General Question

JackAdams's avatar

Is it "urban legend" or truth, that dented cans on store shelves are "dangerous," and should be avoided?

Asked by JackAdams (6492points) September 7th, 2008

My wonderful mother told me always examine them, to make sure they weren’t dented, because if I ate the contents, I’d get very sick and die.

I always thought that if they were PUNCTURED, that there was a serious health risk, but merely being dented, in and of itself, was nothing about which to be concerned.

So what’s the straight stuff on this?

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28 Answers

jca's avatar

i think it’s a legend, i heard only if the top is bulging is it an issue.

trudacia's avatar

I believe that in rare cases a badly dented can will release a toxin into the food. However, I don’t think it’s deadly.

My main reason for not buying dented cans is that they are a pain to open. The can opener always gets jammed….

Just in case, I would avoid them.

richardhenry's avatar

Dents on the seams of the can – at the top, bottom and along the side seam – may pose a risk as it can make it possible for air to enter, bringing with it some nasty microorganisms (which flourish in the contained, nutritional environment). Smooth dents on the body of the can do not pose a risk.

“If in doubt, throw it out.”

Source: http://www.foodsafetynetwork.ca/en/faq-details.php?a=3&fc=3&id=765

Rusting of the can is another potential thing to watch out for. If it does not wipe away to reveal clean metal, you shouldn’t eat the contents.

JackAdams's avatar

I’ve always wondered why a store would allow a dented can to remain on a shelf, if it was dangerous?

richardhenry's avatar

They probably examine them… you can usually see if the seam has popped open slightly. Or are lazy. I would steer clear of the dented cans anyway.

richardhenry's avatar

Another answer to your question:

“You should NEVER eat from a dented can. I work at a food bank and we throw all cans dented and rusted away. It doesn’t matter if the can does not leak when dented. It relieves pressure in the can and allows bacteria to grow inside the can. It is called botulism, a severe sometimes deadly illness from improper canning or denting.”

From: http://www.answerbag.com/q_view/78105

I’m confused as to how pressure could be relieved without the can being ruptured though. That doesn’t make any sense.

JackAdams's avatar

I agree.

Your first link does not seem to be working for me, respectfully.

richardhenry's avatar

Botulism doesn’t sound fun. “If untreated, these symptoms may progress to cause paralysis of the arms, legs, trunk and respiratory muscles.”

“Foodborne botulism is caused by eating foods that contain the botulism toxin”, which is created by “the bacterium Clostridium botulinum”.

From: http://www.cdc.gov/nczved/dfbmd/disease_listing/botulism_gi.html

Yeah, that first link seems to have died now :S. How very strange.

sndfreQ's avatar

Dented cans are structurally unstable and if they fall off a high shelf, can pose a liability for the store…that’s the only safety issue I’m aware of. That and the obvious issue of contaminants as RH mentions.

JackAdams's avatar

Another question, related to this one: Wouldn’t cooking the foods with very high heat, kill the deadly germs? I mean, isn’t that what boiling does?

richardhenry's avatar

Hmm, I suppose. The problem with canned soup and beans is that you generally don’t boil them, just heat it up to 70 or 80 degrees C. They have, after all, already been cooked. Other food that requires higher cooking temperatures would probably be safer.

Related:
http://en.wikipedia.org/wiki/Thermal_death_time
http://www.cdc.gov/botulism/botulism.htm
http://www.redflagdeals.com/forums/showthread.php?t=137190
http://answers.yahoo.com/question/index?qid=20061111191500AAUasXP

jlm11f's avatar

When I worked in a food store, we were required to get rid of all dented cans. What usually ended up happening is that the employees were able to take those cans home with them for free. This was a campus convenience store, so some college kids thought it was hilarious to tear the outer layer of a bunch of microwave popcorn packet. We had a lot of popcorn parties that month….

My personal opinion is unless it is punctured/open…it is okay to consume.

richardhenry's avatar

The botulinum bacteria dies after exposure to 121 °C for three minutes. My guess is that if a tin of beans contains traces of the bacteria, normal cooking would not eradicate it.

But like PnL said, unless the can is actually ruptured, you’re probably just fine. I wouldn’t go seeking out dented cans in the store, though.

JackAdams's avatar

For those in the USA, the temperature quoted is 249.8° F

JackAdams's avatar

@RH: Usually, the dented cans cost less, than the un-dented ones.

SuperMouse's avatar

Well, all I know is that if it was true, my brothers and sisters and I would be long dead. My father shopped exclusively in in “scratch and dent” section of our grocery store, something about the cans there being marked down.

JackAdams's avatar

@PnL: I tend to think as you do, but wished to learn the opinions of The Collective.

richardhenry's avatar

My guess is that botulism is fairly uncommon. Nobody is going to die from eating from a dented can, particularly because botulism is curable if caught in a reasonable time frame. Other bacteria in canned food is rarer still.

I think we should round this up with some wise words: “forget dented cans, the bulging ones are the dangerous ones.”

Harp's avatar

Two things about botulism:

First, killing the bacteria doesn’t render the food safe. It’s the toxin released by the bacteria that is deadly, not infection by the bacteria. The toxin will remain in the food even after the bacteria are dead.

Second, Botulin bacteria can only reproduce in an anaerobic environment (in the absence of air). Leaky cans won’t be good environments for Botulin precisely because there is air inside. Botulin grows in sealed cans that haven’t been properly sterilized (hence the bulging). Other things will infect leaky cans, but not Botulin.

JackAdams's avatar

Thanks Harp!

richardhenry's avatar

Okay, that’s interesting… There is a lot of emphasis on botulin and punctured cans floating around. But it’s completely the opposite?

richardhenry's avatar

Indeed it is, stupid internet. Thanks Harp.

JackAdams's avatar

No Internet is perfect.

Not even the one on my home planet, QUERTZL.

richardhenry's avatar

Comes close though, I’m sure. If insect aliens can’t do it, nobody can.

JackAdams's avatar

LOL!

Good one!

I like it!

shilolo's avatar

A few more facts to add on to Harp’s excellent answer.
1. The bacteria themselves don’t produce the toxin, but rather, the spores produced in an anaerobic environment (the sealed can) actually make the toxin.
2. Most store bought foods are safe, dent or no dent. Most cases of food botulism occur from home-canning, as individuals can frequently not sterilize their cans, or heat the food to a high enough temperature.
3. Small children (less than 1 year old) are particularly sensitive to food botulism, and outbreaks have been associated with honey (thus the suggestion from pediatricians to avoid giving infants honey).
4. The bulge in the can is a sign of bacterial activity, since even in anaerobic environments, the fermentation process produces carbon dioxide (CO2) gas, which has to go somewhere (thus the bulge).
5. Wound botulism is much more common in the US. I’ve personally treated multiple cases in drug users in San Francisco due to contaminated drugs.

For more info, the CDC has a useful site.

jvgr's avatar

When the use of tin cans began, the whole process was rudimentary at best and primarily and hand made process. This resulted in cans that were much more fragile than those available today. (The crew of the fated Franklin expedition in the 1800’s were victims of lead poisoning from the poorly canned foods that were soldered with excess lead)

I wouldn’t avoid a can with a dent as long as the sealed edge was not affected.

lightningchild's avatar

K i had to do a report on this but I’m just gonna sum up what i found.
Tin cans are actually steel cans with a tin coating on the inside to prevent the steel from rusting. Food inside tin cans almost always contains liquid and is very often slightly acidic (acidic solutions conduct electricity). When a can is dented the tin layer can crack which would allow the acidic liquid to come in contact with both the steel and the tin which creates an electrical current between the tin and the steel. Through the process of the current, some of the steel of the can is oxidised and dissolves in the acidic solution of the food this dissolved oxidised steel is often only in very small amounts. But, if a can is dented enough (ie enough steel oxide is dissolved in the food) it can make you severely ill.

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