Do you think of apples, peaches, cucumbers and red peppers as inert, lifeless objects? Take a closer look at the magical inner workings of fruits and vegetables, and you’ll never see them quite the same way again.
They’re prone to bumps and bruises, they’re sensitive and picky, and they crave TLC. No, we’re not talking about touchy toddlers; we’re talking about fruits and vegetables — living, breathing entities that, as it turns out, are nearly as vital and complex as we are. They have quirks and quibbles, preferences and personalities. They have circadian rhythms, they bruise when mishandled and pant in the heat. Much like people, each has a complex internal chemistry and a limited lifespan. And by the time most fruits and vegetables make their produce aisle debut, they’re in the twilight of their lives.
“People need to understand that fruits and vegetables are not manufactured, static items,” says Russ Parsons, the food editor and columnist for the Los Angeles Times and author of How to Pick a Peach: The Search for Flavor from Farm to Table (Houghton Mifflin, 2008). “They develop and adapt and age just like the rest of us.”
How fruits and veggies live — how they are raised and nurtured and handled — dramatically affects the flavor and nutrients we can hope to reap from them. Here’s a glimpse into some of their mysterious inner workings. Chances are, you have more in common with the contents of your crisper than you think.
Living, Breathing, Choosing, Responding
At every stage of their existence — from conception, maturity and ripening, to shipping, retailing and composting — fruits and vegetables are undergoing myriad and magical biological and chemical processes in response to their environments.
As Peter Tompkins and Christopher Bird report in their 1973 classic, The Secret Life of Plants, “Plants move their bodies as freely, easily and gracefully as the most skilled animal or human, and . . . the only reason we don’t appreciate the fact is that plants do so at a much slower pace than humans.” Plants, they add, “are capable of intent: They can stretch toward, or seek out, what they want in ways as mysterious as the most fantastic creations of romance.”
Indeed, fruits and vegetables constantly make choices that determine what they will become. Left to their own devices, for example, plants will do everything in their power to satisfy their basic need for sun and water — following the sun with their branches, tilting their leaves to catch light or water, and pushing their roots down and out into the soil in search of nutrients.
And it doesn’t stop there. Plants react to everything, including the wind, temperature, soil and stars, says Gunther Hauk, a biodynamic farmer in Illinois and author of Toward Saving the Honeybee (Rudolph Steiner Press, 2003). For instance, Hauk has found that seeds sown three days before a full moon have a much higher germination rate than seeds sown three days before a new moon. For this he credits the moon’s fertility. It may sound a little woo-woo until you consider that just as the moon exerts a tidal pull on water in the ocean, it also affects the water and waterborne nutrients stored in the soil and in plants’ bodies. So it makes sense that the level of soil-stored nutrients available to a plant at a given time is directly related to the stage of the lunar cycle, and that plants respond accordingly. (For more on the intimate relationship between plants and the soil in which they’re grown, see “Good Earth” in the October 2008 archives.)
Complex Biological Entities
All plants have meristematic cells that are much like the stem cells in people, says Preston Andrews, PhD, professor of horticulture at Washington State University in Pullman, Wash. Meristematic cells, found in meristem tissue, are undifferentiated, meaning they can morph into flowers, fruits, roots or whatever the plant may need. “When you remove a tip or shoot you remove that meristem tissue, so the plant responds by replacing what was taken,” explains Andrews.
Plants also have skeletons, made of cellulose instead of bone. Cellulose is Mother Nature’s modeling clay. It takes any form she dreams up, from the bell-shaped flesh of a red pepper to a crunchy stalk of celery. Cellulose has a hollow, matrix-like structure that’s both strong and flexible. Its strength helps it resist hailstorms and wind gusts. Its honeycombed walls protect the delicate fluid-filled vacuoles within. Like nutrient-rich piñatas, these vacuoles hold the secret ingredients to each individual fruit’s flavor and aroma.
