Why All Kernels Don’t Pop Into Popcorn?

Before answering the question in the title, first we need to understand how corn kernels turn into popcorn. The casing of the kernels are called hulls or husks which are supposed to be waterproof. However inside the kernel there is a small amount of water and plenty of starch.

When we heat up the kernels, the water begins to evaporate and the starch inside gets cooked due to the temperature and pressure. The evaporation of the water causes its expansion and the pressure builds on the husks. At one point the husks can’t take it anymore and explodes and the cooked starch comes out in the form of popcorn that we all love.

So what happens to the kernels that don’t pop? Well, they had a leak and the water could not be trapped inside to evaporate and expand. Instead it leaked out. The starch on the inside does cook but since the husks don’t burst open it stays inside. And thus, those kernels will never pop.