Why, hello! We’re so glad to see you made it past the velociraptornadoes, sinkhole maze, and fire ants made of literal fire to join us here in our Survival Week bunker. Please help yourself to a single (one, please!) rationed water bottle as we discuss our now increasingly urgent question: Does tinned food go bad?
Why not just check the expiration date?
Okay, sure, one way to try and answer this question would be to just grab the nearest canned good and flip it over. Chances are you’re going to find a date somewhere on that can, and chances are that date will be somewhere inside of the next five years. But that date, though it may look like an expiration date, is not.
What you’re actually looking at is simply a recommendation, based more on questions of taste and appearance than on any attempt to determine when the food inside may actually spoil. With the exception of baby formula, the presence of that best-by date on canned foods is totally optional—although the government does issue suggestions for how long of a shelf-life manufacturers may want to recommend, depending on what’s inside each can. The longest recommended shelf lives tend to be for foods with a basic PH level (canned meats or soup, for instance), while anything a little more acidic (like tomatoes, pineapple, fruit cocktail, and pickles) is going to get a much shorter timeframe of under 18 months.
So when does it expire then?
While the look, taste, and texture of the food may get a little off beyond the recommended dates (spending years floating in liquid does not always do beautiful things to the color, shape, and consistency of fruits and vegetables), the food is unlikely to actually spoil within that timeframe or anything even close to it. In fact, there are plenty of stories of canned goods making it several decades past those dates with little bad effects. One analysis of a ’30s-era can of corn, retrieved from a 40-year-old shipwreck, even showed that its nutrient levels were pretty close to the levels of initial processing.
That doesn’t, however, mean that canned goods can’t ever expire. It just means that the can itself might actually go bad long before the food inside of it does.
While the contents of the cans vary wildly, the cans themselves are pretty uniformly constructed. They are mostly made of sheet steel that has been welded shut along a seam. Along with this outer package, there’s also often an additional inner-layer designed to keep the metal of the can from coming into direct contact with the food (a design element included primarily to keep that slightly tin-ish flavor out of your tomatoes, pineapples, and green beans).
Altogether, it’s quite a sturdy little container—and one that can stand up to a fair amount of wear, tear, and, yes, time. But it’s also one that is capable of eventually rusting out or even breaking either partially or in full if it gets banged around enough. The USDA offers the helpful advice of avoiding eating anything out of “bulging, rusted, leaking, or deeply dented cans,” which seems like a pretty solid culinary suggestion all around, but becomes even more so when you consider why they suggest it.
Sealed inside its little tin chamber, the food is mostly kept safe, but when that barrier is even slightly breached—whether through a slight corrosion, a broken seal, or a tiny break in the metal—all kinds of bacteria can make their way in, most worryingly, botulism.
If the can appears normal and intact, though, the Food Safety and Inspection Service says that you can expect the food inside to stay, if not exactly good, then at least edible for an indefinite amount of time, advising that “as long as the can is in good shape, the contents should be safe to eat.”
Okay, so how do you keep the cans in good shape?
You can keep your canned goods tasting good longer by taking care of them. Don’t freeze them (or leave them outside in freezing or near freezing temperatures). Likewise, be careful of letting them get too hot. You want to store them at a comfortable room temperature, and you want to make sure you don’t leave them someplace where they can get wet.
If your cans fall or roll, give them a once over to check for any large dents or small breaks. Whether they’ve fallen or not, though, take a good look before you crack them open. Check for any leaking, rust, swelling, or anything odd-looking about the can, and if you do see something, don’t risk it.