By James Wright, Senior Editor
Published on 22 April, 2009
Timid raw bar recruits may soon run out of excuses to hoist a halfshell. Live oysters, it appears, may not be much of a health risk after all, if a newly approved yet controversial shellfish processing technique in the United States catches on.
Irradiation, or the use of radioactive energy, is actually not new at all, having been first used on food more than 40 years ago. But while the U.S. Food and Drug Administration has long approved irradiation on foods like meat and eggs, the market remains limited partly because irradiated products must be labeled as such. The agency approved irradiation for only some produce last summer.
But for oysters, which can carry microorganisms and the stigma of potential sickness to those who consume them raw, a "Radura" logo - the international symbol indicating irradiated foods - could be the seal of approval some wary seafood consumers want to see. University of Florida researchers say a method they developed is now FDA-approved, and a Louisiana oyster supplier says irradiated oysters will be on the market in the coming weeks.
Dr. Steve Otwell, Ph.D., extension seafood specialist at the Gainesville, Fla., school's Aquatic Food Products Lab, says the gamma irradiation process his research team refined along with Food Technology Service in Mulberry, Fla., is only approved for molluscan shellfish like oysters and clams. Otwell says the FDA approved the process in December.
After several years, the researchers determined a safe radiation dosage level to rid live oysters of bacteria like Vibrio vulnificus without harming the product. Vibrio, a common bacterium found in oysters in the Gulf of Mexico and elsewhere, is harmless to the shellfish but can cause serious gastrointestinal illnesses if consumed by humans.
"The dose level won't make the product radioactive, but it is strong enough to kill the bacteria," said Otwell.
Radiation is energy that moves in particles or waves; unlike sunlight and microwaves, the process does not alter the product as long as the maximum dosage level is not exceeded, which would occur if the product is exposed for too long.
In simple terms, a radioactive source - in this case, cobalt rods under water - emits ionizing radiation in a large chamber in which the material is configured to allow penetration. For shellfish processing, a pallet of oysters in typical waxed cardboard boxes is run through a chamber to be exposed to the radiation.
Motivatit Seafoods of Houma, La., has worked with Otwell's team since the beginning of the project. The oyster supplier and processor is widely known throughout the industry as a pioneer of high-pressure processing (HPP), which also rids oysters of bacteria. However, HPP also essentially shucks the oysters, which are fastened together with a gold-colored band or seal before shipping.
Irradiated oysters are a "step between natural (unshucked) oysters and Gold Band," says Kevin Voisin, VP of marketing and new business development for Motivatit, adding that the process is time- and cost-efficient. A truckload of oysters can be treated in about 40 minutes, a job that typically takes a full day with HPP.
"Irradiation has some interesting advantages. The processing is tremendously faster if you have the right facility," said Voisin. "It's not just faster - it accepts a more diverse range of oysters, they don't have to fit into a cookie cutter."
Voisin, who adds that irradiated oysters will be market-ready in three weeks to a month, doesn't see a Radura label as an obstacle. "I see it as a benefit," he said, citing the widespread availability of irradiated ground beef. "Ten years ago, I would have seen consumer perception as an issue. Today, that's significantly changed. At the foodservice level there's almost 100 percent understanding."
Illnesses from raw oyster consumption appear to be on the rise. According to a 2007 report by the Centers for Disease Control and Prevention, the number of vibrio infections confirmed in 2006 was the highest since its Foodborne Diseases Active Surveillance Network, or FoodNet, began surveillance in 1996. According to a CDC spokesperson, an average of 45 laboratory-confirmed vibriosis cases from oyster consumption were recorded annually in Gulf Coast states between 1996 and 1998. FoodNet only records incidents of foodborne illnesses in 10 states.
Still, some environmental groups oppose the use of irradiation on food products. The process, which is also widely used to sterilize objects like disposable medical instruments like syringes, has been criticized for its potential to mask poor sanitation at other phases of the food supply chain.
Food & Water Watch (FWW) of Washington, D.C., says irradiation is expensive, ineffective, impractical and potentially dangerous. In her 2008 book, "Zapped! Irradiation and the Death of Food," FWW Executive Director Wenonah Hauter said no studies show that, over the long run, irradiated foods are safe.
But since heat pasteurization is widely considered a safe method for eliminating pathogens from other types of food, proponents argue that irradiation shouldn't be assumed as a method for masking food-safety issues.