On Food and Cooking

it’s the most abundant plant product on earth.
Like starch, cellulose consists of a chain of
glucose sugar molecules. But a difference in
the way they’re linked to each other allows
neighboring chains to bond tightly together
into fibers that are invulnerable to human
digestive enzymes and all but extreme heat or
chemical treatment. Cellulose becomes most
visible to us in the winter as hay, a stubble
field, or the fine skeletons of weeds. This
remarkable stability makes cellulose valuable
to long-lived trees and to the human species
as well. Wood is one-third cellulose, and
cotton and linen fibers are almost pure
cellulose. However, cellulose is a problem for
the cook: it simply can’t be softened by
normal kitchen techniques. Sometimes, as in
the gritty “stone cells” of pears, quince, and
guava, this is a relatively minor distraction.
But when it’s concentrated to provide
structural support in stems and stalks — in
celery and cardoons, for example — cellulose