Lifespan of Canned Food

The standard published rule of thumb is that home-canned goods are fine for a year.  I've noted elsewhere that some of the things I have canned have been good for far longer.  However, I haven't yet had anything age more than about four years before using.

Home-canned foods aren't good for extreme long-term storage, as this picture shows.  This looked like fruit, probably peaches but there's no way to tell.  There's also no telling how long ago it had been canned (the Atlas mason jar was, as far as my quick online search can determine, probably made before 1964--of course, jars can be used repeatedly over a long period of time).

I found this collection in the basement of a house I was looking at a few years ago.

If you look closely, you can see some mold at the top of some of the jars.  I would've tossed these, and I'm sure whoever bought the house did...though it might have been interesting to do a nutritional analysis on non-moldy ones.

In the house I eventually bought, there were some 1994-vintage dilly beans.  They looked about the same and I tossed them intact into the dumpster.  The jars weren't anything different from what could be bought today--Kerr or Bell--as far as I could tell.

So when you can it yourself, it might not last all that long.  However, in most cases you'll be canning things you use, and even if you can more than a year's supply at once, if you diligently rotate you'll never be opening jars more than a few years old.

What about commercially canned products? There are websites suggesting that the storage life of undamaged and un-bulged cans can be essentially indefinite.  One even mentions a study from the Journal of Food Science in 1983 that examined several cans of food up to about 100 years old (though the authors apparently didn't go as far as tasting the century-old oysters or even the 40-year-old corn).  From personal experience I have seen a couple of things:  I decided to open a can of corn that was about 10 years past its use-by date one time to see how it would be; it wasn't as good as new but wasn't bad.  And I have also seen cans go bad; I have had a couple of bulged cans myself over the years and my mother occasionally had a can of beans or another vegetable rupture and spew.  Can perforation or failure to seal is another possibility.  One time a long-forgotten can of some pasta dish dessicated over some time period, becoming like a freeze-dried meal...except it wasn't.  I didn't open the can but tossed the whole thing.  Acidic foods are allegedly more likely to damage the structural integrity of the can.

Canning is only one of the ways to extend the life of food.  Dry-canning is another (putting already low- or no-moisture foods in an oxygen-free environment), as is dehydrating (with or without subsequent dry canning).  But canning (in the conventional 'wet' sense) has a role, too, even if it doesn't last forever.