Bad Wheat Sings

Scientists have figured out how to tell the good wheat seeds from the bad--the bad ones "sing."

Every year, more than $1.5 billion worth of U.S. wheat and other grains must be tossed or downgraded because of post-harvest damage by insect pests. Currently, it takes about 20 minutes for grain inspectors to sort through quarter-pound samples of grain by hand to spot wheat kernels that have been munched on by insects.

Thomas Pearson of the USDA's Agricultural Research Service has developed an acoustic technique for sorting out the bad seeds.

When a whole and intact wheat kernel hits a steel plate, it makes a slightly different, higher-pitched "ping" than an insect-spoiled seed. The sorter then sends the insect-damaged wheat kernels into one bin, and "acceptable" kernels into another.

Because individual kernels are small, lightweight and hard, any acoustic energy they emit is inaudible to human ears, so the sorting system is outfitted with a special microphone that can pick up ultra-sonic sounds.

Pearson's sorter can analyze the same sample in about 75 seconds, or at a rate of 40 kernels per second. And it successfully detects damaged kernels 87 percent of the time. It can even tell which kernels have tiny insect larvae hiding inside them--which is like finding a needle in a haystack for grain inspectors.

The technology is ready for use, but has not yet reached the market.

--Bjorn Carey

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Credit: Peggy Greb