How does canned food go bad?

canned food relatively safe bacterial action, there can exceptions if fx production temperatures not correct -- causes "bulging" cans.

canned food not safe chemical reactions. metals used in can may react food , contaminate it. if can sealed solder containing lead, lead diffuse food, , not healthy. cans older 20 years made metals , should not trusted. modern cans made inner polymer lining avoid such contamination, then, production errors can give rips or holes in lining metal , food can @ each other.

finally, cans can corrode outside until holes appear (through bacteria , whatever else can contaminate food).

heat , moisture accelerate corrosion , chemical reactions, storage in cool dry place improves can's chances of remaining , edible.

of course, can lucky , have can still edible after hundreds of years, can unlucky , can has gone bad after few years. maybe before expiration date.

bottom line, contrary popular belief, not true canned food "never goes bad". @ least not without lot of caveats such perfect production, cool dry storage, non acidic food, etc.

i heard have shelf life of long don't remember how long how go bad?

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