Irradiation: Turning on the high beams

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Farm News staff writer

AMES — The salmonella outbreak linked to peppers that sickened more than 1,200 people in 42 states this summer has brought food safety to the forefront once again, and researchers at Iowa State University, who have long promoted food irradiation, say this is too beneficial a technology not be used.

“I believe the adoption of food irradiation will come, especially with the support of public health officials,” said Dr. Dennis Olson, a professor of animal science, who directs ISU’s Linear Accelerator Facility, which was installed in 1993. The LAF is one of only two commercial-sized irradiation facilities for food research and demonstration on a U.S. university campus. “Unfortunately, the technology only advances when there’s a catastrophe,” Olson said.

Consider the deadly 2006 E. coli outbreak linked to spinach and lettuce, Olson pointed out, which sickened nearly 200 people in 26 states and led to 109 hospitalizations and three deaths. In response, the U.S. Food and Drug Administration recently allowed irradiation to be used on fresh spinach and iceberg lettuce to kill illness-causing bacteria.

Had the FDA rule been in place before August of 2008, Olson is convinced that irradiation, which is sometimes described as cold pasteurization, could have prevented some of the 2006 illnesses and deaths.

“If we treat all of the lettuce and spinach, there’s going to be a very rare instance of exposure to illness-causing microorganisms,” said Olson, who first became interested in irradiation in the early 1980s. “What’s sad is that the FDA, after a nearly nine-year review, selected only two products involved with the massive illnesses in 2006.”

The FDA is still considering what other types of produce might be safely irradiated — for example, tomatoes, peppers, and leafy vegetables such as romaine lettuce.

Learning from history

At ISU’s Linear Accelerator Facility, the irradiation process uses electricity to protect food safety by blasting electrons through the food. Since the largest molecules have the highest probability of being hit, the DNA contained in any harmful microorganisms that might be present is damaged during the irradiation process. While this DNA damage prevents the unwanted microbes from reproducing, irradiation does not cook the food like heat does and ensures a high quality final product.

A number of food companies are already using irradiation to promote food safety. Many of the spices that are incorporated into processed foods are irradiated, said Olson, who added that Omaha Steaks’ ground beef is irradiated, as is all the ground beef sold through Schwan’s home delivery. “We wouldn’t have the irradiation of ground beef today, however, without the deadly 1990s E. coli outbreak at Jack in the Box restaurants,” Olson said.

What’s significant about the new FDA rule regarding irradiation is that this is the first time the federal government has allowed produce to be irradiated at levels sufficient to kill E. coli, salmonella and listeria. The FDA has approved the use of irradiation to eliminate insects from wheat, potatoes, flour, spices, tea, fruits and vegetables since 1985, but it couldn’t be used to treat vegetative pathogens until now.

Olson said the slow adoption of irradiation parallels the adoption of another landmark food safety technology — pasteurization. In the early 20th century, pasteurization took about 30 years to gain widespread acceptance.

“The push for pasteurization didn’t come from dairy farmers, the public or equipment manufacturers — it came from public health officials,” Olson said. “For irradiation to gain widespread acceptance, it will need more of a push from public health professionals.”

More consumers accept food irradiation

Both Olson and his colleague Dr. Sam Beattie, an ISU Extension food safety specialist, noted that American consumers today are more willing to buy irradiated food than they may have been in the past.

The concern that irradiating vegetables might leave them limp or cause them to taste differently is no longer an issue.

“There’s been a lot of research done on that, and basically, products that have been treated with irradiation are as good or better after 14 days (typical travel time) than those that haven’t,” Olson said. Researchers now know that to kill E. coli on this type of product, irradiator operators can turn down the power of the beam, so the lettuce and spinach remain just as crisp and wholesome as if you grew it yourself, Beattie said.

“The American consumer has shown willingness to purchase irradiated products such as strawberries and meat,” Beattie added. “Once consumers understand the food safety implications, their unfounded worries about the safety of the cold pasteurization process are eliminated, even though there are a lot of naysayers and anti-irradiation people giving inaccurate information.”

The ISU professors are quick to point out that irradiation is not a magic bullet that will solve every instance of illness-causing bacteria on produce. Good agricultural practices, such as control of irrigation water and washing water, restriction of animals in produce fields, and personal hygiene of workers all affect the safety of fruits and vegetables.

Further, safe food handling practices at home and in food service establishments also are important to ensure food safety.

Looking ahead

While consumers have not reacted negatively to the label on irradiated beef, Olson said the only negative reaction is to price. “Irradiated food does cost more. If a large volume of ground beef were irradiated, however, you’d be close to full capacity at the irradiation facility, and the process could cost as little as 3 cents per pound.”

Currently, there are three primary U.S. locations for food irradiation, including the Sadex Corporation in Sioux City, Texas A&M University and Food Technology Services in Florida. Sadex, for example, can irradiate approximately 40,000 pounds of ground beef per hour.

“I suspect it will take awhile for the supply chain to get into place because of the limited number of irradiation facilities in place in the United States,” Beattie said. “These facilities are relatively expensive to build, so you have to make sure you have adequate product flow and a market for that product.”

Still, the recent FDA decision is a big step in the right direction, Olson said. “The real importance of this rule is that produce companies wouldn’t even look at irradiation technology unless the government approved it. The new FDA rule makes them more inclined to take a fresh look at it.”


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