Popcorn: it's equally fun to make and to eat. But just what makes each kernel pop the way it does and what is the ideal temperature for popcorn to pop at? A new study answers all these questions.
"Popcorn is the funniest corn to cook, because it jumps and makes a 'pop' sound in our pans," begin the researchers in their new article in the Journal of the Royal Society Interface. Indeed! But the knowledge about to dropped has only just begun, as the researchers explain that though the basics of popcorn popping are understood, the precise mechanics of the process remain shrouded in mystery:
When the popcorn temperature exceeds 100°C, its water content (moisture) boils and reaches a thermodynamic equilibrium at the vapour pressure, as in a pressure cooker. Above a critical vapour pressure, the hull breaks. At the same time in the popcorn endosperm, the starch granules expand adiabatically and form a spongy flake of various shapes, as shown in the insets of figure 1. Then, the popcorn jumps a few millimetres high to several centimetres high and a characteristic 'pop' sound is emitted. To the best of our knowledge, the physical origin of these observations remains elusive in the literature.
To get a better idea of how the process works, the researchers undertook three basic research methods: 1) popping kernels at slowly escalating heats 2) dropping individual kernels on a hot plate and recording the process with a high speed camera 3) recording individual "pops" with a microphone and measuring the acoustics.
So what did the researchers find? Interestingly, there's a commonality between the ways that a gymnast might somersault through the air and popcorn. When heated, a flake extends outwards from the kernel; this flake grows quickly, turning into a "leg" that the now exploding kernel propels off of. The scientists were also able to zero in a temperature most likely to result in the fewest unpopped kernels. The heat test revealed that 96% of all kernels will pop at 180°C.
Image: mama_mia / shutterstock.