On Food and Cooking

of the loaf reaches 155–180ºF/68–80ºC, 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.)