CHICAGO, March 25 Ladybugs may look pretty but they also have a dark side. In some places, the polka-dotted insects have become a nuisance by invading homes and crops, including some vineyards. To make matters worse, the bugs produce a foul-smelling liquid that, besides irritating homeowners, can be inadvertently processed along with grapes and taint the aroma and flavor of wine.

Now, chemists at Iowa State University in Ames, Iowa, say they have identified several compounds that are responsible for the ladybugs noxious odor, a finding that could lead to new strategies to detect and eliminate the offensive compounds. Their study, which could lead to better tasting wine, was presented today at the 233rd national meeting of the American Chemical Society.

A growing number of winemakers say that their wines have an abnormal aroma and flavor, known as ladybug taint, that resembles the bugs characteristic odor. Winemakers report that there are more ladybugs in vineyards and on the grapes during harvest. Experts believe that the bugs accidentally become mixed into the juice during processing and fermentation, resulting in inferior wine.

Led by Jacek Koziel, Ph.D., an agricultural engineer at the university, the Iowa researchers used a highly-sensitive multidimensional gas chromatograph and a panel of human sniffers to characterize and identify the odors emitted by a group of live ladybugs as many as 300 in all. All of the ladybugs were a single species of multicolored Asian ladybird beetle (Harmonia axyridis).

After sealing the bugs in test tubes in batches of five each, the odors they emitted were carefully analyzed by the researchers who detected 28 different odors. Of these, Koziel and his associates identified four chemicals that were most responsible for the characteristic ladybug odor.

All of the chemicals belong to a class of compounds called methoxypyrazines, which are potent odor-producing compounds also foun
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25-Mar-2007