But plants are much more than just cellulose and water. Floating within each cell is a brew of compounds that lends fruits and veggies everything from flavor, smell and color to antioxidants and phytonutrients. One of the most important is chlorophyll, the chemical that makes plants green. Responsible for absorbing sunlight for photosynthesis, the chemical constituents of chlorophyll are similar to the heme structure of hemoglobin in human blood. And once ingested by humans, they act as powerful detoxifiers of our blood and tissues.
Not unlike humans, edible plants owe their aging, or ripening, to a surge of hormones. But, rather than depending on testosterone and estrogen, plants rely on ethylene to come of age. A powerful plant hormone, ethylene triggers cell walls — once rigid with cellulose — to soften, and it also dissolves pectin, the glue holding plant cells together. Once broken down in this way, the pliable and permeable cell walls invite the mingling of compounds that create a fruit’s juice as well as soften its skin.
Inside a ripening fruit, the complexity of flavor increases. Its flesh naturally sweetens as simple sugars (glucose) morph into more complex versions of themselves (fructose and sucrose). “Ripeness is not a fixed point, but a process,” says Parsons. “It begins with pollinated flowers forming fruit, and it ends with rot.” That’s why being sensitive to a plant’s lifecycle can help you take advantage of fruits’ peak moments of taste and nutrition — and avoid a soggy, fly-infested fruit bowl.
Vegetables ripen in a slower, more controlled, manner. Thanks to their slowpoke ways, they also live longer. And, unlike fruit, their flavor (and many times their smell) is released only when their cells are crushed (or collapsed during cooking). “You have to break the cells to get the nutrient value out,” says Stephen Goff, PhD, a plant biologist at the University of Arizona, Tucson. The necessary destruction allows for neighboring enzymes to cohabitate in new ways. For instance, what’s more boring than an onion?But cut one open and a dizzying array of chemical reactions takes place — some of which can literally bring tears to a cook’s eyes.
Ushering vegetables into maturity is relatively straightforward, but ripening fruits is tricky business. Some fruits, like berries and cherries, refuse to ripen at all once they are removed from their parent plants. Others, like tomatoes and pears, are happy to be plucked green and need nothing more than a sunny windowsill to divulge their innermost secrets.
This fickleness is a formidable hurdle for growers who want to get their produce to consumers at the height of flavor. Some producers actually blast their fruit with ethylene gas at the warehouse to force it to ripen on demand. But, while ripening with ethylene gas will cause fruit to soften and change color, it can’t add sugar or any of the other chemicals that add up to a complex flavor, explains Parsons. “Picked at just the right moment and ripened this way, a tomato can be adequate, but it will never be great.”
You can, however, use ethylene gas at home to gently speed the ripening process with good results. Try it with pears, which you can safely buy green and bring to perfection on the countertop. If you’re in a hurry, place a few pears in a paper bag and fold the top down. The bag traps the fruit’s ethylene gas and accelerates ripening.
To avoid accidentally speeding ripening (and rotting), separate ethylene-producing fruit, like apples and avocados, from non-ethylene-producing fruit and vegetables, like bananas and leafy greens. (For more fruit and vegetable storage tips, see “Fruit-Bowl Wisdom,” in the related content.)
Sensitive and Vulnerable to Bruising
Harvesting delicate fruit without damaging it is hard enough; add a cross-country trek to the mix and the challenges multiply. Like human skin, plant skin is vulnerable to infection. The smallest nick or puncture wound on the surface can become a festering sore. Yeasts and molds lurking on the surface speed to the cut to feast on whatever juices, sugars and organic acids leak out.
Cuts can also lead to enzymatic browning. Most produce — especially apples, pears, bananas and artichokes — contains substances that, when exposed to oxygen, change the color of the flesh to brown. The browning itself doesn’t affect the taste or nutrients so much as appearance, but few people would choose brown-tinged fruit over a fresh-fleshed sibling — in part because we’ve come to associate browning with other types of damage (such as bruising, molding and fermenting), which do affect taste.
But surface nicks aren’t a fruit’s only worry. Just as human tissues bruise when manhandled, too much pressure can bruise delicate produce, squashing cell walls and sending fluids flooding into damaged tissue. Unlike people, though, produce can’t repair the damage. Instead, a bad bruise simultaneously accelerates both ripening and dehydration, which can lead to premature death. One bad bruise quadruples the rate at which apples lose water.
