Scientists at Purdue began experiments using the gas to kill pathogens found on food long before anthrax was detected in mail sent to offices in New York and Washington, D.C., shortly after the terrorist attacks one year ago. The latest university test measured how effectively different potencies of chlorine dioxide (ClO2) gas used over various periods of time could kill Listeria monocytogenes cells on apples.

Results of the study, published in the September issue of Food Microbiology, demonstrated that the vapor was able to eradicate all of the contaminant on the fruit's skin and significantly reduce the bacteria in the stem cavity and the calyx, said Richard Linton, director of Purdue's Center for Food Safety Engineering and senior author. The calyx is the apple's bottom, directly opposite from the stem cavity.

"We see more and more cases of food-borne diseases associated with fruits and vegetables," Linton said. "Some of this is because we encourage people, especially children and the elderly, to eat more and more of these types of foods for added health benefits. Yet these are two of the groups most susceptible to bacteria on food.

"Just 10 to 100 cells of Listeria on a piece of food can cause illness, and it's possible for 1,000 to 10,000 cells to be on a piece of fruit. We need to develop ways to make food safer; traditional sanitation methods to remove pathogens are not effective enough to meet these new standards."

Although Listeria is relatively rare, it is considered the most deadly of the food-borne pathogens with a 20 percent fatality rate. The Clinton administration issued a "no tolerance" edict for Listeria in processed and ready-to-eat foods, such as hot dogs,
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Contact: Susan A. Steeves
ssteeves@purdue.edu
765-496-7481
Purdue University
12-Sep-2002