Mechanical Leavening

Mechanical leavening results when air is physically incorporated into a mixture and allowed to rise, or when steam in a mixture expands under heated conditions. When butter and sugar are mixed together during creaming, the sugar cuts into the butter and causes it to trap air. When egg foams are beaten, the protein in the eggs causes the air to be trapped, which is why they must be treated delicately to ensure that the foam retains the trapped air. Laminated doughs, such as puff pastry, are another example of a dough made using mechanical leavening, but instead of using trapped air from rising or creaming, pockets created by butter collect steam from the water in the dough. The steam begins to push the layers apart, creating the desired airy, flaky pastry.