Even the vibrations created by trucking produce cross-country can cause problems. Vine-ripened tomatoes, for instance, must be carefully packaged to ensure the gel around the seeds isn’t shaken to the point that it falls right out of the fruit the moment it’s cut, says James Gorny, PhD, executive director of the Postharvest Technology Research and Information Center at the University of California at Davis. In fact, he notes that upward of 25 percent of all fruits and vegetables picked in the United States are never eaten because they are lost to such damage.
But rough handling doesn’t just make for less attractive produce, it also lowers the nutrient content of certain fruits. Vitamin C is especially vulnerable. Because a bruise damages cellular and tissue structure, it can also disrupt a fruit’s delicate chemical balance. For instance, a bruised tomato quickly loses roughly 15 percent of its vitamin C.
Flexible Rate of Aging
With their delicate hormones, skin and water needs, it’s no wonder that fruits and veggies must be raced to market. “Most fruits are never going to be any better than the first day you pick them off the vine,” says Gorny. “There is nothing we can do to enhance quality — it’s all about preventing decay.” As a result, skilled handlers have developed several tricks to fool fruit into aging gracefully.
One way is to keep them cool. Like people, fruits and vegetables need to breathe. But their breathing rate is linked to temperature. When they get hot or physically taxed, they “pant,” increasing their rate of respiration and gas exchange much as we do when overheated. Similarly, fruits’ and veggies’ breathing slows as they cool down.
That’s a good thing, because as they breathe, they use energy, just like us. Unlike us, however, they can’t reach for a snack to replenish low energy stores; instead they are forced to break down their complex parts (starch, sugars and organic acids) into simpler molecules, and those parts are what gives them their flavor.
Essentially, the less fruits and veggies breathe, the more flavor they retain. (Interestingly, not all produce breathes at the same rate: Asparagus, broccoli, mushrooms and peas breathe 10 times faster than apples, cabbage, lemons and tomatoes.)
Take care in how much you restrict respiration, though: Chill a fruit too much and you’ll destroy enzymes necessary for ripening. “If you’ve ever bitten into a mealy, dry peach, it’s because something went wrong during ripening, storage or transport,” says Gorny. “Most likely the enzymes involved in the softening process, which results in sweeter, juicier fruit, were broken by exposure to too-cold temperatures.”
Temperature also tells a plant when to turn starch into sugar. A plant’s starch is like a person’s stored fat — energy saved for a rainy day. Similarly, plant sugar is like ours in that it’s used as quick fuel. Vegetables are typically higher in starch (think potatoes, carrots and beets), but cooking them softens their structure and invites a sweetness that comes more naturally to fruit.
As fruits ripen, enzymes turn starch into sugar. Bananas are a perfect example. At cool temperatures, they stay green. If you’ve ever bitten into a green banana, it tastes starchy. But when bananas are left on the countertop to ripen, not only is the starch converted to sugar but the chlorophyll also breaks down to reveal the fruit’s underlying bright yellow jacket. “It’s a complex chemical ballet,” says Gorny. Get a banana at just the right moment and you enjoy a lovely array of floral aromas and a firm, creamy texture. Wait too long, of course, and you end up with a bland, grayish mush.
A similar type of starch-sugar conversion happens in potatoes, with different but equally dramatic consequences. Chill potatoes and they convert some of their starch to sugar. “That’s fine if you want them sweet,” Gorny says, “but try to make French fries out of them and that excess sugar turns them either black or brown.” Which is why potatoes are best stored in a cool and dark, but not cold, location.
Responsive to Nature and Nurture
The breeding and developmental environment a farmer gives a plant can make an immense difference in its quality, but so can the TLC it receives long past the harvest.
Just as children can’t escape the influence of their acquaintances and educators, a fruit’s or vegetable’s personality — measured by its depth of flavor and breadth of nutrients — is shaped by the caring hands of subsequent handlers. And that includes everyone from the produce manager and baggers at your market to you and anyone else who handles your food at home.
