Mid-Baking: From Foam to Sponge

Appears in
On Food and Cooking

By Harold McGee

Published 2004

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Bread dough before and after baking. As the dough heats up, starch granules absorb moisture from the gluten, swell, and leak some starch molecules, creating reinforcement for the dough walls that surround the gas pockets.

Oven spring stops when the crust becomes firm and stiff enough to resist it, and when the interior of the loaf reaches 155–180°F/68–80°C, the temperature range in which the gluten proteins form strong cross-links with each other and the starch granules absorb water, swell, gelate, and amylose molecules leak out of the granules. Now the walls of the gas cells can no longer stretch to accommodate the rising pressure inside, so the pressure builds and eventually ruptures the walls, turning the structure of the loaf from a closed network of separate gas cells into an open network of communicating pores: from an aggregation of little balloons into a sponge through which gases can easily pass. (If the dough were not transformed into a sponge, then cooling would cause each isolated gas cell to shrink, and the loaf would collapse.)