rich, creamy fluid. They’re mainly used to
thicken light-colored white sauces,
blanquettes, and fricassees. Yolk-thickened
sauces can be brought to the boil as long as
they’re also partly thickened by starch.
Sabayon sauces are also partly thickened
by the coagulation of yolk proteins(p. 639).
Liver Liver is a flavorful thickener, but has
the disadvantage of requiring disintegration
before it can be used. The coagulable proteins
are concentrated inside its cells, so the cook
must break the cells open by pounding the
tissue, and then strain away the particles of
connective tissue that hold the cells together.
Blood Blood is the traditional thickening
agent in coq au vin, the French rooster in wine
sauce, and in braises of game animals (civets).
It’s about 80% water and 17% protein, and
consists of two phases: the various cells,
including the red cells colored by hemoglobin,
and the fluid plasma in which the cells float.