Leavening by Aeration

Aeration is the leavening action that occurs in pâte feuilletée when it bakes. It is a mechanical method that occurs in three ways:

1. Enclosed or trapped air: During the preparation of the puff pastry dough, a certain amount of air is trapped between each layer each time the dough is folded. During baking, these air cells expand and push the layers up and apart.
2. Steam: As pâte feuilletée is baked, steam is released from the melting butter and from the water contained in the dough layers. The steam created pushes on the leaves (layers) of dough, forcing them to rise. Concurrently, the starch contained in the flour coagulates on contact with the steam, strengthening the leaves of pastry and helping them remain separated.
3. Fat: As the fat (butter) held in the dough layers melts during baking, it leaves behind air pockets that can fill with steam and assist in the rising.