Last year, Patty Brennan and I were part of the SciFund Challenge – an experiment in crowdfunding scientific research that raised over $75,000 for its projects in just 45 days. RocketHub, our hosting platform, clearly took note: it added “Science” to its overall list of project categories, so appeals to support dance, music or photography will now sit alongside requests to fund projects in plant genetics or primatology. And I was delighted to learn that one of the first scientists to step up to the plate is doing some fantastic functional morphology.
He’s already raised enough cash to fund his experiments in South Africa, but further donations will let him take the study to other countries. His RocketHub link is <here>, and there's still a couple of weeks left to donate.
I just learned that one of my photomicrographs has been chosen for the Science Art show at this year’s Science Online conference in Raleigh. Here it is:
Milligan’s Trichrome stain gives this thin slice of alligator tissue the look of a stained-glass window, with scarlet strips of smooth muscle interspersed between bands of blue collagen fibers.
Assembly was remarkably fast: it took me less than 30 minutes. The kit really does just snap together – no glue, no sanding, no prep beyond peeling protective paper off each side of the plywood pieces. The peeling is necessary -- the tolerances of the laser-cut pieces are so tight that the kit’s tabs won’t go through its slots until the paper is removed – but the end result is a model without any wobble or shimmy. The trickiest part was threading the thin string through the tiny holes in the sling, and that’s more of a comment on my middle-aged eyes than anything else.
The kit comes with a pair of superballs as ammo. I used one for the inaugaral throw. Foolishly. Inside the house. I didn’t break anything, but we’re still looking for one of the balls. After that, we switched to crumpled balls of paper and were consistently shooting them 30 feet across the room. Our cat now thinks we bought the treb for her. You can order one for your very own at siegetoys.com.
Our last CSA share of the year contained a lovely surprise – three ears of popcorn, still on the cob. My kids were excited, because although our CSA also gives us a bountiful share of sweet corn in August, popcorn is much less like a vegetable. After all, most vegetables don’t explode.
Superficially, sweet corn and popcorn kernels look the same. But even if I’d taken the time to dry out some of that pile of sweet corn in my kitchen back in August, we’d only get a bunch of funny-smelling toasted kernels if we tried to pop it. Popcorn can explode because it has two things that sweet corn does not: a lot of hard starch in its center and a thick outer covering.
We can eat sweet corn kernels without breaking or grinding them first because they have a thin hull – it’s thick enough to provide a little snap when you bite through it, but not thick enough to break your teeth. You wouldn’t want to try that with popcorn. At least, my dentist doesn’t recommend it. But that tooth-cracking hull makes a dandy pressure cooker.
Put a bunch of popcorn into hot oil or air, and the starch and water inside the kernels heat up. As the temperature passes 100°C, the water starts to boil and turn to steam, but the hull keeps the steam from expanding and the pressure inside the kernel starts to climb. As superheated steam permeates starches in the kernel they soften and expand, raising the internal pressure even higher. By the time the temperature inside a kernel reachs 177°C, the liquids inside it are seething at pressures nine times higher than atmospheric pressure. If that weren’t bad enough, the heat also starts to melt and weaken the kernel wall. Soon, the kernel can’t hold back the maelstrom – its wall ruptures, releasing a tiny cloud of superheated steam and starch.
The amount of moisture in the kernel is critical: too little, and there’s not enough steam to break open the kernel. Too much, and the kernel wall melts and ruptures before the pressure climbs high enough to puff out the starch. (Those unpopped kernels at the bottom of the bowl? Probably lost too much moisture in storage.)
Once the kernel is open, the pressure of the starch cloud drops, and the rapidly expanding steam carries a film of starch outward. The type of starch inside the kernel determines how far the puff expands: hard starches stretch farther than soft ones. As the cloud expands, it cools until the starch sets into the shape of a miniature explosion – a puff that can soak up butter without collapsing or hold up a layer of hot sugar. Just the thing for a cold winter’s night.
Graph from Gökmen, 2004.
References:
Gökmen, Sabri 2004. Effects of moisture content and popping method on popping characteristics of popcorn. Journal of Food Engineering 65: 357–362
Hoseneya, R. C., K. Zeleznaka and A. Abdelrahmana 1983. Mechanism of popcorn popping. Journal of Cereal Science 1(1): 43-52.
McGee, H. 2004. On Food and Cooking, 2nd edition. Scribner: New York.
Diane A. Kelly Diane Kelly is a Senior Research Fellow at the University of Massachusetts, Amherst, where she studies the neural wiring and mechanical engineering of reproductive systems.
James L. Cambias Jim Cambias writes science fiction and designs games in the lonely wilderness of Western Massachusetts.
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