What is physical leavening?

Physical leavening is a process in baking where air or steam is incorporated into a dough or batter to create volume and lightness in the final baked product. This can be achieved through techniques such as beating, whipping, or folding the ingredients to trap air bubbles, which expand during baking and cause the product to rise. Physical leavening is commonly used in recipes for cakes, muffins, and other baked goods that require a light and airy texture.

Physical leavening refers to the process of incorporating gas bubbles into a dough or batter to create volume and lightness. This is achieved through mechanical actions that trap air or release gases, resulting in a rise in the dough or batter. Common physical leavening agents include:

1. Aeration:
- Whipping: Beating ingredients rapidly to incorporate air bubbles, as in whipped egg whites or cream.
- Foaming: Dissolving proteins (e.g., albumin in egg whites) to create a stable foam that traps air.

2. Steam:
- Baking powder and baking soda: These chemical leavening agents release carbon dioxide when heated, creating steam bubbles that expand and leaven the dough.
- Boiling: Mixing ingredients with liquids that convert to steam during cooking (e.g., popovers).

3. Expansion of Gases:
- Yeast: A fungus that ferments sugars in the dough, releasing carbon dioxide as a byproduct. The gas bubbles expand and cause the dough to rise.
- Lactic acid bacteria: Certain types of bacteria produce lactic acid during fermentation, which reacts with baking soda to release carbon dioxide.