Research uses X-ray to reduce foodborne pathogens on leafy greens

11/16/2009 04:42:28 PM
Bob Luder

A researcher at Mississippi State University has developed a procedure that uses X-ray technology to greatly reduce the presence of foodborne pathogens like E. coli, salmonella, shigella and listeria on leafy green vegetables.

Barakat Mahmoud, assistant professor of food safety and microbiology at Mississippi State and a spokesman for the Institute of Food Technologies, said the procedure is a form of irradiation, only without the use of radioactive compounds like Cobalt-60 and Cesium-137 used to generate gamma radiation.

“This is just an X-ray machine, electricity converted to photons,” Mahmoud said. “I believe consumers will accept X-ray more than gamma because everyone is more familiar with X-ray.”

Mahmoud said his studies never exceeded X-ray doses of more than two kilogray (the unit of measurement for X-ray) for spinach and iceberg lettuce. The Food and Drug Administration limit for using X-ray on spinach and iceberg lettuce is four kilogray.

“We were able to reduce populations of foodborne pathogens by more than 1 million cells per gram,” Mahmoud said.

Almost as important, Mahmoud said, was that the X-ray process didn’t change the color or damage the surface of the product in any way.

“I was working with Richard Linton at Purdue University, and we were doing studies with chlorine dioxide gas and iceberg lettuce,” Mahmoud said. “It turned the color of greens to brownish or some even white. Treatment with X-ray did not affect color or texture at all.

“And, it doesn’t just kill pathogens on the surface. X-ray can kill bacteria inside produce.”

Mahmoud said his studies showed X-ray treatments extended the shelf life of produce to 30 days from a microbiological perspective. After 30 days, there was presence of things such as mold and yeast. But, it only measured about 100 cells per gram for treated produce compared with 10 million cells per gram for the control group.



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