DEFY S. McQUAID! #70: Bad, bad soda

The Question

Jon Abad asks:

Does soda go bad?

I just got a Mountain Dew out of the coke machine and there is a “For Best Taste, Drink by this date” thing on the side like with certain american beers.

So my question to the all powerful Oz (aka McQuaid) is can soda go bad while its in the can? What’s its shelf life? Will it outlive us all?

The Answer

Yes —– and no!

First off, the ingredients in soda are generally water, carbon dioxide, sugar (or sugar replacement), and flavoring. Luckily, none of these will “go bad” in the traditional sense (microorganisms taking over the can and poison the drinker).

Let’s look at the ingredients individually and see what we can see.

– WATER
Water will not go bad. And since the can is sealed, it won’t evaporate. No problem here.

– CARBON DIOXIDE
The carbon dioxide WILL eventually percolate out of the can through osmosis. This means that eventually, the soda will go flat. Does this constitute “going bad”? I think not – the soda is still consumable, you just may not want to. This could indicate why the “best taste by” date is given on your can of Mountain Dew.

– SUGAR
Usually a growth medium for everything, the sugar in the can is protected by being vacuum sealed in, and by being in solution. Shouldn’t be a problem here. BUT….

– SUGAR SUBSTITUTE
Aspartame is under fire by certain groups who state that it breaks down into methanol and formaldhyde in the small intestine, and that is unhealthy. While it is undisputed that this occurs, some state that the levels are not toxic, since alcoholic beverages do the same thing. There is evidence both ways.
In any case, the argument is that the aspartame decomposes into methanol and formaldhyde if left in a metal can for too long. This probably ruins the taste of the soda if it does occur.

– FLAVORING
The flavoring components are usually matched with preservatives, so there’s no chance of them causing the soda to go bad.

In summary, I’d believe the label – for best TASTE, drink before the date on the can. Otherwise, the soda may be flat, taste too much like the can (from slowly eroding aluminum molecules away), or be otherwise compromised.

18 thoughts on “DEFY S. McQUAID! #70: Bad, bad soda

  • 6/20/2006 at 8:04 am
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    There’s no sugar in modern soda… High Fructose Corn Syrup is the sweetner of choice. Gross.

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  • 6/20/2006 at 9:17 am
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    Depends where you are. Here in the UK my Coke contains actual sugar :)

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  • 6/20/2006 at 9:24 am
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    CO2 “percolating” through solid aluminium? I don’t think osmosis works that way. Osmosis is a liquid passing through a semi-permeable membrane. CO2 isn’t a liquid (not at room temp, anyway) and solid aluminium is not a semi-permeable membrane.

    CO2 dissolved in water is acidic though, I wonder how long it would be before it ate through the can?

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  • 6/20/2006 at 1:13 pm
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    The eroded aluminum, however, is very bad for you. Unless, of course, you want Alzheimer’s.

    You sort of glossed over that point.

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  • 6/20/2006 at 4:40 pm
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    I glossed over a number of points…like the fact that the methanol and formaldyde will damage your body in addition to tasting bad, and that eroded aluminum will do the same, etc. There were a number of tongue-in-cheek references here.

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  • 6/20/2006 at 4:46 pm
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    And yet the gas escapes from the can, eventually. Leave it long enough, and it will find a way out. Soda cans are not hermetically sealed.

    However, I grant you that it will take a lot longer for a can of soda to go flat than a plastic bottle – since plastic is a lot more permeable.

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  • 6/20/2006 at 4:47 pm
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    There are a few bottling plants around the U.S. that still use sugar as well. But you are correct – the majority of American Coke is sweetened with high fructose corn syrup – fructose being a sugar, by the way (if not “sugar” in the usual sense).

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  • 6/20/2006 at 4:48 pm
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    And at whole foods, I get my favorite soda, which has Sugar Cane!
    My second favorite is Coke Zero which has aspertame but no HFCS.

    In the long term, I actually trust aspertame more than HFCS.

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  • 6/20/2006 at 4:50 pm
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    I put money in and Mountain Dew comes out. None of this Mount Dew that you refer to.

    And I’m 99% sure that its a Coke machine. I remember lots of red.

    I imagine that they’re like “software developers are gonna work on this floor? mt dew it is!”

    I don’t think Jolt comes out of machines anymore…

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  • 6/20/2006 at 4:52 pm
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    So in conclusion, don’t plan on using soda cans for long term storage in your bomb/hurricane/toddler shelter.

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  • 6/20/2006 at 5:46 pm
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    I’ve succesfully cut HFCS out of my det 100%, and aspartame never entered it… since it does funky things to me. Occasionally I drink something with splenda, but for me it’s usually Sugar Cane or bust.

    I get my caffeine from 3-4 cups of coffee a day, black no sugar. mmmmm.

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  • 6/21/2006 at 7:59 am
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    I find it hard to believe that a pepsi product would be found in the dirty, dirty belly of a coke machine. Bah!

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  • 6/21/2006 at 4:02 pm
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    I believe that the word Shaun was looking for was diffision or even effusion, not osmosis, and it occurs whether we like it or not. Also, Soft drink cans are lined with an epoxy resin to prevent the beverage from “eating” through the aluminum can. This should slow it down, but not prevent it.

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  • 6/2/2008 at 6:49 pm
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    Soft drink cans are indeed lined from epoxy resin which also gives the freshness expiry date a long life span.

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  • 6/3/2008 at 11:43 am
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    Thanks Aaron. Always nice to see some action in the Defy Archives…

    Reply

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