swollen granules give a noticeable initial
graininess to sauces. However the granules are
fragile, and readily fragment into finer
particles; so having reached its thickest and
grainiest, the consistency of a potato-starch
sauce rapidly gets both finer and thinner.
Potato starch is also unusual for having a
large number of attached phosphate groups,
which carry a weak electric charge and cause
the starch chains to repel each other. This
repulsion helps keep the starch chains evenly
dispersed in a sauce, and contributes to the
thickness and clarity of the dispersion and its
low tendency to congeal into a gel on cooling.
Tapioca Tapioca, derived from the root of a
tropical plant known as manioc or cassava
(Manihot esculenta, p. 305), is a root starch
used mostly in puddings. It tends to form
unpleasantly stringy associations in water and
so is usually made into large pregelatinized
pearls (p. 578), which are then cooked only