Can Irradiating Food Zap Salmonella Outbreaks?

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X-rays, ozone, and high pressure are among new options for stopping outbreaks salmonella

By Nancy Shute

Posted February 26, 2009

The salmonella outbreak involving peanuts products just keeps on going, and federal officials say it could continue another two years. With at least 666 people in 45 states sick and nine dead, that's not good news. Could irradiating peanuts with X-rays stop the killer bug?

X-raying food is just one notion that's being tested to prevent foodborne disease outbreaks. The new technologies—and some controversial old ones, like food irradiation with gamma rays, a high-energy form of electromagnetic radiation—are gaining increased interest as a result of the salmonella outbreak, which has been traced to plants operated by Peanut Corp. of America in Blakely, Ga., and Plainview, Texas.

Here are some common foods that have been treated to kill microbes:

1. Irradiated produce. Last August, the Food and Drug Administration said producers can irradiate iceberg lettuce and spinach, which have been the source of serious outbreaks in the past 10 years. Gamma rays kill bacteria by destroying their DNA, but they are less effective on viruses. The produce-zappers are not in wide use, and irradiated produce must be labeled. The FDA approved gamma radiation for treating raw and processed meats in 1997.

2. X-rayed nuts and meat. When it comes to disinfecting ground beef and poultry, X-rays are more potent than gamma rays, so less radiation needs to be used. X-rays also may work better on nuts, meat, and other high-fat foods that tend to become rancid when irradiated with gamma rays. Researchers at Michigan State University are testing X-rays on walnuts and almonds as well as ground beef. They've also launched a technology start-up, Rayfresh Foods of Ann Arbor, that is building an X-ray machine to treat ground beef for Omaha Steaks. The machine uses higher doses of X-rays than does a medical X-ray machine.

3. Pressure-treated shellfish. High-pressure processing at up to 87,000 pounds per square inch is widely used to shell lobsters and crabs. As a bonus, it kills pathogens like hepatitis A and coliform bacteria. High pressure is used to sterilize guacamole, salsa, and oysters, too. But don't try this on strawberries, unless you're looking to make strawberry puree.

4. Ozone for leafy greens and meat. Ozone, a naturally occurring form of oxygen, was approved by the FDA in 2001 for use in sanitizing food contact surfaces and food. Ozone treatment is also widely used for disinfecting municipal water. Companies and university researchers are experimenting with using ozonated water or gas to disinfect fresh fruits and vegetables and to knock back bugs like listeria in meat processing plants. (Poultry processors currently use a chlorine rinse on raw poultry, which is one reason why European Union countries ban U.S. chicken imports.)

5. Bacteria-killing viruses in packaged meats. The FDA approved use of bacteriophages, naturally occurring virus-killers, in packaged meats in 2006. Phages are used in at least one brand of packaged smoked salmon. But companies have to say on labels that the bugs are inside, which gives some consumers and retailers cold feet.

"We think food irradiation in general is a tool that, like other treatments that reduce pathogens, has great potential for food safety," says Robert Tauxe, deputy director of the Center for Disease Control and Prevention's Division of Foodborne, Bacterial and Mycotic Diseases. "I think food would be safer if we made a lot more use of it."

Although the World Health Organization also has approved the irradiation of food, it continues to have a bad rap among some food safety advocates, who say it will affect quality and taste. Irradiation is not permitted on organic foods in the United States. (Here's a more in-depth look at the food irradiation controversy.)

But even radiation is no magic bullet. "When salmonella gets in a dry environment, it is significantly more resistant to heat," says Brad Marks, a professor in Michigan State's Department of Biosystems and Agricultural Engineering, who is about to test X-rays as a method to decontaminate almonds and walnuts. "There's a salmonella that has gotten on almonds and caused two outbreaks."



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