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Last updated on April 23, 2014 at 12:30 EDT

Knowing When To Toss Canned Foods Can Be Confusing

March 12, 2008

It’s spring cleaning time. What about that can of beans or box of pancake mix sitting in your cupboard? Are these still edible?

And what about the food storage in the basement? Should you be eating food that’s older than your kids? Or even older than you?

Dates on the packages offer some clues, but these can be confusing because the United States doesn’t have a uniform system of food dating. Product dating isn’t federally required, except for infant formula and some baby food, according to a U.S. Department of Agriculture fact sheet. Also, stores aren’t legally required to remove food once a “sell by” date has passed.

If there’s a shelf-life date on a package, trust it. However, keep in mind that there’s a great variation with type of food, the temperature where it was stored, the original quality of the food, the amount of oxygen present and other factors, said Oscar Pike, the department chairman of nutrition, dietetics and food science at Brigham Young University, who has studied the shelf life of food.

“People would like it to be more consistent, but it just isn’t,” he said.

Here are the dates you are likely to find on your package and what they mean, according to the USDA:

– “Sell by” tells the store how long to display the product for sale. For best quality, people should buy the product before this date expires, but it doesn’t necessarily mean the product is bad once it reaches that date.

– “Best if used by (or before)” is recommended by the manufacturer for best flavor or quality. This is not a safety date, according to the USDA. If the date says March 11, 2008, and today is March 12, that doesn’t automatically mean you have to toss it. The products, in general, are still safe to eat, but some consumers may detect changes in product flavor, color, taste or texture.

– “Use by” is the last date recommended to use the product, such as “Do not use after March 12, 2008.” The date has been determined by the manufacturer.

– “Closed” or coded dates are packing numbers or dates, so that manufacturers know when and where the product was produced. This is helpful in the event of a recall. The product may be stamped with a date preceded by the letters “MFG.” This tells you the date it was packed. You may have bought the product a month ago, but this date could tell you that it has been sitting in a warehouse or on a store shelf for several months.

The manufacturers’ dates on packages and canned goods are conservative and based more on quality than safety, said Dr. Frost Steele, a BYU food science professor. “The quality deteriorates much sooner than safety will.”

However, you should toss out any cans or jars that are bulging, heavily dented, cracked, with broken seals, loose lids or “any compromise with the packaging,” Steele said.

While extremely rare, a botulism toxin is the worst danger in canned goods, and even tasting a tiny amount can be deadly, according to a USDA food-safety bulletin. In addition to the above warning signs, never use food with a foul odor or that spurts liquid when the can or jar is opened.

The bulletin also states that can linings might discolor or corrode when metal reacts with high-acid foods, such as tomatoes or pineapple. But as long as the can is in good shape, the contents should be safe to eat, although the taste, texture and nutritional value of the food can diminish over time.

There are discount stores that sell items past their “sell by” dates, and several Web sites, including one called the Freegan Kitchen (www.freegankitchen.com), are dedicated to the practice of foraging through grocery store Dumpsters for food that has been discarded, often because of an expiration date.

The Freegan Kitchen authors write that they have never become sick from anything they’ve eaten from the Dumpster.

But most of us tend to live more cautiously. If you choose to buy (or forage) items that are already past their sell-by date, it’s best to use them quickly.

Some low-moisture foods, such as dried apples, beans and rice, can be safe, edible and nutritious up to 30 years after being packaged, if properly stored, according to Pike. He recently conducted research to find out how long foods in long-term storage fared, asking for donations of food that had been stored for a number of years in large, restaurant-size cans.

“A lot of people were happy to get rid of their old food storage, so we received sufficient samples that we could look at the quality,” Pike said.

They tested the food for nutritional value and prepared samples for 50 taste-testers, in a cross-section of ages, to rate. They used a nine-point hedonic scale, with one being “dislike extremely” and going up to nine for “like extremely.”

“Our acceptable cut-off point was “dislike slightly, because this was food that people would be willing to eat in an emergency but that was still well-accepted in sensory perception,” Pike said.

In some cases, there were changes in flavor, appearance, texture or smell that some of the tasters disliked slightly. “But the wheat kernels hardly declined after 30 years. They made a great loaf of bread,” Pike said.

And the 30-year-old apple slices were so well-liked that people continued to nibble on them.

Wheat and white rice were deemed acceptable at 30-plus years. Pinto beans, apple slices, macaroni, rolled oats and potato flakes all were acceptable at 30 years, and powdered milk at 20 years.

Pike points out that these findings apply to the large, food- storage size cans, stored with oxygen-absorption packets, and stored at room temperature or below. Heat, light and air will cause the food products to deteriorate more quickly.

“It doesn’t apply to foods packaged or stored in other ways,” Pike said. They sampled dried milk stored in cardboard packages for 20 years, “and it was terrible, in both nutrition and taste,” Pike said.

He noted that in determining a “best if used by” date, manufacturers don’t go down to a “slightly dislike” level of acceptability. “They don’t want any decline in the quality, because they want to please their customers. They won’t stand behind the food after that date.”

All foods lose nutritional value, but nutrients are lost at a quicker rate than others. Vitamin C, in wet form, deteriorates rapidly. But in a dry pill form, it kept mostly intact after 20 years. Minerals and calories remain the same.

He suggests people rotate their food on a first-in, first-out basis. But if the “best if used by” date says March 13, that doesn’t necessarily mean you should pitch it on March 14.

“The rate of decline is not such that there’s something magic about it,” he said.

People who hate to waste food often think of donating it. But if it’s too old for you, it’s too old for the Utah Food Bank.

“Our rule of thumb is, if you wouldn’t eat it, we’d rather it not be donated,” said Jessie Pugh, a Utah Food Bank spokesman. “If it’s past the expiration (or ‘use by’) date, we can’t use it. If it’s a ‘best if used by’ date, we will accept it within a three-year window and look at the condition of the can.”

Volunteers examine the condition of all donated items, for bulging cans or lids, dents and so on.

The Food Bank will accept food packaged at a cannery where the ingredients are listed. But it won’t accept home-processed and self- packaged food.

“We tell people that by discarding food that doesn’t meet our criteria, you are protecting those who are at risk in the community,” she said.