Why is it more difficult to make flaky pie crust using an electric mixing machine rather than one's own hands?

Making flaky pie crust is a delicate balance of technique and temperature. The correct answer addresses the important role that temperature plays in the outcome of the crust. When using an electric mixing machine, it can inadvertently heat the ingredients, particularly the fat, which is crucial for creating flakiness.

In pie crust, the goal is to keep the fat, such as butter or shortening, cold. When fat is cold, it will create distinct layers in the dough. This layering is what results in the desired flakiness after baking. An electric mixer can generate heat through friction, causing the fat to soften or melt too much before the crust is formed. If the fat is spread too thin and warmed, the result is a less flaky and more bread-like texture, as the structure of the dough changes.

While the other options mention aspects that can affect dough texture—like the need for more liquid, air incorporation, or the risk of over-mixing—these are less critical in the context of achieving the flaky texture specific to pie crust. The key issue with using an electric mixer is primarily related to the management of temperature during the mixing process, which is best controlled by hand mixing.