Keeping the Harvest Fresh

comments (2) July 7th, 2009

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The humidity factor

Vegetables, just like all living creatures on earth, are made mostly of water. We know this from watching parched spinach wilt under the sun on a dry June afternoon. You should harvest vegetables early in the day, after the glistening morning dew drops have disappeared, but before the sun reaches its highest, hottest point. If you harvest that spinach limp, it never will recover.

Vegetables lose their turgidity, or state of being swollen with water, and wilt in the kitchen just as they do in that dry June garden. From the moment vegetables are harvested, they are cut off from their water source-their roots and the soil-and they lose water until they die. The evaporation of water vapor from the vegetable, a process called transpiration, is simple: water wants to move from an area of greater concentration to an area of lesser concentration. Since water is more concentrated in a vegetable than in the air, vegetables lose water. Transpiration also depends on the temperature and the amount of air movement. Normally, when a vegetable's water evaporates, a moist water vapor barrier forms around it, making less water want to evaporate. When there's a lot of air movement, the vapor bar rier can't form, and water escapes from the vegetable like a barefoot gardener from a nettle patch.

You can control transpirational water loss by keeping an eye on the humidity, temperature, and amount of air movement. Wilted and shriveled beets left in a dry fridge are a sorry sight. To keep them from withering away, increase humidity and reduce the temperature. Put harvested beets in a plastic bag or container. This raises the humidity, reduces air movement, and artificially strengthens the vegetables' vapor barrier. Your refrigerator's crisping drawer, basically a plastic box inside the fridge, attempts to decrease transpiration, but often fails because it is not well sealed. Place the contained beets in the fridge, and enjoy beautiful beets for months. To further increase your refrigerator's humidity, you can spritz the inside with a misting bottle.

This storage method also works well for broccoli, carrots, kale, parsnips, turnips, radishes, and most other refrigerator-tolerant vegetables. But be sure to remove any non-edible vegetable parts like carrot tops. These extra leaves just extend the evaporative surface, making vegetables wilt more.

Leafy greens like lettuces are particularly vulnerable to moisture loss and wilting. Wrap them loosely with damp paper toweling and store them in a plastic bag to maintain humidity.

While most vegetables enjoy a relative humidity between 85% and 90%, others are ruined by moisture. High humidity forces onions and garlic to sprout, and makes winter squash and pumpkins rot. These crops like it somewhat drier; the normal humidity in a typical house is fine. Onions, garlic, shallots, winter squash, and pumpkins should be kept in a dark, cool room or cupboard.

Disease is always lurking

Be wary of standing water for it is the perfect travel guide and locksmith for disease. Droplets carry bacteria and fungal spores from place to place and help them plant their feet, so to speak, in pores and wounds in a vegetable's skin. One droplet of water on a zucchini can lead to bacterial and fungal pits, oozes, and mush. So if you wash soil from your veggies before storage, make sure to dry them thoroughly. In general, it's better not to wash vegetables before storage.

Instead, gently brush off soil after harvest and wash them as you eat them. Wounding also equals disaster in vegetable care. Any injury is dangerous, be it a slight bruise from dropping a pepper or a surface scratch from a jagged edge in your harvesting basket. Wounded spots turn brown and welcome fungal infection, causing the injured vegetable to lose water faster than normal. Wounded tissues also generate ethylene gas, which may cause some vegetables to ripen and perish too soon. All in all, it's best to eat damaged vegetables quickly. And be careful not to keep them with perfect vegetables; if you discover any damaged ones after they've been stored, remove them.

Ethylene gas hastens ripening

According to legend, long ago in eastern countries, fruits were taken into incense-filled temples to hasten ripening. We now know that the burning incense created ethylene gas, which ripened the fruits quickly and evenly. We have all heard about putting unripe tomatoes in a paper bag on a kitchen counter to quickly turn them as red as a parade of fire engines. This works because the bag traps the ethylene gas created naturally by the tomatoes. To ripen a tomato really fast, you can add to the paper bag an apple, banana, or cantaloupe, all of which give off lots of ethylene.

My grandmother used to pick all her green tomatoes at dusk the evening of the first predicted frost. She brought them into her basement, carefully piled into plastic grocery bags, and laid them out on a big wooden table. She left each one cradled with a cushion of free-moving air to prevent ethylene buildup. She noticed that the tomatoes lost more water this way, but these fruits ripened slowly, one by one, for months. The immature tomatoes never ripened, and some of them rotted, but since she could see and remove the bad ones, the rest stayed in good shape, providing her with a steady supply.

If you plan on storing vegetables for a while, ethylene may become an enemy instead of a friend. Since ethylene build-up hastens the ripening of fruit-type vegetables, it also makes them quick to perish. Celery, cabbage, carrots, potatoes, onions, and leafy greens can be harmed by ethylene, too. If you plan to keep apples or cantaloupe in the fridge, seal them loosely in a separate bag or drawer to prevent harming your other produce. Keep a close eye on them, though, because sealed up, these fruits will ripen and expire more quickly.

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posted in: Preserving (Canning, Drying, Freezing)

Comments (2)

CameronRobertson writes: It's such a sense of achievement when your garden yields something that's worthy of being kept in storage in the kitchen pantry isn't it!
Posted: 11:14 pm on March 1st
bradxray writes: I was having the same problem with most of my veggies wilting. I saw this guys video and tried it. It works great! He just treats them like roses. He cuts the stem and then puts the stalk in water for a few hours. Even if they are alreay wilted, they will perk right up.

Posted: 4:11 pm on October 6th
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