Why do cakes shrink while hot?

1. Protein Coagulation: As cakes bake, the proteins in the batter, primarily gluten from the flour and albumen from the eggs, coagulate and form a network that traps gas cells. This network provides structure and shape to the cake. However, when the cake comes out of the oven and begins to cool, the protein network shrinks and tightens, causing the cake to pull inward and shrink.

2. Cooling and Evaporation: As the hot cake cools, moisture from the cake evaporates, leading to a loss of volume. This process further contributes to the cake's shrinkage.

3. Starch Retrogradation: Starch is a complex carbohydrate that gelatinizes during baking, absorbing water and contributing to the cake's texture. However, as the cake cools, the starch undergoes a process called retrogradation, where the starch molecules reassociate and form a more ordered structure. This rearrangement results in a reduction in the cake's volume and can also make it firmer.

4. Air Bubble Collapse: During baking, the heat expands air bubbles trapped in the batter, causing the cake to rise. However, as the cake cools, these air bubbles start to collapse, leading to a reduction in the cake's height and potential shrinkage.

5. Cake Density: Denser cakes tend to shrink more than lighter cakes. This is because denser cakes contain more ingredients, which means there is less air to expand and create a light and fluffy structure. As a result, denser cakes have less air to lose when cooling, leading to more significant shrinkage.

Minimizing cake shrinkage:

To reduce cake shrinkage, bakers can use various techniques, such as:

- Adding more leavening agents (baking powder or baking soda) to create a lighter and fluffier cake structure.

- Using cake flour, which has a lower protein content, resulting in less shrinkage.

- Avoiding overmixing the batter, as this can develop the gluten network too much, leading to more significant shrinkage.

- Cooling the cake slowly and evenly to prevent rapid evaporation and starch retrogradation.

By understanding and managing these factors, bakers can achieve cakes that maintain their shape and size after baking and cooling.