Canning books and websites generally say that canned foods should be consumed within a year. But it's important to remember this is a "best by" date, not an expiration date. That is to say, after a year's time, the food will very gradually begin to lose nutrients and flavor, but it's still quite safe to eat. In fact, I've eaten home canned food that was more than a decade old and it didn't taste any different than food canned the day before I ate it. (A fun bit of trivia: The oldest known canned food that was opened and eaten was a 118 year old can of veal. No one died or go sick. Here's another fun story about very old canned food that was still safe to eat.)
Tips for Making Home Canned Food Last a Long Time
Of course, your canning methods make a huge difference in how safe your home canned food is, and how long it lasts on the shelf. Older methods (for example, putting hot jam into a jar, putting the lid on, then flipping it upside down in order to get the jar to seal) often lead to food that not only isn't as safe to eat, but also doesn't last nearly as long on the shelf. There are plenty of people who will deny this. ("But Grandma always did it this way...") Yet over and over again these same people complain they find spoiled jelly in their cupboard or that they have a "stomach bug" after eating their home canned food. (For the most up-to-date and safe canning methods, visit the National Center for Home Food Preservation website.)
How you store your home canned food also goes a long way toward making it last virtually forever. Keep jars in a relatively cool, dark location. Storing jars where they get hot (for example, near a furnace or in the attic), where they will be exposed to sunlight, or where they will get damp (like a basement), all contribute to a shorter shelf life.
Looking for Signs of Spoilage in Canned Food
Whether your canned food is decades old or just a day old, always inspect jars for signs of spoilage:
* Inspect the lid before opening. If it's bulging up at all, the food has spoiled and should be carefully disposed of. (Canning jar lids should always be concave, if properly sealed.) Another sign that the food has gone bad is if food is leaking from the lid.
* Pay attention as you open the lid. If it comes off with no effort, don't eat the food, because it did not have a strong seal and could be spoiled. Likewise, if the food explodes out of the jar when you open it, it's gone bad.
* Toss out any food that is bubbly, scummy or moldy, or has an unnatural or bad smell.
If canned food displays these signs of spoilage, do not taste the food! Throw it out. Because deadly botulism could be present, experts recommend putting the unopened jar in a plastic bag, sealing it off, and disposing of it in the garbage. If the jar is leaking, do the same, but be sure to clean any surfaces that have touched the jar (like a shelf or countertop) by wearing rubber gloves (botulism can get into your body through the skin) and sanitizing the area with 1 part unscented chlorine bleach to 5 parts water. Let the mixture stand on the surface for 30 minutes before rinsing. Dispose of the gloves and towels or sponge you used by putting them in a plastic bag, taping it closed, and putting it in the trash. Apply the bleach mixture again, let sit 30 minutes, and rinse. Again dispose of all cleaning materials, like gloves.