Eat your way to the bottom of almost any bag of popcorn and there they are: the rock-hard, jaw-rattling unpopped kernels known as old maids.
The nuisance kernels have kept many a dentist busy, but their days could be numbered: Scientists say they now know why some popcorn kernels resist popping into puffy white globes.
It’s long been known that popcorn kernels must have a precise moisture level in their starchy center to explode. But Purdue University researchers found the key to a kernel’s explosive success lies in the composition of its hull.
Unpopped kernels, it turns out, have leaky hulls that prevent the moisture pressure buildup needed for them to pop and lack the optimal hull structure that allows most kernels to explode.
“They’re sort of like little pressure vessels that explode when the pressure reaches a certain point,” said Bruce Hamaker, a Purdue professor of food chemistry. “But if too much moisture escapes, it loses its ability to pop and just sits there.”
The findings may help popcorn breeders select the best varieties or create new ones with superior hulls that yield few, if any, unpopped kernels.
Wendy Boersema Rappel, a spokeswoman for the Chicago-based Popcorn Board, said popcorn processors are always looking for ways to improve their product, including reducing the number of old maids.
“It’s one of life’s annoyances–it’s not rocking anyone’s world, but our members always like to improve their product,” Rappel said.
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Compiled from news services and edited by Curt Wagner (cwwagner@tribune.com) and Drew Sottardi (dsottardi@tribune.com)
