Why do Cupcakes sink in the middle?
One of the challenges of an amateur baker is making sure that their cake batter or dough rises just enough not for the cake to collapse. This incident of collapsing batter or dough mostly happens in the process of baking cupcakes. Three reasons can be attributed as to why your cupcake sinks.
First, it maybe because of over mixing the batter. Second, it may be due to having an over dose of the baking powder or baking soda in your mixture. Lastly, it is highly possibly and likely that you made a boo-boo and overfilled your cups.
When you over mix your batter, the tendency is for the batter to increase in gluten production which ends up with a heavy final product. If you were to bake bread, this occurrence would be fine. However, if you were working on making the perfect cupcakes, it is ideally best to combine all your ingredients with minimal mixing.
To support the second reason as to why cupcakes sink in the middle, baking powder or soda when used in excess causes small air pockets to evenly form around and through your dough as a result of the chemicals found in baking soda that has a carbon-dioxide reaction with the acidic elements in the formation. As an outcome of adding too much baking powder or soda, bubbles form and expand greatly in the batter which later breaks, causing your cupcake to sink in the center or in other words, collapse.
Lastly, all bakers know that cupcake dough, or pretty much all types of dough for that matter rises and expands when exposed to heat. Therefore, when cups are overfilled, the batter would not have anywhere else to go but level out in an overfilled baking pan.