The coronavirus pandemic has led to significant lifestyle changes for just about all of us, not the least of which involves the way we are eating. People who previously relied on restaurants have been learning to cobble together meals at home, while seasoned cooks have been reinventing favorite recipes using fewer fresh ingredients and more processed foods. It’s no wonder, then, that canned foods joined toilet paper and hand sanitizer as some of the most coveted and stockpiled items in America.
If your can opener is currently in heavy rotation and you’re curious about things like the nutritional value, safety, and history of canned foods, read on. Who knows, you may even be persuaded to keep a stash of canned edibles in your pantry long after the current crisis is all over.
Why, and how, is canning done?
Simply put, canning is designed to keep food safe, nutritious, and palatable long after it would otherwise go bad. It does this through the use of methods that inhibit the growth of harmful microorganisms, deactivate enzymes that cause foods to break down, remove oxygen that contributes to spoilage, and prevent moisture loss. Key to canning is its use of a barrier, in this case an airtight metal can, to keep the food in a controlled environment while being stored. After it’s filled, the can, usually made of recycled steel or aluminum, is given a heat treatment of up to 250°F to eliminate unwanted microorganisms.
How long do canned foods last?
Most canned foods are safe to eat indefinitely as long as the can itself is not heavily rusted, deeply dented, leaking, or swollen (which are warning signs that bacteria or other unwanted organisms might be present). Still, the USDA advises a storage limit of 18 months for acidic canned foods such as tomatoes and other fruit, and two to five years for canned vegetables, beans, meat, and poultry. Consider writing dates on cans to indicate when you purchased them.
“Use by” or “best if used by” dates on canned foods, if present, refer to food quality, not safety. To keep your canned foods at optimal taste, texture, and appearance, store them below 85°F (50°F to 75°F is best, if possible) and away from hot pipes, the stove, and direct sunlight. Making sure the cans don’t get wet is also important because prolonged contact with moisture can cause corrosion, resulting in leaks and spoilage.
Must-Have Cans for Your Pantry
If you have abundant storage space and a robust budget, you may want to indulge in some luxury canned goods (imported marmalade?), but most of us should probably stick with basics that pack the most nutritional bang for the buck. Here are our top picks.
How do canned fruits and vegetables compare nutritionally to fresh and frozen?
Quite well, it turns out. Similar to frozen fruits and vegetables, produce destined for a canning facility is typically processed at peak quality within hours of being harvested, thereby locking in many of its nutrients. In contrast, fresh produce frequently travels over long distances (often under less-than-ideal conditions) before getting to you. During this transit stage—and any storage period thereafter, whether in the supermarket or at home—nutrients are diminished, many of which are preserved in a similar canned item.
A review in the Journal of the Science of Food and Agriculture in 2007 did report that the initial heat treatment of canned foods causes loss of some nutrients, including vitamin C and B vitamins. But the levels subsequently stabilized, meaning that there were no further nutrient losses after canning, owing to the lack of oxygen in the can (compared to fresh produce, which continues to lose nutrients over time).
Moreover, the nutritional profile of certain foods actually benefits from being canned. For instance, canned pumpkin has even more nutrients and carotenoids, ounce for ounce, than fresh because the heat processing eliminates much of the water (making it more concentrated) and releases the carotenoids from the cell wall “matrix” so they are more readily available. The same is true for canned tomatoes and carrots.
Are there any other advantages of canned foods?
A long shelf life may be canned foods’ biggest advantage when you can’t get fresh food, but price, convenience, and year-round availability make them a great choice even in the best of times. Canned food is often less expensive than fresh; prep time is largely dictated by how long it takes you to operate a can opener and, if needed, heat the contents; and snow outside doesn’t mean you can’t have corn or peaches inside.
What should I watch out for when choosing canned foods?
In a word: sodium. Canned foods are typically high in added salt (which is 40 percent sodium, 60 percent chloride). But low-sodium and no-salt-added options are increasingly easy to find. While salt can act as a preservative, it is not required in canned food because the canning process does the preserving. Instead, salt is added to enhance flavor, appearance, consistency, and texture (so you don’t end up with mush). If you can’t find low-sodium or no-salt-added canned beans and vegetables, you can drain the liquid from the cans and rinse the food with water to lower the sodium.
