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Are stale bagels better insulators than fresh ones?

  1. Oct 29, 2011 #1

    cmb

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    It may be my imagination, but if I toast a fresh bagel it comes out of the toaster hotter than one that has been kicking around the kitchen for more than a week.

    I tend to blob butter on it and let it melt before smoothing it over, rather than putting effort into 'spreading' cold butter (plus avoiding squishing your nicely toasted bread).

    The butter on the fresh one melts quick, whereas the butter on the stale one needs a bit of spreading and doesn't all seem to melt. The stale one just doesn't seem to get as hot as the fresh one.
     
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  3. Oct 29, 2011 #2

    I like Serena

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    My first guess would be that the stale one has absorbed moisture from the air.
    It takes more energy to heat it.
     
  4. Oct 29, 2011 #3

    xts

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    Stale one (yuck!) is much dryer - it contains quite a little moist. So even if it is hotter (by means of temperature) it has very low heat conductivity and small heat capacitance.

    On the other hand, the fresh one if toasted, contains lots of water at temp close to 100C - it provides additional heat capacitance and heat transport, as water evaporates and condenses back on butter (or your fingers).

    Moist toast at 95C may seems much hotter than dry one at 120C.
     
  5. Oct 29, 2011 #4
    I wonder how you are able to do that! :confused:
    stale bread is drier, but staling is not only a process of evaporation: if it were so it would be faster in moist environment and at room temperature. (Bread stored in the refrigerator stales quicker): starch molecules are degelatinized, the consequences of this process are not known but might be relevant. Then again, stale bread toasts quicker: if the timer is not regulated, this will make things worse, there will be no moisture left.
    Water evaporating from toasted fresh bread is hotter, moves faster. More moisture = more heat: more heat at higher temp moving faster.
     
    Last edited: Oct 29, 2011
  6. Oct 29, 2011 #5

    xts

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    A little bit off topic, but I am curious: is it (where? what culture?) popular to toast bagels?
     
  7. Oct 29, 2011 #6

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    Huh? :confused:
    Is this true?

    I thought everything happens slower when it's colder.
     
  8. Oct 29, 2011 #7

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    OK, so the first bagel I had earlier was the last of 5 bought about 9 days ago. They were supermarket types that have some preservative chucked in them to keep a bit longer. It wasn't 'dried out', just not as fresh as you might want but good eough for toasting. It had been wrapped in its plastic bag for that week.

    The thing about the fresher one being 'more humid' is a clear difference but I was thinking that maybe this means there is less 'contiguity' between the structures of the bread, so does not conduct heat so fast into its interior. The higher humidity might have equally meant it was cooler, as that would have the opportunity to evaporate and lower the temperature (like the fire brigade recommend putting a wet blanket over you if you have to run out of a burning building), but this evaporation process doesn't seem to be the mechanism that wins out. Rather, the moisture seems to aid conduction into the bagel so that the heat gets deeper into it.

    I guess an experiment could be done the next time I have both fresh and old packets - I can microwave a test piece. That way, they should heat internally. Not sure how the change of water content might impact that, though. I have an IR thermometer, I'll do some tests sometime and report back some objective values .....
     
  9. Oct 29, 2011 #8

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    I think that's true also. My wife has kept bread in the fridge before, and it is disgusting afterwards. Bread is OK if you freeze and unfreeze it quick, but it goes baaad if it dwells too long at that ~4°C range.
     
  10. Oct 29, 2011 #9
    Rrefrigeration will slow the growth of mold and other undesibables, but it does stale faster in the refrigerator, than on the kitchen counter. I you want to keep bread for a longer time it would be best to freeze the loaf.

    A bread going stale undergoes a chemical process as you have said. Most of the moisture is still in the bread. Evaporation would result in a crispy, crumbly bread instead of the tough stuff when it stales.

    To un-stale, reheat the bread and the chemical process is reversed somewhat. The evaporated parts will still be dry though. You have to eat the re-heated bread right away before it cools.

    Edit: By the way, stale bread is used in many culinary dishes such as French toast and croutons.
     
    Last edited: Oct 29, 2011
  11. Oct 29, 2011 #10
    Yes, it is true, it is not "evaporation". There is enough moisture in stale bread, but it is not "available", it is strange, but you get it back by heat. You can check it yourself : if you warm a stale roll "gently" up to 65 C°, it becomes crisp againg, instead of getting worse. Starch molecules re-gelatinize!.
    No insulation.
     
    Last edited: Oct 29, 2011
  12. Oct 29, 2011 #11
    When re-heating, it is best to put the bread inside a moist paper bag.
     
  13. Oct 29, 2011 #12

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    Actually, I'm used to freezing fresh bread immediately.
    If found that even the next day, reheating with a microwave tastes better than bread kept at room temperature.
    Have to eat it immediately though.
     
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