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FOOD SCIENCE

Handling Fresh Fruits and Vegetables

By Fine Cooking Editors, editor

June 26th, 2013

By David Joachim and Andrew Schloss
from Fine Cooking #124, pp. 28-29

Ripe tomatoes, sweet corn, juicy berries-they're at their best right now, but their time is fleeting. How to make them last longer? What's the best way to prepare them? Such questions are pressing for any home cook at this time of year, so here, we'll discuss common ways of handling fresh produce, debunk the myths surrounding it, and bring truly helpful information to light. Along the way, you can test your own produce IQ with this quick true-or-false quiz.

TRUE OR FALSE: Removing the seeds from spicy chiles tames their heat.
FALSE. Capsaicins, the pungent compounds in chile peppers, are produced by the pepper's placenta, a spongy mass of flesh at the center of the pepper pod. The seeds are attached to the placenta, and sometimes the placenta ruptures, releasing small amounts of capsaicin onto the seeds. However, the lion's share of tongue-searing capsaicin resides in the placenta itself, which includes the ribs inside the pepper pod. So to take down the heat level of a chile, be sure to remove the ribs as well as the seeds.

TRUE OR FALSE: You should eat fresh corn as soon as you buy it.
TRUE. Shortly after fresh corn is cut from the stalk, its sugars begin converting to starch. Some varieties of sweet corn lose nearly 50 percent of their sweetness when left at room temperature for just a few hours. For the best results, buy corn that has been recently picked and keep it refrigerated until you cook it. Wait to shuck it until just before cooking, as the husks help retain moisture, keeping the corn juicy.

TRUE OR FALSE: Salting eggplant removes its bitterness.
MOSTLY FALSE. Modern purple globe eggplant has been bred to taste mild, so there's little bitterness to remove. But even for bitter varieties, salting doesn't remove bitter compounds so much as it suppresses them. This holds true for all bitter foods and drinks, from coffee to tonic water. Science has yet to fully explain the mechanics, but the sodium ions somehow disrupt our perception of bitter alkaloid compounds.

TRUE OR FALSE: Tomatoes should not be refrigerated.
TRUE. While refrigeration extends the shelf life of most fruits and vegetables, some produce, such as bananas and tomatoes, can succumb to what's known as chill injury. If ripe tomatoes are refrigerated they lose flavor, because sub-40°F temperatures cause the disappearance of cis-3-hexenal, a volatile flavor compound that gives tomatoes their signature aroma. For the most flavor and longest shelf life, store tomatoes between 50°F and 55°F, perhaps in a cool cellar or a wine refrigerator.

TRUE OR FALSE: Don't wash berries until you're ready to eat them.
TRUE AND FALSE. It's true that rinsing berries moistens them, and if left wet, the moisture can hasten mold growth during storage. That's why it's often recommended to wash berries just before eating them. However, briefly soaking berries in warm water can actually extend their life. This process is called thermotherapy. Various studies show that immersing whole strawberries, raspberries, and blackberries in 125°F water for 30 seconds helps prevent mold development. Blueberries can handle water up to 140°F. After immersing the berries, dry them gently with paper towels. Then refrigerate the berries at 35°F to 40°F for the longest shelf life.

TRUE OR FALSE: You can ripen underripe summer fruit in a paper bag.
FALSE. The paper bag method works only with fall and winter fruits that store starch, such as apples, pears, bananas, mangos, and kiwis. This starch is later converted to sugar when the fruit is exposed to ethylene, a hydrocarbon gas naturally emitted by plants. At home, you can increase the sweetness of these unripe fruits by putting them in a paper bag with a piece of already-ripe fruit that emits ethylene, such as a yellow banana. Summer fruits like peaches, plums, cherries and melons don't store starch, so they can't be made sweeter by exposure to ethylene after harvest. For the sweetest summer fruit, pick or buy it fully ripened.

TRUE OR FALSE: Asparagus is best cooked upright.
TRUE. Like all plant stems, asparagus stalks can be tough and fibrous. But the most prized parts of this vegetable, the delicate bracts clustered at the tip, are much more tender and easily overcooked. To cook the two parts of asparagus evenly, it's best to arrange the spears upright in boiling water so that the submerged stalks simmer in the water while the tips steam gently above its surface. You can buy special asparagus cookers for this purpose, but a tall, narrow pot works just as well.

