On Food and Cooking

proteins that the cook works with. Nearly all
food proteins respond to the heat of cooking
by unfolding, bonding permanently to each
other, and coagulating into a firm, solid mass.
It turns out that gelatin molecules can’t easily
form permanent bonds with each other, due to
their particular chemical makeup. So heat
simply causes them to shake loose from the
weak, temporary bonds that hold them
together, and disperses them in water.
Because gelatin molecules are very long and
get tangled up with each other, they give the
mixture a definite body, and can even set it
into a solid gel (p. 605). However, gelatin is
relatively inefficient at thickening. Its
molecules are very flexible, while those of
starch and other carbohydrates are rigid and
better at interfering with the movement of
water and each other. This is one reason why
gelatin-thickened sauces are usually
augmented with starch. A sauce that contains
only gelatin requires a large concentration,