Results 1 to 13 of 13

Thread: Picnic time

  1. #1
    Plutonium Lounger
    Join Date
    Mar 2002
    Posts
    84,353
    Thanks
    0
    Thanked 29 Times in 29 Posts

    Re: Picnic time

    <span style="background-color: #FFFF00; color: #FFFF00; font-weight: bold">-5 degrees Celsius isn't enough to stop bacterial activity. Bacteria continue to digest the meat and as a by-product, produce gas (carbon dioxide? methane?)</span hide>

  2. #2
    Platinum Lounger
    Join Date
    Feb 2002
    Location
    A Magic Forest in Deepest, Darkest Kent
    Posts
    5,681
    Thanks
    0
    Thanked 1 Time in 1 Post

    Re: Picnic time

    This could be one of the answers so you can have half a [choccy bar] for this fine effort.

    There is another <span style="background-color: #FFFF00; color: #FFFF00; font-weight: bold">non-bacterial</span hide> answer which I was looking for as well <img src=/S/snow.gif border=0 alt=snow width=32 height=32>
    Jerry

  3. #3
    Platinum Lounger
    Join Date
    Nov 2001
    Location
    Melbourne, Victoria, Australia
    Posts
    5,016
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Re: Picnic time

    I will hazard a guess, which I suspect will be wrong:
    <span style="background-color: #FFFF00; color: #FFFF00; font-weight: bold">Most plastic films are permeable to air, but not to water. The moist air trapped within the bag and the dry air in the freezer represent a moisture concentration difference. This means that moisture will try (without success) to move from within the bag into the freezer atmosphere, while air will try (successfully) to move from the freezer atmosphere, into the bag. The bag will therefore inflate. </span hide>

    I'd say it's wrong because <span style="background-color: #FFFF00; color: #FFFF00; font-weight: bold">I doubt the diffusion rate would be at all significant at -5

  4. #4
    Platinum Lounger
    Join Date
    Feb 2002
    Location
    A Magic Forest in Deepest, Darkest Kent
    Posts
    5,681
    Thanks
    0
    Thanked 1 Time in 1 Post

    Re: Picnic time

    Good thinking

    I did mention that the plastic wrapper was hermetically sealed ( <img src=/S/whisper.gif border=0 alt=whisper width=29 height=17>Althought I spelt it wrong in the original post)

    <span style="background-color: #FFFF00; color: #FFFF00; font-weight: bold">You are on the right lines to do with air movement though...but not from the outside of the wrapper</span hide>
    Jerry

  5. #5
    Platinum Lounger
    Join Date
    Feb 2002
    Location
    A Magic Forest in Deepest, Darkest Kent
    Posts
    5,681
    Thanks
    0
    Thanked 1 Time in 1 Post

    Picnic time

    <P ID="edit" class=small>(Edited by Jezza on 06-Mar-06 11:33. To change a misspelt word)</P>Jezza Bear went to the forest butchers the other day and bought some juicy turkey-breast cold cuts that were to be eaten on the family picnic. On his way back to the log cabin Wise Old Olly Owl advised him that as the picnic was some days away he should put them in the freezer.

    Jezza Bear being a keen cook sealed the cold cuts in some plastic film (hermetically sealed) and placed them in the freezer (-5 degees C). A few days later, the night before the picnic, Jezza Bear went to the freezer and to his amazement found the the packaging around the turkey cuts had blown up like a balloon, inflated to twice its size and filled with a clear gas. What could have caused this bloating?

    PS---True scenario
    Jerry

  6. #6
    Plutonium Lounger
    Join Date
    Nov 2001
    Posts
    10,550
    Thanks
    0
    Thanked 7 Times in 7 Posts

    Re: Picnic time

    So was this the last dying exhalation of the poor wrapped fowl?

