Can I drink this without dying?
June 20, 2011 3:58 PM   Subscribe

What's the matter with these soda cans? I have two cans of diet pop that are bulging on the bottom (pics inside). Is this botulism or does it pose any danger?

About a week ago I bought a 12 pack of Diet Sierra Mist from my local grocery. I just opened it today, grabbed a can and noticed something odd; the bottom of the can is bulging out in a squarish shape [pic]. I checked the rest of the case, and found one other can that is also bulging on the bottom, this time in a triangular shape [pic]. The second can has a small black mark on the bottom but I'm not sure that means anything. Otherwise the cans appear fine, no other bulges, no visible punctures, the cans feel full and as heavy as a normal can.

What would cause this? I've heard of cans bulging after they're frozen but not just on the bottom. And I think it's unlikely they were frozen at any point, since this is June in North Carolina and they weren't even bought cold, let alone frozen. They haven't even been stored in the fridge.

If I open them will they explode? Spray botulism spores all over me? Could I drink them?
posted by katyggls to Food & Drink (12 answers total) 3 users marked this as a favorite
Best answer: I wonder if the case was dropped? That might have caused a downward pressure that caused the bottom to buckle?
posted by roboton666 at 4:02 PM on June 20, 2011

Best answer: The cans were dropped. I drink 'em.
posted by wierdo at 4:02 PM on June 20, 2011

Freezing and botulism aren't the only things that can dent cans from the inside. I doubt it would be botulism, both because of the preservatives and the acidity of soda.

The first thing that comes to mind for me is pressure changes during shipping. This can happen with ground shipping, if there are elevation differences along the route. I know from personal experience that if you take soda cans to high enough elevations, they will explode.

My advice would be to open them carefully, but that they are probably safe to drink. Of course, don't drink it if anything smells off!
posted by Gneisskate at 4:07 PM on June 20, 2011

Dying? Explosions? Botulism?

The can has taken a knock and is slightly misshapen.
posted by fire&wings at 4:08 PM on June 20, 2011

Best answer: 'nthing they were accidentally dropped during shipment...happened to a few in a case I dropped just last week (one of them ruptured, the rest just popped their bottoms like the ones in your pic). I'm thinking it's due to the sudden shock where carbon molecules disperse from the liquid and build up gas pressure...try shaking a 2 litre soda bottle sometime and you'll notice it gets rock hard...nothing to worry about, just let them settle for an hour and they'll recarbonate and should open fine with no explosions. You can also tap on the lid a few times before opening just in case.
posted by samsara at 4:14 PM on June 20, 2011

One other possibility could be that they froze or got super hot at some point, both could cause a pressure increase that pushed the bottom out (if I let a soda can freeze by accident it does exactly this). I'm not a food scientist, but I'm pretty sure soda is too acidic for botulism to ever be an issue.
posted by crabintheocean at 4:47 PM on June 20, 2011

They just got shaken up at some point. Maybe the truck hit a pothole or something.. Thin gauge aluminum is no match for pressurized carbon dioxide.
posted by Sys Rq at 5:18 PM on June 20, 2011

Botulism swells cans because it causes a buildup of pressurized gas inside them. Fizzy drinks come with pressurized gas inbuilt. The bottoms of fizzy drink cans are indented to resist that pressure, but sometimes get exposed to conditions that mean resistance is useless.
posted by flabdablet at 5:38 PM on June 20, 2011

This might be confirmation bias, but I have noticed similar things happening to canned soda in my possession. I had several cans in a case of Diet Pepsi explode in the trunk of my car after being left there in the heat (ewwww big mess, and several of the non-explodey cans bulged on the top and bottom.

I also had other cans of Coke and Sprite similarly deform after being left in my car. You'd think I'd learn.

I can't recall this happening with any frequency in previous years, so it may reflect some change in manufacturing process. Or confirmation bias. Take your pick.
posted by QuantumMeruit at 6:02 PM on June 20, 2011

Response by poster: Thanks all. I'm going to go with the dropped explanation because it seems to make the most sense given that the bulging is only happening on the bottom of the cans. I took them outside and opened them just in case they sprayed everywhere (not because I was afraid of getting sprayed by poisonous pop but because I wanted to avoid cleaning soda off the floor) but they opened just fine, and the soda smelled ok and everything so I drank it. It tasted fine and as of right now I'm alive and well. :)
posted by katyggls at 7:37 PM on June 20, 2011

If you take a case of beer/pop and drop it flat onto the ground, the bottoms of all the cans will bulge like that. (I did NOT learn that as a youth, restocking vending machines.)

The bottoms of pressurized beverage containers are curved upward to try to resist this, because a flat bottom would want to pop off at the slightest nudge. A spherical container is the strongest, assuming the material is the same thickness, but that's not convenient. (Remember the old 2-liter bottles with the plastic cap on the bottom? They solved that by figuring out how to make the bottom of the bottle stronger/thicker.) So for cans, they just invert the sphere.
posted by gjc at 5:31 AM on June 21, 2011

Oh, and why it happens regularly these days, but 10 to 15 years ago it almost never happened? They use less aluminum now. Apparently, they've gotten down to about the thinnest practical can.
posted by wierdo at 11:29 AM on June 21, 2011

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