One way to make fruits and vegetables more convenient is to buy them pre-cut and packaged or to cut them up yourself soon after you bring them home. However, cutting, slicing, chopping or peeling fruits and vegetables reduces some of their nutritional value. Learn what you can do to get the most from your produce. The three factors that lead to nutrient loss are heat, oxygen, and light. The interiors of uncut produce are protected from oxygen and light but exposed when cut. The nutrient that suffers the heaviest hit in cut fruits and vegetables is probably vitamin C, although some vitamin A and vitamin E get lost as well. These vitamins are antioxidants, which means they react to oxygen. The peels and coverings naturally protect the antioxidant vitamins inside. Once you break through the protective coverings, the flesh inside is exposed to air and the oxygen reduces the antioxidant vitamins.
Vitamin C is carried by water, which is why it is easier for it to leak out in the fluids released after cutting or in water you may use to rinse the cut produce. Vitamins that are carried in fat, such as vitamin D, do not leach out as easily. Cutting also raises the respiration rate, which results in sugars inside the produce being broken down and carbon dioxide released. This can result in faster spoilage as well as a change in the taste and texture of the produce. Lower temperatures help slow respiration, so pre-cut produce should be kept refrigerated. Most other nutrients, including minerals, B-complex vitamins, and fiber, aren't lost after cutting or peeling the inedible rind from fruits and vegetables. For fruits and vegetables with edible skins or rinds, it's best to eat them intact so you get the nutrients and fiber contained the rind. Potatoes, carrots, and cucumbers, for example, can be simply rinsed thoroughly and used as they are. Time is an important factor in nutrient loss. Look at the dates on the packaging and buy the freshest produce, especially if they are pre-cut. You should only buy pre-cut produce that has been kept refrigerated as low temperatures also reduce nutrient loss.
Ideally, you should eat pre-cut fruit in two to three days and pre-cut vegetables within five to six days. Keep the time limits in mind when stocking up at the market or the warehouse store. They are great for grab-and-go for a snack or making a meal soon, but not the best for long-term storage. And keep in mind that frozen produce is an option as well. Frozen fruits and vegetables often have more vitamins and minerals because they are frozen at peak freshness. They also last longer and are easy to use. The best way to store fruits and vegetables is to leave them unwashed with the skin or rinds intact until the day you plan to eat them. You don't have to wait until the last moment to cut your produce, but be sure you keep them stored in air-tight containers in your refrigerator once you have you cut them.
It's also best if you can leave them in large chunks. Less surface area means less oxygen exposure and more vitamin retention. Use a sharp knife when you cut vegetables or fruit. A sharp knife, as opposed to a dull blade, doesn't bruise the produce as much. As a result, there is less leakage of calcium and potassium and less production of off-odors. Also, be sure you use a clean knife so you aren't introducing bacteria or mold, which will lead to spoilage. Produce starts looking bad even before it begins to lose nutrients significantly. Once your produce has started to shrivel, turn deep brown, or show signs of mold or decay, it's time to compost it rather than eating it. It can be tedious to have to wash and chop whole fresh fruits and vegetables when you're busy with other things. For that reason, pre-cut produce make sense for many people. The small difference in nutrients is completely lost if you don't eat the produce because it wasn't convenient. Having fresh fruits and vegetables all ready to go might make it easier for you to make healthy choices at snack time. So, go ahead and purchase fruits and veggies that have been washed and cut into pieces. Just keep them cold in their containers and remember they won't last all that long.
