten more questions than requests. I don’t have a commercial kitchen or the means to do endless experimenting to get the perfect answers to all the questions, but I do know how to go about figuring out a lot of them, which I have to say is fun and also has taught me a few things.

This week, I had the question of: “Why doesn’t my chocolate cake recipe work?” Once I saw the recipe, I could tell right away it wasn’t working because it wasn’t modified to take into account for the altitude. This recipe was a standard one and I knew what changes had to be made and why, but as I was checking on different cocoas, I learned something I had not realized. First, I’ll answer the original question.

“Why won’t a basic recipe work at high altitude?” The answer is air pressure. We learned back in school that water boils at 212 degrees. Well, at least that’s what we learned in Boston, at sea level. Because the air pressure is much lower at 6,200 feet, water boils at around 200 degrees.

What does that have to do with baking a cake? When water boils, it turns to its gaseous state and evaporates, meaning the water is not as hot so things take longer to cook.

When you bake a cake, you use leavening agents such as baking powder and baking soda to help the cake rise. As the leavening agents cook they turn to gas, expanding to help the rise. If you don’t change the recipe, the water will start to evaporate, the gases will expand too soon, and the cake will rise before the ingredients are fully cooked. The ingredients all need time to bond with each other so that they can thicken and hold together.

Although, maybe not totally technically correct, I like thinking about putting a book on a balloon and blowing the balloon up. As you pump more air into the balloon, you can see the walls of the balloon getting thinner. Too much air and it pops and the book falls back down to the counter.

When you cut into a cake, you will notice there are individual bubbles that make up the cake. Think of those bubbles are the cakes cells. The more pronounced the bubbles, the coarser the texture, which also can result in dry cake.

Another thing that often occurs is that when a cake falls it is because it has become dense and, again, dry. It is usually the cake that looks really smooth with no bubbles (they are so tiny and close together they don’t look like bubbles at all), and still has a nice spring to it when lightly pushed on, that is the moister cake. In other words, if the cells of the cake batter haven’t had a chance to bond and thicken before the water and leavening gases expand and evaporate, their walls get too thin and stretched and can blow up. This causes the cake to fall becoming dense and dry, or causing those bigger bubbles and a drier cake.

There are different ways of going about modifying various recipes and so there can be a trial and error period before you find your perfect cake. As with changing any recipe, whether baking or just cooking, start with small changes of just one or two certain ingredients at a time and see what happens. Another thing that you need to consider is that your oven and the temperature you cook at since everyone’s ovens are usually a little different.

That said, the basic rules are to decrease the leavening agents to take away a little of the expanding gases power. Also, because sugar will become more concentrated due to the evaporation rate of water, you want to decrease it. You know how sugar gets sticky and heavy when wet? Well, as the sugar gets too concentrated in the batter that also will weaken the cell walls keeping the other ingredients from fully bonding.

After decreasing those things, you will want to increase the liquid and possibly the flour. The last general rule is to increase the oven temperature by about 15 to 25 degrees so that the cake will start to set before the leavening gases can all expand.

You notice I always say general or basic rules because there might need to be some small adjustments made even from oven to oven. Next week, I’ll show you the changes I use in my chocolate cake and talk a little more about the different cocoas.


Smitty is a personal chef specializing in dinner parties, cooking classes and special events. Trained under Master Chef Anton Flory at Top Notch Resort in Stowe, Vt., Smitty is known for his creative use of fresh ingredients. He has been a chef for PGA’s Memorial Tournament for more than 15 years and ran the main kitchen at the World Games. For more information and archived copies of Stir it Up, visit Smitty welcomes questions and comments at [email protected], [email protected] or (530) 412-3598.




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Chef Smitty
Smitty is a personal chef specializing in dinner parties, cooking classes and special events. Trained under Master Chef Anton Flory at Top Notch Resort in Stowe, Vt., Smitty is known for his creative use of fresh ingredients. Smitty has been teaching skiing at Squaw Valley Alpine Meadows for more than 26 years each winter, and spends his summers working for High Sierra Waterski School since 2000. Smitty has been writing his chef column for Tahoe Weekly since 2005.