Irradiation techniques help maintain food safety

For many people the term “food irradiation” conjures negative images of glowing radioactive food and food processing that is spooky and futuristic. Claims are made that food irradiation causes the formation of dangerous radiolytic chemicals and free radicals.

This method is not new, however. It has been under extensive study for more than 100 years, and its use in food processing has been regulated in the United States by the Food and Drug Administration for about 50 years. As world food demands grow and food safety issues multiply, food irradiation is likely to become a more common food safety technology.

QUESTION: What is food irradiation?

ANSWER: A food is exposed to gamma rays, electron beams or X-rays, generally to enhance food safety and preserve foods by killing microorganisms such as bacteria and parasites.

Irradiation also is used to make some fresh fruits legal for export by causing sterility in the larval forms of insects such as fruit flies. Additionally, relatively low doses of irradiation can help increase shelf life by slowing the sprouting process in foods such as potatoes, by killing molds on the surface of strawberries, or by killing pathogenic bacteria on lettuce or spinach.

Food irradiation by gamma rays requires a radio­active substance, whereas irradiation by electron beams and X-rays uses special equipment that generates these forms of energy much as medical X-ray machines do.

Q: Does food irradiation make foods radioactive?

A: No. During the irradiation process, food is exposed to an energy field, but it does not come into contact with any radioactive matter. Consequently, like baggage being X-rayed or a cancer patient being treated with radiation, irradiated foods do not become radioactive.

Q: How does food irradiation affect nutrients?

A: Common methods of food processing such as canning, drying and pasteurizing all cause the loss of some nutrients. At the approved dose levels, irradiation generally causes less nutrient loss than traditional processing, largely because the temperature of the food is raised very little.

Q: Are toxic chemicals produced in irradiated foods?

A: Toxic chemicals are present naturally in foods, and all methods of improving food safety, including irradiation, cause changes in the complex chemical makeup of foods. For example, the process of toasting a slice of bread is known to produce more free radicals than common food irradiation procedures.

The safety of consuming irradiated foods has been tested in many animal species with feeding studies lasting as long as nine generations. Interestingly, food for astronauts is irradiated at a high dose level to sterilize the food and maximize its safety in space.

Q: Does irradiation affect flavor?

A: Some irradiated foods may taste slightly different, much as pasteurized milk tastes slightly different from unpasteurized milk. The extent of flavor change is dependent on the dosage of treatment and the type of food.

Q: Can you tell if a food has been irradiated?

A: Irradiated foods are labeled with an international symbol called a radura (pictured above), along with a statement indicating the food was irradiated. Consequently, consumers who choose to can avoid purchasing irradiated foods.

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Joannie Dobbs, Ph.D., C.N.S., and Alan Titchenal, Ph.D., C.N.S., are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii-Manoa. Dobbs also works with University Health Services.