Why are the tops of my sponge cakes tough and cracking?

Question

My sponge cake has a layer on the top of the cake that is cracking and can be peeled off the cake. I have tried beating the mixture for a longer period.

Answer 1

The toughening and cracking of the top layer of your sponge cake is due to excessive moisture loss during baking. It's forming a 'crust' that can be easily peeled off due to the typically very weak soft crumb structure underneath.

There are multiple methods of reducing moisture loss you can implement alone or together:

• Check for doneness 5-10 minutes earlier in the baking process with the skewer method to avoid overbaking.
• Use a lower temperature for a longer time. If the initial temperature isn't high enough though, there won't be enough heat energy to generate steam in the batter for rising - try lowering 25F first if you can spare a batch.
• Use a hybrid high temp-low temp baking process - 400F then 250F. Most of the steam generation and batter rising will occur during the first third of baking, with the latter of the bake time spent dehydrating and setting the starches and proteins in the batter.
• If baking your sponge cake in a water bath, start with a higher bath temperature - boiling water straight from a kettle directly before putting in the cake batter - and check for doneness sooner as well.
• Add additional steam at the start of baking - preheat the oven with a sheet pan, then pour boiling hot water onto the sheet pan after the cake is in the oven and immediately before closing the door.
• Cover the top of the cake with a cut-to-fit sheet of parchment. The surface will trap a significant amount of moisture and may have visual imperfections when removing the parchment. If it's too wet, leave the cake in the oven a little longer.