defenses: when insects or microbes damage
its cells, the plant releases reactive phenolics
that attack the invaders’ own enzymes and
membranes. The brown pigments that we see
are essentially masses of spent weapons. (A
similar kind of enzyme acting on a similar
compound is responsible for the “browning”
of humans in the sun; here the pigment itself
is the protective agent.)
Minimizing Brown Discoloration Enzymatic
browning can be discouraged by several
means. The single handiest method for the
cook is to coat cut surfaces with lemon juice:
the browning enzymes work very slowly in
acidic conditions. Chilling the food below
about 40ºF/4ºC will also slow the enzymes
down somewhat, as will immersing the cut
pieces in cold water, which limits the
availability of oxygen. In the case of precut
lettuce for salads, enzyme activity and
browning can be reduced by immersing the