If you have been baking for any length of time you probably noticed that when you store cakes and cupcakes the top crust gets soggy, sticky and/or moist. I have always been curious as to how this affected the rest of the cake, so I finally decided to satisfy my curiosity and test it out.
Before we dive into the results, let’s talk about what the crust is. In the latter stages of baking, evaporation of liquids from the surface of the cake slows down dramatically. Surface temperatures rise as evaporative cooling is taken out of the picture. Concentrations of sugar molecules left from the evaporation of the cake batter’s “syrup” then undergo caramelization and interact with protein molecules leading to browning Maillard reactions. The crust is composed of the dried, browned upper surface of the cake containing high concentrations of sugar molecules.
Because of sugar’s hygroscopic (water attracting) nature and the tendency for molecules to move from areas of high concentration to low concentration, water molecules from within the cake migrate to the crust leaving it sodden. My question was whether or not this internal moisture loss was noticeable or significant.
To test this I took a layer of Vanilla Bean Sour Cream Cake and split into two half circles. I then removed the skin from the top of one side of the cake, wrapped them both well and froze the cakes. After a couple of days, the halves were allowed to thaw fully wrapped for several hours at room temperature.
The cake which had the crust removed before it was wrapped had a bit softer, more moist crumb. The cake that did not have the crust previously removed was slightly more coarse and crumbly, as if it had staled a bit.
So, does it make a difference if you cut the upper crust from your cake before you store it? Yes. Are the differences significant enough to go through the hassle of taking the crust off? Probably not. Perhaps if you were baking for the queen or really wanted to impress someone with your baking skills it would be worth it. But as an everyday routine I would probably skip it.
There you have it. The crust on the top of your cake acts like a little sponge, absorbing liquids underneath. No need to worry though, your cake will be delicious whether or not you choose to remove the crust.