On Food and Cooking

Cloudy Suspensions: Thickening with
Particles Most of our raw ingredients —
vegetables, fruits, herbs, meats — are plant or
animal tissues built from microscopic cells
that are filled with watery fluids. The cells are
contained within walls, membranes, or thin
sheets of connective tissue. (Dry seeds and
spices contain no juices, but are still made up
of solid cells and cell walls.) When any of
these foods is broken apart into small pieces
by being ground in a mortar or pulverized in a
blender, they are turned inside out, so the
fluids form a continuous phase that contains
fragments of the solid cell walls and
connective tissue. These fragments obstruct
and bind the water molecules, and thus
thicken the consistency of the mixture. Such a
mixture of a fluid and solid particles is called
a suspension: the particles are suspended in
the fluid. Sauces made from pureed foods are
suspensions.
The texture of a suspension depends on the