Most people do not realize the crucial importance of freshness when
it comes to produce. In the same way that seeds gradually die,
fruits and vegetables go through a similar process as their
nutritional content gradually oxidizes or is broken down by the
vegetables own enzymes, but vegetables lose nutrition hundreds of
times more rapidly than cereals. Produce was recently part of a
living plant. It was connected to the vascular system of a plant and
with few exceptions, is not intended by nature to remain intact
after being cut. A lettuce or a zucchini was entirely alive at the
moment of harvest, but from that point, its cells begin to die. Even
if it is not yet attacked by bacteria, molds and fungi, its own
internal enzymes have begun breaking down its own substances.
Vegetables, especially leafy vegetables, are far more critical in
this respect than most ripe fruits. All, however, deteriorate much
like radioactive material; they have a sort of half-life. The
mineral content is stable, but in respect to the vitamins and
enzymes and other complex organic components, each time period or
"half life" results in the loss of half the nutrition. Suppose a
lettuce has a half life of 48 hours, two days after harvest only 50
percent of the original nutrition remains. After two more days, half
the remaining half is gone and only 25 percent is left. After two
more days half of that 25 percent is lost. Thus six days after
harvest and a lettuce contains only bout 12 percent of its original
nutrition. A two day half-life is only hypothetical. Those types of
produce I classify as very perishable probably do have a half-life
of from 36 to 48 hours. Moderately perishable produce has a half
life of about 72 hours; durable types of produce have half lives of
96 hours or longer.