On Food and Cooking

enzyme digests the gelatin molecules and
liquifies the jelly. But canned pineapple has
been heated enough to denature the enzyme,
and makes a firm gelatin jelly.
There’s a complication, though. The
reactivity of most chemicals increases with
increasing temperature. The rule of thumb is
that reactivity doubles with each rise of
20ºF/10ºC. The same tendency goes for
enzymes, up to a range in which they begin to
denature, become less effective, and finally
become completely inactive. This means that
cooking gives enzymes a chance to do their
damage more and more quickly as the
temperature rises, and only stops them once
they reach their denaturation temperature. In
general, the best rule is to heat foods as
rapidly as possible, thereby minimizing the
period during which the enzymes are at their
optimum temperatures, and to get them all the
way to the boiling point. Conversely,
desirable enzyme action — meat tenderizing,