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What are your concerns? Written by Mary Jane Brown, PhD, RD (UK) — Updated on June 15, 2017 Fresh fruits and vegetables are some of the healthiest foods you can eat. They’re full of vitamins, minerals and antioxidants, all of which can improve health. Eating more fruits and vegetables may even help protect against heart disease (1). Fresh produce may not always be available, and frozen varieties are a convenient alternative. However, their nutritional value may differ. This article compares the nutrient content of fresh and frozen fruits and vegetables. Most of the fruits and vegetables you buy are harvested by hand, with a smaller amount being harvested by machinery. However, what happens after that varies between fresh and frozen produce. Fresh Fruit and VegetablesMost fresh fruits and vegetables are picked before they are ripe. This allows them time to fully ripen during transportation. It also gives them less time to develop a full range of vitamins, minerals and natural antioxidants. In the US, fruits and vegetables may spend anywhere from 3 days to several weeks in transit before arriving at a distribution center. However, the USDA states that some produce, such as apples and pears, can be stored for up to 12 months under controlled conditions before being sold. During transportation, fresh produce is generally stored in a chilled, controlled atmosphere and treated with chemicals to prevent spoiling. Once they reach the supermarket, fruits and vegetables may spend an additional 1–3 days on display. They’re then stored in people’s homes for up to 7 days before being eaten. Bottom Line: Frozen Fruit and VegetablesFruits and vegetables that will be frozen are generally picked at peak ripeness, when they’re the most nutritious. Once harvested, the vegetables are often washed, blanched, cut, frozen and packaged within a few hours. Fruits tend not to undergo blanching, as this can greatly affect their texture. Instead, they can be treated with ascorbic acid (a form of vitamin C) or added sugar to prevent spoiling. Usually, no chemicals are added to produce before freezing. Bottom Line: Generally speaking, freezing helps retain the nutrient content of fruits and vegetables. However, some nutrients begin to break down when frozen produce is stored for more than a year (2). Certain nutrients are also lost during the blanching process. In fact, the greatest loss of nutrients occurs at this time. Blanching takes place prior to freezing, and involves placing the produce in boiling water for a short time — usually a few minutes. This kills any harmful bacteria and prevents the loss of flavor, color and texture. Yet it also results in the loss of water-soluble nutrients, such as B-vitamins and vitamin C. However, this doesn’t apply to frozen fruits, which don’t undergo blanching. The extent of nutrient loss varies, depending on the type of vegetable and length of blanching. Generally, losses range from 10–80%, with averages around 50% (3, 4). One study found that blanching reduced water-soluble antioxidant activity in peas by 30%, and in spinach by 50%. Nonetheless, levels remained constant during storage at −4° F, or −20° C (5). That being said, some research also suggests that frozen produce may retain its antioxidant activity despite the loss of water-soluble vitamins (6, 7). Bottom Line: Shortly after harvesting, fresh fruits and vegetables start to lose moisture, have a greater risk of spoiling and drop in nutrient value. One study found a decline in nutrients after 3 days of refrigeration, when values fell to levels below those of frozen varieties. This is most common in soft fruits (8). The vitamin C in fresh vegetables begins to decline immediately after harvesting and continues to do so during storage (2, 5, 9). For example, green peas have been shown to lose up to 51% of their vitamin C during the first 24–48 hours after harvesting (9). In vegetables stored chilled or at room temperature, antioxidant activity declined (5). However, although vitamin C can be easily lost during storage, antioxidants like carotenoids and phenolics may actually increase. This is possibly due to continued ripening and is seen in some fruits (8, 10). Bottom Line: Results from studies that have compared the nutrient content of frozen and fresh produce vary slightly. This is because some studies use freshly harvested produce, which removes the effects of storage and transport time, while others use produce from supermarkets. Additionally, differences in processing and measuring methods can influence results. However, in general, the evidence suggests that freezing can preserve nutrient value, and that the nutritional content of fresh and frozen produce is similar (2, 7, 11). When studies do report nutrient decreases in some frozen produce, they are generally small (3, 8, 12). Furthermore, levels of vitamin A, carotenoids, vitamin E, minerals and fiber are similar in fresh and frozen produce. They’re generally not affected by blanching (11). Studies comparing supermarket produce with frozen varieties — such as peas, green beans, carrots, spinach and broccoli — found the antioxidant activity and nutrient content to be similar (5, 13). Bottom Line: Frozen produce may contain higher levels of certain nutrients. This is most commonly seen in studies that compare frozen produce with fresh varieties that have been stored at home for a few days. For example, frozen peas or spinach may have more vitamin C than supermarket-bought fresh peas or spinach that have been stored at home for several days (13). For some fruits, freeze drying resulted in higher vitamin C content, when compared to fresh varieties (14). Additionally, one study suggests that the processes undertaken to freeze fresh produce may increase fiber availability by making it more soluble (3). Bottom Line: Freshly picked fruits and vegetables straight from the farm or your own garden are of the highest quality. However, if you are shopping at the supermarket, frozen produce may be equal to, or in some cases, even more nutritious than fresh varieties. At the end of the day, frozen fruit and vegetables are a convenient and cost-effective alternative to fresh options. It’s best to choose a mix of fresh and frozen produce to ensure you get the best range of nutrients. |