On Food and Cooking

molecules are too small to do so, so
solutions are clear). •An emulsion is a
special kind of suspension, one in which
the dispersed substance is a liquid that
can’t mix evenly with the containing
liquid. Cream is an emulsion of butterfat
in water, and an oil-and-vinegar dressing
is usually an emulsion of vinegar in oil.
A gel is a dispersion of water in a solid:
the molecules of the solid form a sponge-
like network, and the pockets of water
are trapped in the network. Examples are
savory or sweet jellies made with gelatin,
and fruit jellies made with pectin.
A foam is a dispersion of gas bubbles in a
liquid or solid. Soufflés, bread, and the
head on a glass of beer are all foams.