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Why does water taste stale after sitting out?

  1. Aug 11, 2011 #1
    Why does water taste stale after sitting out overnight?

    Some suspicions I have...
    1) Dust settling, and that "stale" taste is dust.
    2) Microorganism/bacteria enter and multiply (especially because I drank out of it yesterday, which I suppose would be an easy hypothesis to test... fill the cup but don't drink from it, then wait a day and drink it).
    3) It's from a plastic cup, so perhaps a small amount of plastic has leached into the water.

    I read an answer on answers.com or somewhere and someone said it is because the aeration of the water which has gone away after sitting.
     
  2. jcsd
  3. Aug 15, 2011 #2

    Borek

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    Unless water was pressurized or cold amount of gas dissolved is the same no matter how long the water was sitting open. Unless we are talking about carbon dioxide, but that's not aeration.
     
  4. Aug 15, 2011 #3
    Well, the water would have been slightly pressurized... (~50psi?) Also, the water is likely be below room temperature (either when it comes out of a tap or out of the fridge), so it would warm up to room temp.... I just don't know if the relatively slight difference in temperature would be enough to changed dissolved gases... Water definitely has gasses/air in it because that's why ice freezes white... right?
     
  5. Aug 15, 2011 #4
    Would the water absorb different orders in the air?
     
  6. Aug 15, 2011 #5

    Borek

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    Solubility of the gases changes with temperature (goes down when temperature goes up). Cold water loses gas when heated, but it happens quite fast, you don't have to wait whole night.
     
  7. Aug 16, 2011 #6

    Fra

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    There are probably different factors but I definitely think SOME plastics, really do give flavour to water at least according to my experience. I think PE and PP plastics in particular. PET probably less so. If you doubt it, do a side by side comparasion, put water in a glass bottle vs PE and leave it for a day and do a blind test. If you think it's the air you can leave it withe th can open.

    I know this from experience with brewing, and in particular heating the water in the plastic magnifies the effect, but it's there anyway. But it's most easily detected not in flavour but in the aroma. One can easily sense the smell of plastic in the water.

    Still not sure what the molecules are though but it's certainly not the PE plastic polymers itself you can smell. But at least some plastics can degrade to a range of compounds including aldehydes with extremely low odour tresholds, so my hunch is that plastic does matter and while the concentration is most probably no health issue the odour tresholds of some compounds are really low. Some the order of ppb.

    /Fredrik
     
  8. Aug 16, 2011 #7
    Thank you for the replies! I definitely will test the plastic theory... It is hdpe.

    But, back to the gasses... I'm not referring to "dissolved" gasses as much as I am microscopic air bubbles, which maybe goes back to why ice is white... Just like occasionally you'll see this from a tap, makes the water look white or cloudy for a minute or so... But if the bubbles were "much" smaller, perhaps it takes much longer to come out...
     
  9. Aug 17, 2011 #8
    Did you know that the main purpose of the small "filter" where the water comes out of the tap isn't there to filter out the water? It's there to introduce gasses into the water... to make it taste better. Weird huh?

    This is probably why it tastes stale after its left out overnight ;)
     
  10. Aug 17, 2011 #9

    Borek

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    Any reference for that? My understanding is that it is there to mix water with air so that you get a better stream using less water - effectively lowering water use. Nothing to do with water taste.

    http://en.wikipedia.org/wiki/Faucet_aerator
     
  11. Aug 17, 2011 #10

    Fra

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    I could also be that when you wake up in the morning to take a sip, you forgot to brush your teeth before you went to bed. Also if you was drinking alcohol the night before everything tastes a little bit stale the morning after ;)

    I just noted this since I've tried hard to sample and evaluate lots of stuff from brewing and a big fuzz factor that renders evaluations less reproducable is exactly what you drank or ate before the sampling. Even your own breath can influence the aroma of a beer.

    Many many hours after drinking alcohol, any class of water can taste of funky aldehydes if you are sensitive. I think I read somewhere (a paper) where it was even confirmed that bacteria in your mouth can oxidise the beer pretty much at a time scale it takes to drink it, just at a sufficient rante to sometimes produce compounds above the treshold. So your bacterial culture in the mouth will impact anything you taste or eat or drink.

    /Fredrik
     
  12. Aug 17, 2011 #11
    I was having a chat to my chemistry teacher about this topic and he told me this. He is explinations made sense and he is one of the most intellgent people I've met.
     
  13. Aug 17, 2011 #12

    Borek

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    As a reference it is worth even less than the wikipedia article I linked to. Fact that water usage goes down was researched and published - William DeOreo et al., “Retrofit Realities,” Journal AWWA (March 2001), but to be honest I am not sure if JAWWA is peer reviewed or not. See forum rules to learn what is meant by "reference" at PF.
     
  14. Aug 17, 2011 #13

    DaveC426913

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    It would be pretty trivial to eliminate this as a variable. Make the comparison between old water and fresh water simultaneously (i.e. in the morning). Don't try to compare two subjective experiences separated by 8+ hours.
     
  15. Aug 18, 2011 #14
    I'm sorry I don't follow :confused:

    But, if there isn't a book or article published on it... I can't mention it on these forums?
     
  16. Aug 18, 2011 #15

    Borek

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    You can't state it as a fact.
     
  17. Aug 18, 2011 #16
    What if it's on a TV or Radio show? There are many facts that I hear over the radio, stuff that I can't find online :smile:
     
  18. Aug 18, 2011 #17

    Borek

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    In general they don't qualify. Once again - please read forum rules.
     
  19. Aug 18, 2011 #18

    DaveC426913

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    Generally speaking, we have a tighter definition of what constitutes factual. There's nothing wrong with saying "I heard this from this source, is it true?" but you should state the source, and we will reserve the right to challenge the veracity of the claim to be backed with reliable sources.
     
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