This
is a rather important understanding that goes against all our food
handling inclinations. Yet it is on hand and doable. One avoids
washing things off immediately because that encourages spoilage. Now
we merely soak instead in hot water. I wonder how lettuce performs.
I
note that it is useful to soak a cantaloupe a full hour in water
maintained at 120. that is a bit of a challenge and would only be
done if it was necessary. It would be easier to in fact cut it up
and process the pieces. Yet it illustrates the desirability of
actually reaching all the flesh in order to trigger all the changes
needed.
The
bottom line though is that this can clearly provide a week of ready
shelve life. This is good news as we always have partially consumed
product that needs to last a couple of days safely.
I do
enjoy eating an entire head of lettuce with dressing, but then I am
out of room for the rest of the meal. Thus unless I ensure others
consume the balance, I am soon facing ruination.
'Heat-shocking' can
help preserve produce
Nothing is more
frustrating than finding the perfect cucumber or head of lettuce at
the farmers market, paying top-dollar for it, and then … tossing it
out a week later when it has gone moldy or slimy in the refrigerator.
No doubt one reason so
many of us eat too many convenience foods and too few fruits and
vegetables is that it can be hard to get our busy schedules in sync
with the produce we bring home with the best of intentions. Food
scientists, however, have discovered a remarkably effective way to
extend the life of fresh-cut fruits and vegetables by days or even a
week. It doesn’t involve the chlorine solutions, irradiation or
peroxide baths sometimes used by produce packagers. And it’s easily
done in any home by anyone. This method, called heat-shocking, is 100
percent organic and uses just one ingredient that every cook has
handy — hot water.
You may already be
familiar with a related technique called blanching, a cooking method
in which food is briefly dunked in boiling or very hot water.
Blanching can extend the shelf life of broccoli and other plant
foods, and it effectively reduces contamination by germs on the
surface of the food. But blanching usually ruptures the cell walls of
plants, causing color and nutrients to leach out. It also robs
delicate produce of its raw taste.
Heat-shocking works
differently. When the water is warm but not scalding — temperatures
ranging from 105 degrees to 140 degrees work well for most fruits and
vegetables — a brief plunge won’t rupture the cells. Rather, the
right amount of heat alters the biochemistry of the tissue in ways
that, for many kinds of produce, firm the flesh, delay browning and
fading, slow wilting, and increase mold resistance.
A long list of
scientific studies published during the past 15 years report success
using heat-shocking to firm potatoes, tomatoes, carrots, and
strawberries; to preserve the color of asparagus, broccoli, green
beans, kiwi fruits, celery, and lettuce; to fend off overripe flavors
in cantaloupe and other melons; and to generally add to the longevity
of grapes, plums, bean sprouts and peaches, among others.
The optimum time and
temperature combination for the quick dip seems to depend on many
factors, but the procedure is quite simple.
Just let the water run
from your tap until it gets hot, then fill a large pot of water about
two-thirds full, and use a thermometer to measure the temperature. It
will probably be between 105 degrees and 140 degrees; if not, a few
minutes on the stove should do the trick. Submerge the produce and
hold it there for several minutes (the hotter the water, the less
time is needed), then drain, dry and refrigerate as you normally
would.
Researchers still are
working out the details of how heat-shocking works, but it appears to
change the food in several ways at once. Many of the fruits and
vegetables you bring home from the store are still alive and
respiring; the quick heat treatment tends to slow the rate at which
they respire and produce ethylene, a gas that plays a crucial role in
the ripening of many kinds of produce. In leafy greens, the shock of
the hot water also seems to turn down production of enzymes that
cause browning around wounded leaves, and to turn up the production
of heat-shock proteins, which can have preservative effects.
For the home cook, the
inner workings don’t really matter. The bottom line is that soaking
your produce in hot water for a few minutes after you unpack it makes
it cheaper and more nutritious because more fruits and veggies will
end up in your family rather than in the trash.
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