Pie crust is moist the day after cooking. Why?

When pie crust is moist the day after cooking, it is primarily due to retrogradation of the filling. Retrogradation occurs when gelatinized starches in the filling undergo a process of realignment as they cool, which can release moisture. This moisture can migrate to the crust, causing it to become soggy or moist.

The filling of a pie, especially if it contains significant amounts of starch, can contribute to this phenomenon. As the pie cools and sits, the moisture from the filling can permeate the crust, leading to texture changes that are undesirable.

This scenario highlights the importance of managing moisture levels in pie fillings and the timing of pie assembly to reduce the chances of a soggy crust. Properly blind-baking the crust or using techniques to stabilize the filling can help mitigate this issue, ensuring the crust maintains its desired texture.