TRUE OR FALSE: Tearing lettuce leaves by hand does less damage than cutting them with a knife.
FALSE. Some cooks recommend tearing salad greens with your fingers so that the leaves rip along natural junctures between the leaf fibers, thereby keeping the lettuce more intact. It turns out, though, that manhandling lettuce exacerbates the damage it purports to avoid, because of forceful squeezing and irregular stretching and tearing of leaf fibers. Cutting lettuce with a sharp knife blade does less damage to the leaves and keeps the leaf fibers more intact.

TRUE OR FALSE: Strawberries harbor more pesticide and herbicide residues than other fruits.
MOSTLY TRUE. Strawberries are always on the Dirty Dozen list of most contaminated produce, which is issued annually by The Environmental Working Group (ewg.org/foodnews), a consumer advocacy organization. In past years, tests have shown that strawberries harbor more pesticide and herbicide residues than any other fruit. But recently, apples and peaches have surpassed strawberries in total contaminant residues. Nonetheless, tests show that conventionally grown strawberries bear traces of 60 pesticides, so it's still advisable to eat organic strawberries (as well as the rest of the Dirty Dozen) whenever possible.

How does the crisper drawer work?
Fresh fruits and vegetables are crisp because their cells are packed with water; in fact, most produce consists of at least 70 percent water. For delicate lettuce leaves, losing as little as 5 percent of that moisture causes wilting. That's why baby salad greens so often turn limp.

The crisper drawer in your refrigerator is designed to retain moisture within fruits and vegetables. To achieve just the right amount of moisture in the air, crisper drawers are vented with levers or dials to adjust the humidity and air flow. For the crispest vegetables, especially leafy ones, keep the vent one-third to one-half open to ensure a humid environment yet allow some ventilation.

For crisp fruit, keep the vent closed to minimize the amount of oxygen that flows into the compartment. It may sound strange, but ripe fruit breathes on a cellular level. Plant cells take in oxygen and give off carbon dioxide. During the final stages of ripening, cell respiration increases by as much as five times, so closing the crisper vent slows down respiration and increases the storage life of the fruit.



posted in: Blogs, food science, fruit
Comments (9)

fireglowrose writes: Thanks for the info,it was an informative article. I had a problem though when I tried the warm water soaking with home grown raspberries. They went to mush.Maybe the bought ones are firmer.It worked great on saskatoons though! Posted: 9:09 pm on July 31st

RonBeau writes: Excellent piece. reading the item about refrigerated tomatoes losing their flavor (I already knew this fact) told me why my first 2013 gazpacho was so tasteless. I used refrigerated tomatoes, compared to my last batch which used tomatoes fresh from the garden. Duh??? Posted: 11:14 am on July 26th

RonBeau writes: Excellent piece. reading the item about refrigerated tomatoes losing their flavor (I already knew this fact) told me why my first 2013 gazpacho was so tasteless. I used refrigerated tomatoes, compared to my last batch which used tomatoes fresh from the garden. Duh??? Posted: 11:13 am on July 26th

AlexW writes: The author is not wrong:
Plants must use oxygen to convert stored carbohydrates into sugar to live. During the day, plants use carbon dioxide, water and sunlight to make carbohydrates, i.e. photosynthesis. This creates oxygen, some of which is used to turn the carbohydrates into sugar, to live, and the excess is released into the air.

At night, since there is no sunlight it cannot generate oxygen so it breathes oxygen from the air to convert stored carbs to sugars so it can continue to live to the next day. Posted: 12:36 pm on July 23rd

loop62 writes: That whole last paragraph is just plain wrong. We'd be in big trouble if it were true. Please check your "facts". Posted: 11:43 am on July 23rd

jetjones writes: Plants breath in carbon dioxide and give off oxygen. That's the basis of life on Earth, photosynthesis. Posted: 11:01 am on July 23rd

dianevaline writes: Terrific article I was wondering if there is further information about the handling of fresh herbs - mainly when to wash Posted: 9:45 am on July 23rd

K0EVE writes: This really helped me to clean up my act. Thanks for posting this. Posted: 6:43 am on July 23rd

Pomlover4 writes: This was so interesting and informative. Thanks for the information. I learned a lot. Posted: 5:37 am on July 23rd

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