No Preservations?

How do frozen and canned produce compare to fresh in terms of nutrition?

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By now most people know the important part fruits and vegetables play in a healthful diet.

Study after study backs up that fact.

But the commitment to eat more fruits and vegetables isn’t the only decision that needs to be made. Go into the grocery store in search of some apples, bananas, cucumbers or cauliflower, and you’ll have to make another choice: fresh, frozen or canned?

It’s common to hear people sing the praises of fresh produce – but “fresh” doesn’t mean “perfect.” The key to getting the most out of fresh fruit or vegetables is minimizing the time it spends in the transition from plant to stomach. As nutrient-rich as most produce is, those nutrients start to leach out as soon as the item is harvested.

Something you picked out of your own garden and put straight into a salad is going to retain most of its original nutrients. Something you grabbed at a farmers’ market is probably only a day or two old, and is also going to be fairly nutrient-rich.

But with an item that’s been sitting on a grocery store shelf for a while, nutritional value is going to be lower. And that’s only compounded if it took the item some time to get to the store – say, if it had to be shipped from another part of the country. Not only will the item lose some nutrients over time, it may also be exposed to extreme temperatures, which will only worsen its condition.

For that reason, if an item is canned or frozen at the peak of ripeness, it may retain more nutrients than a not-so-fresh piece of “fresh” produce.

A study by the University of California Department of Food Science and Technology, published in 2007 in the Journal of the Science of Food and Agriculture, compared the three states in response to an ongoing push for more fresh produce in diets. The effects of preservation on carotenoids, vitamin E, minerals and fiber were all examined, and the study concluded that the nutrient levels of frozen and canned items were comparable to those of fresh items.

“Although fresh-picked produce stored for a short time under optimal conditions and consumed raw will most likely provide maximal nutrition, the availability of such produce is limited by region and seasonality,” the study concludes. “Furthermore, in some cases, processed products have been associated with greater extractability and bioavailability of lipid-soluble nutrients such as beta-carotene and lycopene.”

It’s important to keep in mind the means of preservation the item undergoes. With vegetables, salt may be added as a preservative, especially when the vegetable is canned, so it’s worth reading the nutritional information and finding out just how much was used. Canned vegetables with little or no sodium often tout that fact on special labels.

Canned vegetables preserved with salt can be drained and rinsed off before eating to reduce some of the sodium content. A study by the Beltsville Human Nutrition Research Center in Maryland shows that draining and rinsing can cut salt by 9 to 23 percent. That method also washes away water-soluble nutrients, though; in the study, vitamin C levels, for instance, dropped by 5 to 28 percent after draining and rinsing.

For fruits, especially canned fruits, it’s syrup you should watch out for; an item canned in water or its own juices is lower in calories and carbohydrates, according to information from the American Diabetes Association. Avoiding sugar also means avoiding frozen fruits that have been artificially sweetened. And when eating fruit canned in its own juices, don’t ignore the juices; they retain nutrients, too.

The University of California study acknowledges that “concerns regarding added ingredients in frozen and canned fruits and vegetables are warranted,” though its research on the topic was limited to the effects of added sodium.

In addition, even if an item is preserved when it’s at its best, steps taken during the preservation process can damage nutritive value. Heat is the biggest offender. The heat of canning costs nutrients, and if an item is blanched prior to being frozen – a common method for retaining color and texture – that costs nutrients as well.

“The vitamin content of most foods was most dramatically decreased by canning, while smaller effects were observed upon blanching and freezing,” reads the abstract of a 2000 food processing study by the Department of Biochemistry & Molecular Biology at Wright State University.

A 2007 study undertaken at Oregon State University examined the effects of acids, oxygen, light and heat on key nutrients – vitamin A, vitamin C, folacin and mineral salts – in fruits and vegetables. The study shows that, while mineral salts are not significantly affected by any of the factors, light has an effect on all three of the others and acid affects vitamin A and folacin and oxygen affects vitamins A and C.

“Nutrient loss occurs during all types of preservation,” according to the Oregon State study. “Blanching vegetables (to destroy enzymes) before freezing and drying reduces the amount of heat-sensitive and water-soluble vitamins to some degree. The heat of canning leads to nutrient loss.”

Heating an item before serving also reduces nutritive content, so it’s generally recommended that fruits and vegetables spend as little time being cooked as possible.

The nutritional value of preservation can also vary from foodstuff to foodstuff.

Take tomatoes, for instance. Tomatoes are known to be rich in lycopene, a powerful antioxidant, and research has shown that lycopene is effective at fighting free radicals and may be able to help prevent prostate cancer, per a 2002 study at the Harvard School of Public Health, and stroke, per a 2012 study in the journal Neurology.

When canned, tomatoes are preserved with heat, which releases lycopene, and that means canned tomatoes may be ideal. Val Jorgensen, owner of New Albany-based Jorgensen Farms, certainly prefers them.

“For everything else, my understanding is that the nutritional value decreases with heating,” Jorgensen says.

Jorgensen is familiar with all three common states of produce. In addition to the fresh produce she sells at farmers’ markets, ships to restaurants and keeps for her family’s own use, the farm also freezes and cans items, though its canned products are not available commercially. She generally prefers frozen to canned.

For all frozen and canned items, Jorgensen makes sure the items are preserved the very day they are harvested. Outside of the lemon juice that goes into her pesto, she uses no preservatives.

“I’m sort of a purist,” Jorgensen says. “I want real food, and preservatives don’t fall into the category of real food.”

Garth Bishop is a contributing editor. Feedback welcome at gbishop@cityscenemediagroup.com.

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