• Question: What makes pop corn pop?

    Asked by aileenjcat to Colin, John, Kevin, Shikha, Triona on 12 Nov 2014.
    • Photo: Tríona O'Connell

      Tríona O'Connell answered on 12 Nov 2014:

      I love popcorn and watching it pop (I make it in a pot with a clear glass lid, very exciting until the steam builds up).
      The skin on the outside of the popcorn kernel is very strong and can withstand high pressure. As you heat the popcorn, the small amount of water that is inside the kernel begins to expand, eventually the amount of expansion the water is trying to do is greater than the pressure the skin can withstand and there’s a catastrophic failure of the hull. The escaping steam then brings the heated insides with it (that have also been expanded, like a foam) and it cools quickly with the drop in pressure and forms teh popcorn kernel we all know and love (and hate to pick out of our teeth)

    • Photo: Shikha Sharma

      Shikha Sharma answered on 20 Nov 2014:

      Hi aileenjcat,

      Popcorn kernels contain oil and water with starch, surrounded by a hard and strong outer coating. When popcorn is heated, the water inside the kernel tries to expand into steam, but it cannot escape through the seed coat. The hot oil and steam gelatinizes the starch inside the popcorn kernel, making it softer and more pliable. When the popcorn reaches a temperature of 180 °C the pressure inside the kernel is around 135 psi, which is sufficient pressure to rupture the popcorn hull, essentially turning the kernel inside-out. The pressure inside the kernel is released very quickly, expanding the proteins and starch inside the popcorn kernel into a foam, which cools and sets into the familiar popcorn puff. 🙂

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