How Long Does Food Retain Its Nutritional Value?
Does the week-old zucchini at the back of your fridge have the nutritional value of cardboard? If you are inclined to toss it into the garbage, you might want to reconsider. According to nutrition expert Lora Brown of Brigham Young University, refrigeration vastly improves the shelf life of most fruits and vegetables, and the loss of nutrients usually coincides with visible spoilage. "If you have to take it out of the fridge on a gurney, then throw it away," Brown told Yahoo! Shine. "But if the taste, color, and texture are good, the nutrient content will still be relatively high."
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Unless you are buying all your food straight from the farm, it is impossible to know how it was processed or how long it took to get to the supermarket. "Fresh" produce might be in transit for more than a week and then sit on the store shelf for days. For oils, nuts, and dry goods, it could be months or years before an item reaches your pantry. Ideally, for the best taste and nutrition, we would all be buying locally produced food, but that's not feasible for everyone. There are ways, however, to maximize nutrient retention through proper storage and handling at home.
Fruit and vegetables
Most fresh fruits and vegetables should be kept in the refrigerator in separate compartments. Fruits emit a chemical called ethylene that causes vegetables to spoil more quickly.
Produce that was handled properly can last for two to three weeks. One of the least stable vitamins is vitamin C, which deteriorates rapidly. The acid in citrus fruits helps them retain their vitamin C level so they keep their maximum nutritive value for longer than green vegetables such as broccoli, green beans, or asparagus, which may degrade in 7-10 days. Eric Decker, professor of food science at the University of Massachusetts, points out, "Most people don't eat nearly enough fruits and vegetables. Even if some of the vitamins are lost in storage, they retain their minerals and fiber so they are still good for you to eat."
Though some nutrients are lost in processing, frozen vegetables maintain higher levels of vitamins than their fresh counterparts. "The problem with frozen fruits and vegetables is the texture," says Decker, "if you don't like them, you won't eat them."
Berries
All berries are fragile and very perishable. Their vitamin C content degrades quickly, and they should be eaten within a few days of purchase. Blueberries, if harvested gently and stored in the refrigerator, will last a week.
Greens
Lettuce and spinach are the most perishable greens and should be refrigerated as soon as possible after purchase. They contain vitamin C and also folic acid and vitamin A, other unstable vitamins, so should be eaten within a few days to get the biggest bang for your buck. Visible spoilage happens quickly and coincides with the loss of vitamins. Hardier greens such as kale and cabbage can be stored for two weeks or longer.
Apples and pears
If properly stored in a cool place with ventilation, many varieties of apples and pears can be stored for two to three months and maintain a high nutritive value. Bruising will speed up spoilage.
Potatoes
The best way to store potatoes is in a cool, dark, well-ventilated area away from the stove or other heat-producing appliances. Stored at about 45 degrees, they will be good to eat for up to two to three months. Warmer temperatures cause them to sprout and rot more quickly. Do not expose potatoes to light. This makes them turn green and produce a chemical called solanine that is poisonous in large quantities.
Garlic and onions
Garlic and onions emit gases that can cause spoilage in other vegetables so store them separately. They contain vitamin C and folic acid, which will degrade under poor conditions. The best way to keep onions and garlic fresh is to store them in their skins in a cool, dark, dry, well-ventilated place.
Dry goods
Dried beans, grains, and grain products such as pasta and flour are very stable and should be the backbone of a nourishing pantry. Michelle Lloyd, PhD, of Brigham Young's Food Technology Research Center, says that the key to storing dry goods and maintaining their nutritional value is keeping them away from moisture, air, light, and high temperatures. Stored properly and kept free of bugs, dry goods will last for years.
Oils
Oils go rancid quickly and lose vitamin E when exposed to light and warm temperatures. Decker suggests storing all vegetable oils in the refrigerator. Olive oil gets cloudy and solidifies in the fridge but returns to normal when brought back to room temperature. You can compromise by keeping a small container of olive oil for daily use on the counter and the rest in the refrigerator. "And don't buy monster cans of oil at the big box store," says Decker. It will most likely go rancid and you will have to discard it, losing any savings. Decker warns that new research links consuming rancid oil to heart disease.
Nuts
Like oil, nuts contain unstable vitamin E and also go rancid quickly. If you use nuts for cooking, keep them in the freezer. They will lose some texture but are fine for baking or toasting. For snacking, look for vacuum-packed nuts and consume within a couple of weeks.
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