It's about time someone figured this out. Jeez.
http://story.news.yahoo.com/news?tmpl=story&cid=624&e=1&u=/ap/popcorn_s_secretINDIANAPOLIS - 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.