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Why do noodles make the soup boil?

  1. Dec 7, 2008 #1
    When the soup is heated close to the boiling point and one puts noodles inside, it boils over (even if it is put away from the fire). Does anyone know why?
     
  2. jcsd
  3. Dec 7, 2008 #2
    I don't know. I have made plenty of spaghetti during my life, and whenevr I add the pasta to the boiling water, the boiling temporarily stops. It seems to me that adding anything to boiling water will stop the boil until it heats up again.
     
  4. Dec 7, 2008 #3

    mgb_phys

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    It's called superheating.
    You can gently heat a liquid slightly past it's boiling point if there is nothing to start the bubbles forming. Add something with lots of surface area, especially the powder on packet noodles or sugar to coffee and suddenly there are lots of nucleation sites for bubbles to form on.
    You can also do the same thing with freezing. If you cool ultra pure water below it's freezing point then tap the side of the container you can make the whole volume freeze instantly

    It's a big danger if you make drinks in the microwave - the water can be quickly heated well past it's boiling point and then as soon as it is disturbed by you moving it or putting in a spoon it will instantly boil over your hand. It's rarer in a pan on a stove - you normally make pasta with water that is a roiling boil.
     
  5. Dec 7, 2008 #4
    Yeah, I've seen that with noodles. Rice will do it(overboil) too.
    I wonder if the starch has anything to do with it.
    In any event I've noticed that the overboil bubbles in those cases seem to have a cloudy film on them. Probably like mgb was saying.
     
  6. Dec 7, 2008 #5
    If anything I would think that the noodles would lower the emperture because you are adding something room temperature to something hot. Its possible that the noodles would raise the volume of the water causing it to overflow when it boiled.
     
  7. Dec 7, 2008 #6

    FredGarvin

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    The boil over is usually due to starches in the noodles being released into the boiling water. If you want to avoid the foam issue, try using much MUCH more water for boiling than you currently use.
     
  8. Dec 8, 2008 #7
    I would agree. The starches released causes the boiling bubbles to be en-coated in a thin film... thus allowing the bubbles to grow much larger before "popping"; hence boil over.

    In practice, one usually raises the pot from the burner, reduce the temp of the burner by dialing down a notch or two, wait a few seconds, then replacing the pot on the burner. Voilà!
    The food still boils, but no more pesky boil over.
     
  9. Dec 8, 2008 #8

    Danger

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    I don't know much about cooking (so this might wreck your food), but you could also just add the noodles to the water before it boils, as I do with eggs.
    Also, water doesn't get any hotter no matter how much you boil it. Once it's bubbling, you can turn the heat down just enough to maintain a simmer. That's still at the boiling point, but doesn't cause excessive bubbling. (It can also save on your utility bill.)
     
  10. Dec 8, 2008 #9

    Dale

    Staff: Mentor

    I agree. I understand the principle of superheating, but I have never observed it on my stove.
     
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