So this entry is a tribute to one of my very good friends (shout out Kara) who had a very interesting experience trying to make popcorn without an air popper or a microwave. It is also one in a series of posts about how to eat foods without artificial preservatives (see jam and hamburger helper). My goal for this summer is to cut my artificial preservatives down to an absolute minimum. And that makes snack food a little tricky. But, popcorn from something other than a bag is actually pretty good and low calorie, so it has become a staple in my snack food diet, and a mystery. How does popcorn work?
Popcorn is a seed. There are three main things in a popcorn kernel, the shell, the starches inside (to feed an eventual popcorn plant), and some water. Before you heat it everything is contained inside the hard shell. But, as you heat the kernels the water turns to steam (a gas) and the volume remains constant while the temperature increases, increasing the pressure (remember P*V=n*R*T?). Eventually the pressure is just too much for the little shell and BOOM, it pops open like a balloon with too much air in it. The starches stretch out and form a solid network through covalent bonds, trapping air as it goes (see cornstarch crystal). When air is dissolved in a solid it is a colloid known as solid foam, like styrofoam.
Because of how it works popcorn will not pop if 1) the popcorn doesn't get hot enough (which is why you cook it in hot oil), 2) the popcorn dries out, or 3) if the popcorn shell has a crack or hole in it that releases the steam, lowering the pressure.
A microwave works by sending out a frequency in the electromagnetic spectrum (like the light we see, the UV rays that hurt our skin, or the radio waves that make beautiful music). The frequency it uses is a very special one that makes the bonds in water jiggle and dance (resonance). Temperature is a measure of how fast the molecules are moving, so as they dance more, the temperature goes up and eventually the dance so far away from each other the create steam, increased pressure, and eventually a popcorn explosion.
If you don't have a microwave you have to use a lower tech version to make the water dance, heat transfer. As molecules from something warmer, like hot oil, hit slower moving molecules from something colder, like the water in the popcorn, a little bit of the speed is transfered. Making the hot thing colder and the cold thing hotter until they are the same temperature. It's like when you play pool. When one pool ball hits another the first one slows down and the second one starts moving or speeds up. Molecules act the same way.
This is not really a recipe, but directions for how to make popcorn yourself without any special gadgets. Enjoy!
Ingredients
2 Tablespoons oil
1/4 cup unpopped popcorn kernels
Toppings of your choice
Place oil in a sauce pan with a single kernel of popcorn. Heat on medium until the kernel pops. Add remaining popcorn kernels and cover with a lid. Heat, shaking frequently, until the popping slows to 2-3 seconds between each pop. Remove from heat, cover in toppings and enjoy.
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