Spa treatment extends shelf life of 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, firms the flesh, delays browning and fading, slows wilting and increases 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 from 105 degrees to 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.
W. Wayt Gibbs, editor-in-chief of The Cooking Lab, is a contributing writer for the Associated Press.
Show commenting policy
TribLive commenting policy
You are solely responsible for your comments and by using TribLive.com you agree to our Terms of Service.
We moderate comments. Our goal is to provide substantive commentary for a general readership. By screening submissions, we provide a space where readers can share intelligent and informed commentary that enhances the quality of our news and information.
While most comments will be posted if they are on-topic and not abusive, moderating decisions are subjective. We will make them as carefully and consistently as we can. Because of the volume of reader comments, we cannot review individual moderation decisions with readers.
We value thoughtful comments representing a range of views that make their point quickly and politely. We make an effort to protect discussions from repeated comments either by the same reader or different readers.
We follow the same standards for taste as the daily newspaper. A few things we won't tolerate: personal attacks, obscenity, vulgarity, profanity (including expletives and letters followed by dashes), commercial promotion, impersonations, incoherence, proselytizing and SHOUTING. Don't include URLs to Web sites.
We do not edit comments. They are either approved or deleted. We reserve the right to edit a comment that is quoted or excerpted in an article. In this case, we may fix spelling and punctuation.
We welcome strong opinions and criticism of our work, but we don't want comments to become bogged down with discussions of our policies and we will moderate accordingly.
We appreciate it when readers and people quoted in articles or blog posts point out errors of fact or emphasis and will investigate all assertions. But these suggestions should be sent via e-mail. To avoid distracting other readers, we won't publish comments that suggest a correction. Instead, corrections will be made in a blog post or in an article.
- Steelers are banking on linebackers to improve strength of defense
- Medical personnel have plenty to do at Pittsburgh Marathon
- Kaboly: Steelers fill biggest needs by drafting defensive players
- Gorman: They ran for Erica who lived for the marathon
- Pirates suffer 3rd straight walk-off loss in St. Louis in 14 innings
- Motorcyclist killed in collision with car in Greenfield
- Proposed rule on noise limits for oil, gas sites in Pa. pleases none
- Pitt coach Narduzzi goes home for induction into Youngstown coaches hall of fame
- Kennywood to review park security, following fight
- Facebook still hangs onto teen users but is losing some of its luster
- LaBar: Looking at next big Diva star for WWE