view current print edition




Experts say irradiation is no magic bullet

by Joan Murphy | January 21, 2009
Irradiation may be effective in ridding fresh produce of pathogens, but it may not be so easy to bring irradiated fresh produce to the marketplace.

It is no secret that foodborne outbreaks are causing the industry to take a closer look at the technology, especially after the U.S. Food & Drug Administration gave its approval last August to use irradiation for killing pathogens on Iceberg lettuce and spinach. But is the technology a good fit for various commodities? And how effective is it?

The University of California-Davis' Postharvest Technology Research & Information Center explored the issue during a Jan. 12 webinar titled Produce Irradiation: Food Safety Solution? It was moderated by Jim Gorny, executive director of the center.

Harlan Clemmons, president and chief operating officer of Sadex Corp., a Texas-based company that operates electron beam technology, said that it would take about three to four weeks to test the right dose for a new product and its packaging. And it takes about nine to 12 months to site a new irradiation facility, he said.

Despite the cost, which he predicted would add 10-25 cents per pound, irradiation alone cannot be used to reduce contamination, experts said. Irradiation is a powerful tool if used correctly, but it is not a magic bullet, said Robert Buchanan, retired FDA chief scientist and now director of the University of Maryland's Center for Food Safety & Security Systems. More work is needed to determine the effectiveness in different produce items and among different varieties.

Irradiation may not be very effective at killing pathogens if they are internalized in fresh salad greens, he said. The technology is touted as the only solution for destroying internalized pathogens without cooking.

But recent studies with four lettuce varieties and E. coli O157:H7 showed that internalized cells are more resistant to radiation than those on the surface of the produce, he said. While radiation may be better than most technologies in penetrating fresh produce, the industry may still need to minimize internalization, said Dr. Buchanan.

The University of California's Adel Kadar of the Department of Plant Sciences said that irradiation is a supplemental technology, not a substitute for good handling.

Dr. Kadar, who spoke on the effects of irradiation on produce quality, said that it was important to identify the proper commodity-specific dose so that the quality of fresh produce is not jeopardized. He said that the symptoms of too high a dose, such as yellow or brown leaves, does not occur until days after the treatment and is dependent on the temperature and humidity of post-treatment handling.

It is further necessary to carefully maintain the cold custody chain with irradiated products to prevent stress and maintain the product's quality, Dr. Kadar said. He also suggested that companies use a technology that minimizes the dose range within a pallet and within a box of produce to reduce irradiation damage.

The question of whether consumers will buy irradiated fresh produce was addressed by Christine Bruhn of the University of California's Center for Consumer Research. She said that consumers are willing to buy irradiated foods if they are educated on the benefits. Studies show acceptance of irradiation increases when people hear who endorses it, such as health organizations, and when consumers see the product.

But she said that there have been no studies gauging consumer interest in buying irradiated produce to reduce the risk of foodborne illness.