• Question: What makes popcorn pop?

    Asked by andrealafuente to Ceri, Marikka, Matt, Rob on 19 Nov 2014.
    • Photo: Ceri Dare

      Ceri Dare answered on 19 Nov 2014:

      I don’t know, but this seems like a sensible explanantion: http://www.popcorn.org/ForTeachers/TeachingGuide/WhatMakesPopcornPop/tabid/88/Default.aspx

    • Photo: Marikka Beecroft

      Marikka Beecroft answered on 19 Nov 2014:

      In each popcorn kernel there is water and starch surrounded by that horrible part of the popcorn that you get stuck in between your teeth (I don’t know the name of it!!). When you heat the popcorn up in a microwave the water heats up and turns into steam but because the steam is now so hot it cooks the starch and this causes the popcorn to pop! There is just too much pressure inside that it explodes out a little bit like a bomb. I learned about this at A-level biology and we had some lovely popcorn after the demonstration!

    • Photo: Robert Hampson

      Robert Hampson answered on 20 Nov 2014:

      I did not know the answer to this. I have thought about it many times.

      I understand the steam popping the kernel (the outside shell thing) because that’s just like a steam engine.

      I never got where all the stuff comes from though. I know people say its the starch that’s been cooked and it expanded, but a potato is filled with starch and it doesn’t expand when you cook it (or at least if it does it is not as much as popcorn!) There must be something different about the starch.

      The closest thing I can think of is the stuff that makes prawn crackers. They start off really small and then when you heat them really hot in oil they expand a lot.

      I suppose the shell could keep the steam under pressure allowing it to get really hot (which doesn’t happen when you cook a potato) and then have the same kind of reaction as the prawn cracker starch. Then because of the pressure from the steam and the starch the kernel pops releasing the expanded starch everywhere…

      That sounds like a convincing explanation. I don’t know if it is right though. I never studied it, maybe I should do some experiments!

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