URBANA, Ill. (AP) _ College researchers are popping a mountain of corn to glean a kernel of information - how come there are always a few unpopped duds at the bottom of your bowl.

In what must be one of the best-smelling laboratories anywhere, University of Illinois researchers periodically pop 5 to 6 pounds of research popcorn an hour for several hours, then analyze the kernels that are too pooped to pop.

The brand used is that created by Orville Redenbacher, the entrepreneur who gave this snack-for-the-masses panache when he touted his popcorn as gourmet quality. Redenbacher's parent company, Beatrice-Hunt-Wesson Foods Inc., of Fullerton, Calif., gave the school $45,000 to conduct the research.

''The volume of this industry is so large that even small improvements make a significant impact on profits,'' researcher Bruce Litchfield of the College of Agriculture said earlier this week.

Americans consume about 13 billion quarts of popped corn annually and the industry has been swelling at a rate of about 5 percent a year.

There are two key quality factors in popcorn: total pop volume and the number of kernels that do not pop.

''We are interested in finding out more about how we can breed the corn for better popability, how we can harvest it to avoid damage to the kernels, and how we can store it to maintain the right percentage of moisture,'' said Kay Carpenter, spokeswoman for Beatrice-Hunt Wesson, itself a subsidiary of Chicago-based BCI Holdings Corp.

Redenbacher's popcorn, packaged for both stovetop and microwave preparation, is the market leader. Research produced the high-quality brand, and research will lead to further improvements, said Ms. Carpenter.

''He bred his corn to pop fluffier and to have a more tender, less chewy, texture. But unpopped kernels were his real pet peeve,'' she said.

When the popcorn arrives from the Redenbacher facility in Valparaiso, Ind., it is stripped from the cob mechanically. Researchers pop it in a movie theater popper, measure the volume and dump it onto a screen, where unpopped kernels fall through for counting.

More than 800 pounds have been popped in the name of science since the project began in March. Some of the data is eaten on the spot, but much of it is given to a local elementary school, said UI food engineer Steve Eckhoff.

Kernels pop when heat turns internal moisture into steam, creating pressure that bursts the outer shell. The pressure cannot build in kernels with cracked coatings, so they either don't pop or pop only partially.

Factors that influence a kernel's popability is damage to the shell when it is stripped from the cob, and too much or too little moisture, Eckhoff said.

Researchers have identified two techniques to loosen kernels from the ears before stripping. One is preconditioning cobs by changing temperature and humidity; the other is using an enzyme to help break the bond between kernel and cob.

Corn that has been mechanically shelled has twice as many unpopped kernels as hand-shelled corn, and less total pop volume, he said.

Still, there are usually no more than 30 duds - called UPKs in the trade, for unpopped kernels - in a jar of 4,000 kernels of high-quality popcorn.

That may sound too paltry to study, but as Eckhoff said: ''A UPK doesn't mean much until you bite down on it.''