On Food and Cooking

are so much smaller and lighter than intact
starch granules and cell fragments, they don’t
settle out and separate. And they are too small
and too widely separated to block the passage
of light rays: so unlike suspensions, molecular
dispersions are usually translucent and glassy-
looking. In general, the longer the molecule,
the better it is at obstructing water movement,
because long molecules more readily get
tangled up in each other. So a small quantity
of long amylose starch molecules will do the
same thickening job as a large quantity of
short amylopectin (p. 611), and long gelatin
molecules thicken more efficiently than short
ones. Thickening with molecules often
requires heat, either to liberate the molecules
from the larger structures — starch molecules
from their granules, gelatin molecules from
meat connective tissue — or to shake out
compactly folded molecules — egg proteins
— into their long, extended, tangly form.