“The baggers at the store think I’m a fussy person for insisting they treat my produce gently,” says Lynn Gordon, founder of French Meadow Bakery and Café in Minneapolis, “but it’s easy to bruise, and therefore I treat it lovingly all the way to my refrigerator and beyond.”
When traveling between the store and home, Gordon gives her fresh produce the same care and attention she gives her fragile eggs. And when she’s preparing a meal at home or at her restaurant, Gordon takes special steps to honor the complexity of the fruits and vegetables she’s about to turn into food. She makes sure to have plenty of beautiful bowls and colanders on hand to receive the fresh produce. She keeps her kitchen spotless, her knives sharp, and she makes sure she’s feeling relaxed as she cooks to keep the food’s energy from becoming contaminated by stress.
“Every step, from the field to the plate, should have an energy of reverence, acknowledgement and consciousness,” says Gordon. “That’s what makes good cooking great.”
When so much of the food we buy is packaged in cardboard and plastic, it can be easy to forget much of it originally came from living plants. (Try emptying a package of instant oatmeal into a bowl and visualizing the graceful stalks of grain that gave way to the powdery pile. It’s a stretch.)
Still, while so much of what’s found in the grocery store is the food equivalent of the morgue, the produce aisle is nature’s reminder that food is synonymous with life. Take one look at its bright red apples or chubby purplish-black eggplants, and the magical transformation of energy from sun to plants to people is undeniable.
Whether you appreciate produce for the long path it has traveled, for the amazing and complex science it represents, for the consciousness it embodies, or simply for the nutritious and delicious eating experience it delivers, once you understand what the lifecycle of edible plants involves, it’s tough to look at fruits and vegetables without at least a little newfound respect.
How to properly store fruits and veggies at home.
By the time fruits and veggies make it to your kitchen, they’re pretty much in the twilight of their lives, so it’s very important to store them properly. Some fruits and vegetables are safe to refrigerate; others should be stored on the countertop to protect the delicate ripening enzymes. Whether they’re stored in the fridge or on the counter, remember to keep ethylene producers (see Web Extra! at the top right of this page) away from ripe fruits and mature vegetables so you don’t accelerate aging. And, since moisture speeds decay, don’t wash fruits and vegetables until you’re ready to eat them. Put paper towels between layers of berries to extend storage time. Get more tips in “Handle With Care” in the May 2005 archives.
Store at room temperature — on the counter, in the pantry or in a drawer — and use while fresh.
Apples (less than 7 days), bananas, grapefruit, lemons, limes, mandarins, mangoes, melons, oranges, papayas, persimmons, pineapple, plantain, pomegranates, watermelons
Basil (stems in water), cukes+, eggplants+, garlic*, ginger, jicama, onions*, peppers +, potatoes*, pumpkins, sweet potatoes*, tomatoes, winter squashes
* Store in a well-ventilated area in the pantry. Protect potatoes from light to avoid greening.
+ Can be kept in the refrigerator for one to three days, if used soon after removal.
COUNTER TO FRIDGE
These fruits will ripen gradually on the counter, but don’t do well in fridge for long. Refrigerate only when ripe or if cut, and not for more than a day or two.
Avocados, kiwi, nectarines, peaches, pears, plums, plumcots
These foods spoil quickly unless kept cool. But take care not to over-cool your fridge. Icy temperatures hasten fruits’ and veggies’ demise.
Apples, apricots, Asian pears, all berries, cherries, figs, grapes
Artichokes, asparagus, green beans, lima beans, beets, Belgian endive, broccoli, Brussels sprouts, cabbage, carrots, cauliflower, celery, green onions, herbs (except basil), leafy greens, leeks, lettuce, mushrooms, peas, radishes, spinach, sprouts, summer squash, sweet corn
Reproduced from Storing Fresh Fruits and Vegetables for Better Taste by Adel Kader, PhD, Jim Thompson, PhD, and Kathi Sylva, PhD, University of California, Davis, Postharvest Technology Research and Information Center, 2000. Printed with permission of Adel Kader, PhD.