On Food and Cooking

Solid Dispersions: Jellies When the water
phase of a food fluid has enough thickening
molecules dissolved in it, and the fluid is left
undisturbed and allowed to cool, those
molecules can bond to each other and form a
loose but continuous tangle or network that
permeates the fluid, with the water
immobilized in pockets between the network
molecules. Such a network thickens the fluid
to the point that it becomes a very moist solid,
or a gel. It’s possible to make a solid — if
wobbly — jelly that is 99% water and just 1%
gelatin. If the gel is made from dissolved
molecules, then it will be translucent, like the
dispersion from which it is formed. Familiar
examples are savory jellies made from gelatin
and sweet jellies made from fruit pectin. If the
solution also contains particles — the remains
of starch granules, for example — then the
jelly will be opaque.