How Long Canned Food Really Lasts

A can is cooked food sealed in sterile steel. As long as the seal holds and the metal is sound, the food inside is safe long past the date on the lid. The date was never about safety. What changes over the years is quality, vitamins first, then color, texture and taste, and how fast that happens depends mostly on how warm the room is. I keep a lot of cans, and I get asked about them more than anything else on the shelf, so I put what I know on one page. The pages for each kind of can, from tuna to pumpkin, are linked at the bottom.

Beans against peachesHow long each kind lastsWhat the years doHeat is the enemyThe can itselfReading the stampKeep it or toss itBotulismA shelf that rotates itselfHome-canned jarsThe deeper pages

Canned shelf life comes down to acid. Below a pH of 4.6 the spores of Clostridium botulinum cannot grow, so fruit, tomatoes, pickles and juices only need a hot-water process. Above 4.6 the can has to be cooked under pressure at 240°F or more. Both kinds leave the cannery equally safe. What differs on your shelf is what the food does to the can over the years, and that is why a can of beans outlasts a can of peaches on the same shelf.

Three figures for every kind of can: what the label says, what it really does stored well (a steady 50 to 70°F, dry, dark, off the floor), and how long it keeps in the fridge once it's open. The stored-well figures are the ones my field guide plans around. The label figures are USDA's and the canners' own.

"Stored well" is doing a lot of work in that list. Every orange figure assumes a steady 50 to 70°F, dry air and no sun. Move the shelf to a garage that hits 95°F in July and you are back to the label figures or worse. The heat section has the arithmetic.

The date on the can is the canner's guess at when quality starts to slide. Safety is a different matter. A sound seal on a sound can is sterile, and sterile does not expire. Quality slides in a known order.

1. Vitamins, and most of that loss is at the canneryThe UC Davis review of canned, frozen and fresh produce (Rickman, Barrett and Bruhn, 2007) found that canning itself costs vegetables an average of 60 percent of their vitamin C and up to two thirds of their thiamin. On the shelf the loss is slower: generally under 15 percent more over 18 months, and green beans lost none at all in two of three studies. Extension figures put the ongoing loss of the fragile vitamins at 5 to 20 percent a year depending on the room.
2. Protein, minerals, fiber and fat holdNiacin retention runs above 93 percent, riboflavin 68 to 95. Minerals do not care about time; the only change is a little iron and tin picked up from the can. Fiber stays. Vitamin E is often higher in canned than fresh. Canned tomatoes carry more lycopene than fresh ones, because heat frees it.
3. Then color, then texture, then tasteFruit darkens, vegetables soften, meat fibers loosen, sauces separate. None of it is spoilage. A can of ten-year-old green beans is soft, dull and perfectly safe; it belongs in soup, not on a plate.
4. Safety, last, and only if the can failsNothing on a shelf of sound commercial cans can grow. The dangers are physical: a seam cracked by a deep dent, a pinhole from rust, a seal split by freezing. Keep the cans dry, cool and off the concrete and the organism never gets in.

Heat speeds up everything that happens inside a can. The rule of thumb USDA and Utah State use is that every 18°F (10°C) of warmth cuts quality shelf life roughly in half. The Codex canning code says the same about the can: tin dissolves off the wall about twice as fast for every 10°C. The FSIS table for military rations is the clearest picture anyone has published: 7 years at 60°F, 4.5 at 70°F, 2.5 at 90°F, 1.5 at 100°F, one month at 120°F.

Most cans now have a printed best-by date. The rest have a packing code, which USDA says is for the canner's own rotation and recalls, not for you. Four kinds of stamp cover nearly every can on the shelf.

Look at the can before you open it, listen as you open it, smell it before you eat. Five seconds a can, and the call is almost always obvious.

The thing you are guarding against is botulism, and botulism has no taste, no smell and no cure outside a hospital, which is why anything on the toss list goes unopened.

Commercial canning is built around killing one organism. Clostridium botulinum spores survive boiling, so low-acid food is cooked in the sealed can at 240°F or hotter under pressure, which no home kitchen reaches without a pressure canner. FSIS calls botulism from a commercial can extremely rare. The CDC's outbreak records tell the other story about jars: in the lower 48 states, 91 percent of botulism outbreaks came from food that was not commercially produced, most often home-canned vegetables.

The canned pantry that works is the one you cook from every week. The field guide's numbers for one person for one month come to about 45 cans. A family of four for three months is that times twelve, four cases of each, which fits on two shelves of a closet.

1. Store what you eatTwelve cans of each of the ten things you actually cook with is a deeper store than a hundred cans of one thing nobody likes. Chili, tuna, beans, tomatoes, corn, green beans, peaches, soup: the cans you open every week are the cans that rotate themselves.
2. Date every lid the day it comes homeMonth and year in marker. New cases go behind the old ones; shop from the front.
3. Two shelves, two clocksFruit, tomatoes and juice at eye level where you see them and use them inside two years. Meat, fish, beans and vegetables below, where the room is cooler and they can sit for five.
4. Count by category, not by canA running tally on the pantry door: meat 24, beans 18, vegetables 30. Replace what you used on the next grocery run. That one habit does most of the work, and it costs nothing.
5. Pull and cook once a quarterAnything past its stored-well figure for its kind comes to the kitchen counter and gets cooked this week. Cases on a board or a pallet, never on concrete, which sweats and rusts the bottoms.
6. Two openers and a way to heatA shelf of cans is stuck without an opener, and a plain steel one lasts forever. Everything on the shelf is cooked and can be eaten cold, but a camp stove and a pot turn a can of beans, a can of tomatoes and a can of meat into a pot of chili with no water and ten minutes of heat.

The food shopping list has the per-person amounts for the whole shelf, canned and dry.

A home-canned jar runs on the same two clocks, with less margin. The USDA Complete Guide says to use home-canned food within a year for best quality and to store it at 50 to 70°F, out of light, never above 95°F. The National Center for Home Food Preservation adds that until the vacuum seal is broken, nothing can get in, so a jar with a sound seal is not unsafe at year two; it is just not at its best.

Every canned page on the site.

Sources: USDA FSIS, Shelf-Stable Food Safety; the USDA Complete Guide to Home Canning; CDC, Botulism and home-canned foods, and Sobel et al., Emerging Infectious Diseases 2004; Rickman, Barrett and Bruhn, Journal of the Science of Food and Agriculture 2007; Codex Code of Practice CAC/RCP 60-2005 on tin in canned foods; Utah State University Extension on storage temperature; the FDA on BPA in food contact; Can Manufacturers Institute; Del Monte, Goya, Hormel, Carnation, Red Feather and Mountain House published shelf life statements; the Bertrand analysis as reported by the National Food Processors Association and FDA Consumer. Stored-well figures are the Survival Foods field guide's.