On Food and Cooking

thicken (center). As cooking continues and the
temperature approaches the boil, the granules
swell even more and leak starch chains into
the liquid (right). It’s at this stage that the
sauce reaches its maximum thickness.
Cooling, Further Thickening, and
Congealing Once the starch in a sauce has
gelated, its amylose has leaked out, and the
cook judges the sauce to be properly cooked,
he stops the cooking, and the temperature of
the sauce begins to fall. As the mixture cools
down, the water and starch molecules move
with less and less energy, and at a certain
point the force of the temporary bonds among
them begins to hold the molecules together
longer than they are kept apart by random
collisions. Gradually, the longer amylose
molecules form stable bonds among
themselves, the kind of bonds that held them
together in the granule initially. Water
molecules settle in the pockets between starch
chains. As a result, the liquid mixture gets