Riding on the waves

Shopping for food can be stressful and time-consuming, as there are always the following nagging questions to be considered: How was the food item processed? What additives does it contain? Was it treated with multiple pesticides or antibiotics? Has it been altered by biotechnology? Has the food been irradiated?

So far, though, it is difficult to find irradiated foods in local grocery stores. At present, chiefly frozen ground beef patties, located in the freezer section, have been treated with radiation. Fresh beef patties, found in the meat section, are not treated. Recently, irradiated frozen chicken breasts were introduced to the Florida market.

Dan Henroid, M.S., RD., coordinator of the Food Safety Project with the Iowa State University Extension Service, concurs. "Irradiated meat has been on our grocery store shelves in Iowa for some time now. We have had irradiated beef patties in Iowa since the summer of 2000."

"People are just beginning to understand the seriousness of food-borne illness, caused by bacteria and bacterial by-products, which has recently renewed the interest in irradiating foods," asserted George Pauli, Ph.D., Director of the Division of Product Policy, U.S. Food and Drug Administration (FDA). The Centers for Disease Control and Prevention (CDC) estimates that every year 76 million people get sick, more than 300,000 are hospitalized, and 5,000 Americans die because of foodborne illness. Ultimately, the expense for this preventable disease becomes the taxpayer's burden.

"Moreover, there is additional pressure from the meat and poultry industry to promote irradiation, as recalls due to bacterial contamination are becoming very expensive," states Dan Henroid. The meat industry has had to convince the public that it is providing a microbial safe food product, particularly after the recent high-profile outbreaks of Escherichia coli and Listeria.

The goal of meat irradiation is not to extend the shelf life, since frozen food products already have a long shelf life, but to provide a safe food product. However, bacteria that cause foodborne illness are easier to destroy than spoilage bacteria. Irradiated meat products still harbor spoilage bacteria, which can multiply; therefore, irradiated food products must be stored with care.

Fruits and vegetables are not commonly irradiated. However, an irradiation facility is under construction in Hawaii, although the purpose of this operation is insect control.

"When you have an island like Hawaii that exports to a variety of countries, each country having different insect quarantine regulations, there is an advantage to irradiation, as it basically meets everyone's insect control issues," explains James Dickson, Ph.D., Chair of the Department of Microbiology, Iowa State University. As a bonus, according to Dr. Bruhn, the shelf life of the fresh produce would be approximately doubled.

Energy rays are an integral part of the universe and all living life forms on earth. Long wavelengths, such as radio waves, television broadcast waves, and light, cannot be used to cook or preserve food; however, microwaves, infrared (heat waves), ultraviolet light (sun rays), and ionizing wavelengths--known as gamma rays and x-rays--can be. When food is irradiated, a concentrated source of short ionizing energy waves is used.

Three types of energy sources can produce these rays. Electricity can generate electron beams and x-rays, and radioactive materials (such as cobalt-60 or, less frequently, cesium-137) are used to produce gamma rays. Cobalt-60 is readily available and degrades to nonradioactive nickel. Cesium-137, which decays to nonradioactive barium, is found in spent fuel elements from nuclear reactors. It is not used much any more because it emits inconsistent doses of energy, making it difficult to control. Dr. Pauli acknowledged that x-rays are not cost-efficient because much energy is required to produce the x-rays. As a result, most ionizing energy waves are derived from a process using cobalt-60.

Is the food likely to become radioactive when it is penetrated with radiation waves? Because ionizing energy cannot penetrate the nucleus and interacts only with electrons, the food does not become radioactive. When the electrons are knocked out of orbit, however, free unstable radicals-chemical components uncomfortably lacking an electron--are formed.

Are these unstable radicals harmful? Probably not, maintains the food industry, since cooked foods also undergo similar changes when they are irradiated with infrared heat waves. The drawback to irradiating foods with heat waves is that heat radiation tends to change organoleptic properties. Ionizing radiation wavelengths barely affect the appearance and taste of the food, and very few nutrients are lost.

Despite the seeming newness of ionizing radiation technology as a food preservation process, it has been in existence since 1895, with Wilhelm Roentgen's discovery of x-rays in 1894 and Henri Becquerel's discovery of radioactivity in 1895. Ionizing energy was at first a scientific curiosity. The newly discovered form of energy called ionizing rays, consisting of x-rays, gamma rays, and radioactive isotopes, was a wonderful novelty.

"It really opened up a whole new page of nature. It was remarkable that there were visionaries who could see that this form of energy could have useful applications to everyday kinds of concerns. These visionaries blazed the pathways for the rest of us," marvels Joseph Borsa, Ph.D., Food Irradiation Specialist with MDS Nordion, a large company that operates several irradiation facilities in Canada and the United States.

When ionizing rays were first discovered, widespread application of radiation was not possible; the only way to make ionizing radiation was to use radium, and radium was scarce and expensive. The technical equipment to expose large quantities of food items to ionizing rays was nonexistent. In addition, early on, when scientists exposed food to ionizing rays, the resultant food products tasted, smelled, and looked bad.