Added sugar is an issue in most canned fruit. For instance, a half-cup serving of Del Monte canned sliced pears in heavy syrup has 14 grams of added sugar, in the form of high fructose corn syrup, sugar, and corn syrup—equivalent to about 3.5 teaspoons of sugar. The “lite” version has less, but still about a teaspoon of added sugar per serving. Look for no-sugar-added canned fruit that’s packed in water instead of syrup.
What about BPA in can linings?
Bisphenol A (BPA) is a chemical used in the linings of food and beverage cans to prevent corrosion and help maintain the safety and quality of the contents inside. But trace amounts—which can migrate out of these linings into the food—have been linked to developmental, reproductive, and behavioral problems in children and cardiovascular disease, type 2 diabetes, obesity, and other disorders in adults. According to the Can Manufacturers Institute, at least 90 percent of the linings in food cans no longer contained BPA as of early 2018; typically, acrylic and polyester formulas are used in place of BPA today. The canned food giant Campbell’s, for instance, has made the switchover in all its canned soups sold in the U.S. and Canada. But you may not easily know what’s in the lining, since canned foods do not reliably state if they are “BPA-free” even if the chemical is not present. Moreover, there is concern that some of the ingredients used in place of BPA, including another bisphenol chemical (bisphenol S), may have properties similar to BPA.
Canning: A Revolutionary Idea—Literally
The popularity of canned foods during crises predates the 2020 coronavirus pandemic and includes the feeding of soldiers during wartime as well as everyday folks during periods of economic depression. Here’s a quick history.
What else should I know about canned food?
- Improperly canned foods and damaged cans provide an ideal environment for bacteria that cause botulism, a deadly food poisoning, to thrive. Though home canning is usually the culprit, any can that is leaking, bulging, or badly dented should be double-bagged in plastic (to avoid leakage of toxins that might be present) and discarded.
- It’s okay to refrigerate unused portions of an opened food can in the original can, but to better preserve quality and flavor (foods, especially acidic ones, can take on a metallic taste from the can), transfer the leftovers to a food storage container with a lid.
- Canned foods do not need preservatives to prevent spoilage—and most, in fact, are preservative-free.
- Top-selling canned foods in the U.S. include chunk light tuna, soup (cream of mushroom, chicken noodle, cream of chicken, tomato), Vienna sausage, sweet corn, spaghetti and meatballs, and green beans.
- It seems just about anything that can be canned has been canned. That includes whole chickens (yup), cheeseburgers, scorpions, roasted crickets, fish mouths, and reindeer, rattlesnake, and crocodile meat.
- Home canning is an old idea that’s still a good idea—if you do it properly. If you have a home garden, you might consider canning surplus tomatoes, peppers, and other produce—or you can turn store-bought fresh vegetables and fruit into canned as a home project. But you must use the right equipment and follow scientifically developed procedures; otherwise the food may not be safe to eat (see botulism risk, above). A reliable resource is the National Center for Home Food Preservation.
Beyond the can
If your ability to shop for fresh food is limited, canned products can be one of your best go-tos for protein-rich foods, as well as for vegetables and fruits, as long as you read the nutrition labels and check the ingredients. But you should also stock up on frozen fruits and vegetables (without sauces or other ingredients that add lots of sodium, fat, or sugar). And don’t forget other shelf-stable foods, including whole grains (such as brown rice, quinoa, and whole-wheat pasta) and packaged milks (dairy or nondairy) and low-sodium broth, as well as nuts, nut butters, and seeds; these do not require refrigeration, though cold temperatures prolong freshness and slow rancidity in high-fat foods like nuts and seeds.
Try This: Chickpea and Farro Stew
This rustic-chic dish involves the same basic cooking technique as pasta e fagioli (pasta and beans), but here the farro lends a delightful chew and subtly nutty flavor.
This article appears in the July 2020 issue of the UC Berkeley Wellness Letter.
Published June 24, 2020