Why don't my sponge cakes rise? The science behind baking a cake.

Karen Collins

I’m embarrassed to say my Victoria sponge cakes fall decidedly flat, even with my A -level in Home Economics. It turns out there are many possible reasons why I fail to get a rise, so how can I use science to improve my baking?

Perhaps my creaming technique is flawed? Correct creaming of the fat and sugar incorporates a lot of air into the mixture; it may seem obvious, but bubbles are essential for a light and fluffy texture. During creaming, bubbles form around the sugar crystals and become coated in a film of fat to form a foam. The fat shouldn’t be too cold or hard, and caster sugar is better as it has a larger surface area which means more bubbles. As I don’t have a manservant to complete this task for me, I have to resort to an electric whisk.

“But to stir butter and sugar is the hardest part of cake making. Have this done by a manservant. His strength will accomplish it in a short time.”

(Eliza Leslie, 1857)

Maybe the eggs are the wrong size? Eggs are vital to prevent the collapse of bubbles during baking; they also add liquid to the mixture. This liquid is mostly water, which turns to steam when cooking, inflating the bubbles further. Egg proteins form a layer around the air bubbles, coagulating when heated to form a protective layer. The eggs need to be the right size though, too much liquid and the cake mix may be too heavy to rise. 

Is it a problem with the flour and baking powder? The flour needs to be gently folded into the mixture, otherwise all the time spent creaming will be wasted as the air bubbles will burst. Baking powder contains sodium bicarbonate and a dry acid. When a liquid is added a chemical reaction occurs producing carbon dioxide gas and more bubbles. It’s important to cook the cake right away before these bubbles disappear. The rate of this reaction increases as the temperature increases in the oven. If there is too little raising agent, or it is out of date, there won’t be enough gas for a rise. 

Maybe my oven is too hot? Rising happens during the first two thirds of the baking time, this is followed by setting. If it is too hot then the outside will set before all the gas has expanded and the cake will not rise. Home ovens can be unreliable, I may need to buy a thermometer to check mine.

So there you go, the art and science of baking. Time to go and perfect my creaming technique and check the best before date of my baking powder!

For more information about baking science, listen to our episode about the Great British Bake Off.