All are sterilised by heating during manufacture. The sealed can or other package prevents contamination during storage and transport. Spoilage by microbes therefore does not occur with correctly processed canned products. Slow chemical changes do proceed in canned food, however, so the food will have a long but not an indefinite storage life. The storage life depends on several factors, but especially on the nature of the food and the conditions of storage.
Canned foods have a storage life of up to four years.
As a general rule, the lower the storage temperature, the longer the storage life will be. Buying Canned Foods You should read the label on the package carefully either at the time of purchase or before storage. A small number of canned products, e.g. some fish products, are not fully sterilised and must be kept refrigerated at all times. This requirement will be stated on the label and such products should only be bought if they are displayed in a chill cabinet in the retail store. You should not buy or open canned foods if the package shows signs of swelling or leakage or, in the case of metal cans, there is more than a small amount of external rusting.