Aluminum cans not only protect food from contaminants but also from exposure to light that causes premature spoilage. Unless a can is dented, bulging or its seal has been broken, the food it contains is generally safe to eat for several years past the "sell-by date" imprinted on the bottom.
It's a Date
Food manufacturers are required to inform grocery distributors as to how long they should keep canned products on their shelves; this date generally indicates how long the contents will remain at peak freshness. If you store canned goods properly, they should remain safe to eat during the two-to-five-year expiration date stamped on the can. High-acid foods, such as canned tomatoes or tomato-based products, should be stored no longer than 18 months, as the acid they contain may penetrate the metal.
External influences, such as dampness, extreme heat, the threat of freezing and temperature fluctuations, greatly affect the quality of most foods, including canned goods. Store canned foods in a dark, dry cool place that stays a consistent temperature of about 50 to 70 degrees Fahrenheit. When handling canned goods, be careful not to bruise, puncture or dent the cans. If that happens, use those foods up right away or discard them; their quality will deteriorate very quickly, and they may not be safe to eat after a very short time in storage.
Powers of Observations
Inspect your stored canned goods often and use the first-in-first-out method of rotation, which means using the foods in the order in which they were stored. If you live in an area that experiences lots of humid weather, look for any rust that develops on the lids, as it can eventually eat holes through the metal. A hissing sound is normal when you open a can, but if the sound is loud and liquid spurts out, the food is most likely spoiled.
Recommended Daily Requirements
The mineral content of foods is not affected during storage, but the content of vitamins A and C drops quickly during processing. The Utah State University Cooperative Extension states that this level slows, however, to 5 to 20 per cent during each subsequent year. While additional cooking may reduce the nutritional properties of canned foods, it's a good idea to bring them to a boil, particularly if you've had them a while. Discard any foods that exhibit any signs of spoilage or that smell "off" or bad.