by James Andrews | Oct 31, 2011

Since the U.S. Food and Drug Administration (FDA) began clearing irradiated foods for sale in 1963, few such foods have attained much prevalence within grocery store aisles. In fact, most markets still do not carry irradiated meats like beef, pork and poultry, despite those products becoming cleared for sale in the 1980s and 90s.

Several hurdles -- from shipping logistics to anti-radiation stigmas -- stand between food irradiation and greater public acceptance. As reported in Food Safety News in late September, sale of irradiated beef, for example, accounts for less than one-tenth of one percent of the U.S. beef market.

Food irradiation is a process designed to kill microorganisms and insects in food through exposure to electron, gamma or X-ray radiation at the end of the production chain. With the application of correct radiation doses, the process does not alter the taste of food. Along with eliminating potentially harmful pathogens, food processors can use irradiation at lower doses to increase shelf life, a development that has opened up new avenues for imports.

The list of foods permitted for irradiation by the FDA for microbial control consists mainly of iceberg lettuce, spinach, pork, poultry, beef, molluscan shellfish, fresh shell eggs and dehydrated spices. Of those, only irradiated spices see a wide availability in U.S. grocery stores, and spices are the only food permitted for irradiation by the European Union.

In 2002, the U.S. Department of Agriculture (USDA) cleared all fresh fruits and vegetables for irradiation for the purpose of controlling insects and prolonging shelf life. Today, produce imported to the continental U.S. -- such as papayas from Hawaii and mangoes from India -- may be irradiated to preserve freshness and mitigate the spread of pests.

Varying dosages of radiation determine the difference between simply preserving fruit and eliminating the microorganisms within. The FDA and USDA restrict all foods to a maximum dosage of radiation measured in kilogray (kGy), a unit of measurement denoting radiation absorption equal to one joule of energy in one-thousand kilograms of food.

For controlling pests and shelf life, fresh fruits and vegetables are limited to a 1.0 kGy dose of radiation. Iceberg lettuce and spinach, the only produce items permitted for microbial elimination, can receive up to a 4.0 kGy dose.

Refrigerated raw meat may receive up to a 4.5 kGy dose, while the meat sent up with NASA astronauts is irradiated to 44.0 kGy maximum to preserve it for extended periods of time. Spices, with a 30.0 kGy maximum, are the most heavily irradiated products available on the market.

While irradiated foods are still largely seen as niche grocery products, Michael Osterholm, Ph.D., director of the Center for Infectious Disease Research and Policy (CIDRAP), predicts that irradiation will eventually become a widely used and accepted food safety measure as public awareness of foodborne illness outbreaks continues to rise. He also said that the federal government has a responsibility to support irradiation in an attempt to reduce the estimated 48 million cases of foodborne illness in the U.S. each year.

"The Centers for Disease Control does not have irradiation on their priority list, which is really unfortunate, because it should be one of their top priorities," Osterholm said. "We need to put more pressure on the industry, because you're not going to get those harmful agents out of meat products without a final kill step that really makes a difference."

Osterholm contests food irradiation detractors' use of the "Band-aid" argument which suggests food processors may view irradiation as a fail-safe against any oversights earlier in the production chain, possibly leading to relaxed precautions. To illustrate the difficulty of avoiding microscopic contamination in a slaughterhouse setting, he uses the example of hospital surgery infection rates.

"If surgeons using sterile surgery equipment can't get lower than a 2 percent infection rate with hospital patients, how are we going to do better at slaughtering animals? It's not a function of resources; it's just not possible," he said. "It's the same with raw milk: You will not produce a safe milk short of pasteurization. You need a kill step."

Many irradiation proponents see wary public perception as the greatest obstacle for the technology to overcome. But Osterholm and others believe that as more people learn about its benefits, more will come to support irradiation and perhaps even seek out irradiated foods specifically.

By law, all foods treated with irradiation must display the radura logo on their packaging. In cases where a specific ingredient has been irradiated, the ingredients list must indicate that.

According to FDA spokesperson Sebastian Cianci, several online resources may not supply the current, correct list of foods cleared for irradiation by the FDA.