On Food and Cooking

thicken the sauce. If heated excessively, the
chains aggregate and coagulate in compact
clumps (right) that give the sauce a curdled
consistency and appearance.
Careful Temperature Control Cooks first
make the flavorful but thin liquid that will be
the bulk of the sauce and then add a source of
finely suspended proteins. An example is the
fricassee, in which the liquid is the stock in
which chicken or another meat has been
cooked, and the protein source is egg yolks.
The mixture is then heated gently. At the
point that the proteins unfold and begin to
tangle — but before they form strong bonds
— the sauce thickens noticeably: it clings to a
spoon rather than running off. The attentive
cook immediately takes the sauce from the
heat and stirs, thus preventing the proteins
from forming very many strong bonds, until
the sauce cools enough to prevent further
bonding. If the sauce gets too hot and the
proteins do form strong bonds, they clot