Tunneling is a very common problem that affects home bakers, and if you frequently bake cupcakes, you’re bound to have experienced it at least one time. This term refers to open spaces that form inside of cupcakes. While they don’t affect the taste of the treats, if you’re baking for a special event and want truly perfect cupcakes to give to your guests, taking steps to avoid tunneling is important.
What’s tricky about tunneling is you usually can’t tell that it’s occurred until you eat the cupcakes. The problem can develop in just a few of the treats in a batch, and unless a guest shows you, you might not even be aware that it happened.
Tunnels develop in cupcakes due to an improper proportion of air in the batter. As cupcakes bake, chemical reactions between the ingredients cause bubbles to form and rise to the surface. This is what gives cake its flaky texture. If for some reason, the bubbles are unable to rise in a particular area inside of a cupcake, they will remain in place, leading to the formation of tunnels.
If you want to avoid tunneling, be sure to only mix your batter until the dry ingredients are no longer visible. Overmixing causes the batter to become too stiff and traps air bubbles in pockets. Also, be sure that your wrappers are completely centered inside of the tin before you fill them.