After World War II, research on irradiation using ionizing rays as a means of food preservation began in earnest. According to Dr. Borsa, "Scientists now had sources of ionizing energy in labs around the world. The questions that are being raised today about the safety of this process were the same questions scientists puzzled over in the 1950's. Research intensified as many investigators were looking for answers."

The U.S. Atomic Energy Commission experimented with food preservation using spent fuel rods from nuclear reactors (cesium-137). The U.S. Army concentrated on meat sterilization, searching for an alternate method of preserving meat to be transported and consumed by troops in the field. These experiments were unsuccessful, however, because only cesium-137 was available and it produced unpredictable radiation dosages.

In the late 1950's, the Atomic Energy Commission deliberately manufactured cobalt-60 to preserve food. Cobalt-60 was able to deliver constant rates of predictable radiation. The commercial application of irradiation food processing was gradually introduced around the world in the late 1950's and early 1960's.

After the initial introduction to the process in the 1960's, the FDA shut down all approvals for food irradiation until the mid-1980's. By this time, results from years of research and analysis had been distilled. Food irradiation was determined to be a safe process. At the same time, the Joint Expert Committee on Food Irradiation (JECFI), which represents most countries, concluded that all foods irradiated with 10 kilogray (kGy) or less, the maximum level for food pasteurization, was not toxic and would not affect the nutrients. Concurrently, the Environmental Protection Agency (EPA) banned ethylene dibromide, a postharvest fumigant used to control vegetable and fruit infestation. Therefore, companies were seeking another way to control infestation. Irradiation resurfaced.

The three sources of ionizing energy (gamma rays, x-rays, and electron beams) have now become more readily available and cheaper to manufacture. The number of companies that offer irradiation services is growing. In 1997, the JEFCI concluded that foods could safely be irradiated with any dose of radiation as long the food product maintained high-quality organoleptic properties. Why, then, are more irradiated foods not found in grocery stores?

"Now that radiation technologies have been perfected, irradiation is competing against more preservation options than in the early twentieth century when food preservation was just beginning to become a reality," notes Dr. Pauli. Unlike a hundred years ago, a variety of food preservation methods are now available--each serving a different purpose.

"It now takes longer to promote and to prove the benefits of one technology over another, Nevertheless, the times are slowly changing. Irradiated ground beef patties are now selling in 200 stores around the country," he says.

Dan Henroid adds, "Irradiation is also an important device to extend the shelf life of foods so we can be able to better distribute food commodities to those who do not have access to foods or for those countries that have trouble getting food to the people."

According to the Food and Agricultural Organization, we lose one quarter to one half of the world's food supply to spoilage, insect infestation, and bacterial and fungal attack.

The National Aeronautics and Space Administration (NASA) has used irradiated foods in the space program since 1972. Astronauts need a diverse menu consisting of foods with an extended shelf life and devoid of pathogenic organisms. High doses of irradiation are used to sterilize NASA's foods, which destroy both bacteria and spoilage enzymes. However, this sterilized food is not available to the average consumer.

The Republic of South Africa is the only country in which precooked, shelf-stable meat products, irradiated at 45 kilogray (sterilization doses), are allowed for retail sale. "South Africa is a leader in producing shelf stable irradiated foods," explains Dr. Bruhn. This operation was initiated in order to safely produce quantities of military foods. When the military operations were reduced, South Africa sold the sterilized food products to consumers who desire menu variety while on extended hiking trips or ocean voyages.

The latest agricultural crisis involves disturbing contemporary plagues such as hoof-and-mouth disease, caused by a virus, and mad cow disease, possibly the result of prions, which may be affecting our food supply right now. Can we stop the spread of these diseases using irradiation technology?

"No," declares Dr. Pauli. "Irradiation with ionizing beams only annihilates growing and multiplying cells such as bacteria. Low doses of ionizing radiation interfere with cell division, preventing the multiplication of bacteria, parasites, and insects. It cannot destroy smaller particles such as viruses or proteins (prions)."

"Irradiation is a tool that can solve certain very real problems that affect the consumers," elaborates Dr. Borsa. "Any tradesman needs a variety of tools in his kit, and so radiation in terms of the food safety tool kit is just one tool--but an excellent tool. You need some kind of intervention technology to stop the microbial hazards from reaching the consumer, and irradiation is superb for controlling that hazard. Can it solve all the problems of the world? No, of course not. This is not a magic wand that can solve all problems related to agriculture."

"It is the position of the American Dietetic Association that food irradiation enhances the safety and quality of the food supply and helps protect consumers from foodborne illness. The ADA encourages the government, food manufacturers, food commodity groups and qualified food and nutrition professionals to work together to educate consumers about this additional food safety tool and to make this choice available in the marketplace."

Journal of The American Dietetic Association (February 2000, page 2)

Debra Johnson, M.S., R.D., L.D.N., has worked with federal food programs and population studies for over 15 years. She has written articles on a variety of nutrition topics and data studies and maintains a special interest in maternal and child health.

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