eli5 Why are deeply dented tin cans indicative of botulism?

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I understand that improper food handling piror to the canning process can allow bacteria to thrive once sealed, and that if a food container is punctured then of course any nasties can seep in due to there no longer being a barrier – but why does a deep dent also seem to carry as much risk as the can actually being punctured? Never understood this.

In: Biology

I could be wrong here but I believe it has to do with allowing re-oxygenation to reintroduce disease to a formerly sterile environment.

Once a can is sealed, it’s heated to kill off any dangerous bacteria and do some other stuff. A deep dent can open the can back up to the rest of the environment and allow those pathogens back in.

a deep dent most likely means the can is cracked/has been punctured, hence is no longer a safe seal.

basically any can that looks to be significantly physically damaged shouldn’t be presumed to be safe.

Ah, so short of definitive puncture marks even a deep enough dent could cause sort of microfractures? I guess even if most of the malformed area has just gotten thinner and bordering on fracture – it only takes a miniscule actual break in the barrier for bacteria to enter what was a sterile environment. Seems simple enough but I just couldn’t picture the causality lol – thank you all for your comments helping me think of it in other ways!

Dents can damage the seal of a can, but the usual concern is a can that has swollen, meaning that something inside is generating gas — something alive where it shouldn’t be.

A dent isn’t indicative of botulism. The can bulging is definitely a dangerous sign because it means bacteria are active inside the can. A dented can is only dangerous if it’s been punctured.

Bulging cans are a sign of botulism (insanely rare these days, so the whole question may be moot). If a can is dented, even though otherwise intact, it may conceal the tell-tale bulging.


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