Pectin (PEK-tin) is a mixture, not a compound. Mixtures
differ from compounds in a number of important ways. The
parts making up a mixture are not chemically combined with
each other, as they are in a compound. Also, mixtures have
no definite composition, but consist of varying amounts of
the substances from which they are formed.
Chemically, pectin is a polysaccharide, a very large molecule
made of many thousands of monosaccharide units joined
to each other in long, complex chains. Monosaccharides are
simple sugars. The most familiar monosaccharide is probably
glucose, the sugar from which the human body obtains
the energy it needs to grow and stay healthy. The monosaccharides
in pectin are different from and more complex than
glucose.
Pectin occurs naturally in many fruits and vegetables.
It is most abundant in citrus fruits such as lemons, oranges,
and grapefruits, which may consist of up to 30 percent pectin.
In pure form it is a yellowish-white powder with virtually no
odor and a slightly gummy taste. When dissolved in water, it
forms a thick, jelly-like mass. This property explains one of
its primary purposes: the jelling of fruits when they are made
into jams and jellies.
Pectin is made naturally in ripening fruit. It is obtained
commercially by treating the raw material (citrus peel or
apple pomace) with hot, acidified water. (Apple pomace is
the residue remaining after pressing of apples.) The pectin
in the peel or apple pomace dissolves in the hot water and is
then purified by repeated filtrations. It is extracted from the
water solution by adding alcohol or an aluminum salt to the
solution, causing the pectin to precipitate out of solution.
The precipitate is then dried and ground into a powder.
Additional steps are sometimes carried out to convert the
pectin produced by this method, called high ester pectin, to a
form that is more soluble: low ester pectin. To achieve this