    StuartR

  7. #7
    Platinum Lounger
    Join Date
    Feb 2002
    Location
    A Magic Forest in Deepest, Darkest Kent
    Posts
    5,681
    Thanks
    0
    Thanked 1 Time in 1 Post

    Re: Picnic time

    <img src=/S/nope.gif border=0 alt=nope width=15 height=15>
    Jerry

  8. #8
    Platinum Lounger
    Join Date
    Nov 2001
    Location
    Melbourne, Victoria, Australia
    Posts
    5,016
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Re: Picnic time

    The spelling would be of no consequence to the validity of my argument. <img src=/S/grin.gif border=0 alt=grin width=15 height=15> Although the whole idea of <span style="background-color: #FFFF00; color: #FFFF00; font-weight: bold">hermetically sealing a semi-permeable membrane</span hide> might need a bit of qualification. Your hint did generate another idea though: <span style="background-color: #FFFF00; color: #FFFF00; font-weight: bold">as the meat froze, the solubility of the disolved gases decreased, causing their (gaseous) release into the confines of the bag.</span hide>

    Alan

  9. #9
    Platinum Lounger
    Join Date
    Feb 2002
    Location
    A Magic Forest in Deepest, Darkest Kent
    Posts
    5,681
    Thanks
    0
    Thanked 1 Time in 1 Post

    Re: Picnic time

    <img src=/S/bananas.gif border=0 alt=bananas width=33 height=35>
    The official New Scientist answer is:


    <span style="background-color: #FFFF00; color: #FFFF00; font-weight: bold">Jezza Bear's buthcer has sold him not just turkey but some water with air dissolved in it. At just above freezing point (The temp. you would expect in a butchers display cabinet) the water will dissolve the maximum amount of atmospheric gases ( mainly oxygen and nitrogen). When Jezza Bear subsequently froze the meat in his freezer this dissolved air was pushed out by the advancing ice crystals.

    This does not occur in flash-frozen meats as the air does not have time to escape.</span hide>

    Have a [choccy bar] and some [delicious turkey relish]
    Jerry

  10. #10
    Platinum Lounger
    Join Date
    Nov 2001
    Location
    Melbourne, Victoria, Australia
    Posts
    5,016
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Re: Picnic time

    I find the "<span style="background-color: #FFFF00; color: #FFFF00; font-weight: bold">this dissolved air was pushed out by the advancing ice crystals</span hide>" to be rather "unscientific", from New Scientist. It's really a matter of <span style="background-color: #FFFF00; color: #FFFF00; font-weight: bold">kinetics, associated with the cooling rate. At higher cooling rates, the air doesn't have time to come out of solution, as a gas. By similar argument, if the cooling rate is rapid, high nucleation rates of ice crystals occurs, so the end result is a very fine structure of minute crystals, rather than fewer coarse ones. i.e. lots of nucleation and little growth.</span hide>

    I mention this latter aspect because the research establishment I worked for was once approached by an IVF program, to try to figure out how to rapidly freeze an embryo over a critical temperature range in which ice crystals form. The problem apparently was that the growth of crystals was damaging/ destroying the cell. From memory, it was several hundred

  11. #11
    Platinum Lounger
    Join Date
    Feb 2002
    Location
    A Magic Forest in Deepest, Darkest Kent
    Posts
    5,681
    Thanks
    0
    Thanked 1 Time in 1 Post

    Re: Picnic time

    > be rather "unscientific", from New Scientist... <img src=/S/yep.gif border=0 alt=yep width=15 height=15>

    I read it in "Last Words" on the back page...a link is here: Bloated fowl
    Jerry

  12. #12
    Platinum Lounger
    Join Date
    Nov 2001
    Location
    Melbourne, Victoria, Australia
    Posts
    5,016
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Re: Picnic time

    That's interesting though. It's suggesting that once the air comes out of solution, there's a need to physically "push" the bubbles out of the meat structure. I hadn't thought of that one (I thought only of the water component). Sounds feasible though. I wonder if the effect could be seen freezing a sealed up ice cube tray?

    Alan

  13. #13
    Platinum Lounger
    Join Date
    Feb 2002
    Location
    A Magic Forest in Deepest, Darkest Kent
    Posts
    5,681
    Thanks
    0
    Thanked 1 Time in 1 Post

    Re: Picnic time

    Yes...maybe a KTS project to think about....kind of similar to <!post=Another 'Science' Question,553928>Another 'Science' Question<!/post> posted by <!profile=Rebel>Rebel<!/profile> a while back
    Jerry

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •