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Here are two short documents on food irradiation.
Other good resources for food irradiation information:
Food Fact Safety Sheet
By Charlotte P. Brennand, PhD, Extension Food Safety Specialist
1. Why is food irradiated?
Food is irradiated to provide the same benefits as when it is processed by heat, refrigeration, freezing or treated with chemicals to destroy insects, fungi or bacterial that cause food to spoil or cause human disease and to make it possible to keep food longer and in better condition in warehouses and homes.
Because irradiation destroys disease-causing bacteria and reduces the incidence of food borne illness, hospitals sometimes use irradiation to sterilize food for immuno-compromised patients.
2. Are irradiated foods still nutritious?
Yes. Irradiated foods are wholesome and nutritious. All known methods of food processing and even storing food at room temperature for a few hours after harvesting can lower the content of some nutrients, such as vitamins. At low doses of radiation, nutrient losses are either not measurable or, if they can be measured, are not significant. At the higher doses used to extend shelf-life or control harmful bacteria, nutritional losses are less than or about the same as cooking and freezing.
3. Does irradiation make food radioactive?
No. Radioactivity in foods can occur by two routes: contamination of foods with radioactive substances or by penetration of energy into the nuclei of the atoms that make up the food.
The irradiation process involves passing food through an irradiation field; however, the food itself never contacts a radioactive substance. Also, the ionizing radiation used by irradiators is not strong enough to disintegrate the nucleus of even one atom of a food molecule.
4. Does eating irradiated food present long-term health risks?
No. Federal government and other scientists reviewed several hundred studies on the effects of food irradiation before reaching conclusions about the general safety of the treatment. In order to make recommendations specifically about poultry irradiation, U.S. Food and Drug Administration scientists reviewed findings form additional relevant studies.
Independent scientific committees in Denmark, Sweden, United Kingdom and Canada also have reaffirmed the safety of food irradiation. In addition, food irradiation has received official international endorsement from the World Health Organizations and the International Atomic Energy Agency.
5. Does irradiation destroy all bacteria, resulting in a sterile produce?
Irradiation, at the levels normally used in food processing, destroys most, but not necessarily every single microorganism present; it does not sterilize the food.
As with any food, consumers must take appropriate precautions, such as refrigeration and proper handling and cooking, to make sure that potentially harmful organisms do not present a problem.
After treatment, the surviving disease-causing and food spoilage organisms may start to multiply again if the food is not properly handled. The disease-causing organisms in irradiated food are just as dangerous, but not more so, as the same organisms in non-irradiated food.
One concern has been that irradiation does not kill the bacteria that causes botulism. However, studies also have shown that in both irradiated and non-irradiated food, spoilage organisms will grow and alert consumers to spoilage before botulism-causing bacteria can produce toxin.
6. Does irradiation cause chemical changes in food, producing substances not known to be present in non-irradiated food?
Yes, irradiation does produce chemical changes in foods. These substances, called "radio-lytic products", may sound mysterious, but they are not. They have been scrutinized by scientists in making safety assessments of irradiated foods. Any kind of treatment causes chemical changes in food. For instance, heat treatment, or cooking, produces chemicals that could be called "thermolytic products." Scientists find the changes in food created by irradiation minor to those created by cooking. The products created by cooking are so significant that consumers can smell and taste them, whereas only a chemist with extremely sensitive lab equipment may be able to detect radiolytic products.
7. Will my risks of radiation exposure increase significantly if I live next to an irradiator?
No. The use and transportation of radioactive materials, including the facilities in which they are used and the equipment in those facilities, is closely monitored by the Nuclear Regulatory Commission, state agencies and the Department of Transportation.
The radioactive material itself is sealed within two layers of metal that prevent corrosion and oxidation. When shipped, it is placed within brick layers of lead that prevent gamma rays from escaping.
Facilities must include many safety features to prevent both environmental and worker exposure. For example, when radioactive cobalt is in the storage position in an irradiator, it is under water and otherwise shielded. The irradiator is operated by remote control, and many other protections are required to prevent workers form entering the irradiation enclosure.
8. For what other purposes is irradiation technology now used in the United States?
In addition to cancer treatment, irradiation is used for many purposes, including: performing security checks on hand luggage at airports, making tires more durable, sterilizing manure for gardens, making non-stick cookware coatings, purifying wool, sterilizing medical products like surgical gloves, and destroying bacteria in cosmetics.
9. Are irradiated foods on the market now?
Until recently, only irradiated dried spices and enzymes were marketed in the United States. In January 1992, irradiated Florida strawberries were sold at a North Miami supermarket. Sales of irradiated products are ongoing in several grocery stores. Poultry irradiation began commercially in 1993.
Irradiation of food has been approved in 37 countries for more than 40 products. The largest marketers of irradiated food are Belgium and France (each country irradiates about 10,000 tons of food per year), and the Netherlands (which irradiates bout 20,000 tons per year).
10. How can irradiated foods be identified in the market?
Irradiated food cannot be recognized by sight, smell, taste, or feel. Irradiated foods will be labeled with a logo, along with the words "Treated with Radiation", or "Treated by Irradiation."
(This publication includes information modified from the Food Inspection Service, USDA, information on irradiation.) Utah State University is an Equal Opportunity/Affirmative Action Institution. Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Robert L. Gilliland, Vice President and Director, Cooperative Extension Service, Utah State University, Logan, Utah. (EP/3-95/DF)
North Central Regional Extension Publication 437. Sponsored by the Extension Services of Iowa, Nebraska, South Dakota and Wisconsin in cooperation with ES-USDA. For copies of this publication, contact an Extension unit in one of the sponsoring states. Reprinted March 1993. Programs and activities of the Cooperative Extension Service are available to all without regard to race, color, sex, age, religion, national origin, or handicap.
Radiation is broadly defined as energy moving through space in invisible waves. Radiant energy has differing wavelengths and degrees of power. Light, infrared heat, and microwaves are forms of radiant energy. So are the waves that bring radio and television broadcasts into our homes. Broiling and toasting use low-level radiant energy to cook food.
The radiation of interest in food preservation is ionizing radiation, also known as irradia-tion. These shorter wavelengths are capable of damaging microorganisms such as those that contaminate food or cause food spoilage and deterioration.
That capability, plus the fact that much of our food supply is lost due to spoilage and insects each year is why scientists have been experimenting with irradiation as a method of food preservation since 1950. They have found irradiation to be a controlled and very predictable process.
Irradiation can be compared to pasteurization
As in the heat pasteurization of milk, the irradiation process greatly reduces but does not eliminate all bacteria. Irradiated poultry, for example, still requires refrigeration, but would be safe longer than untreated poultry. Strawberries that have been irradiated will last two to three weeks in the refrigerator compared to only a few days for untreated berries.
Two things are needed for the irradiation process
Specially constructed containers or compartments are used to confine the beams so personnel won't be exposed. Radioisotopes are used in medical research and therapy in many hospitals and universities. They require careful handling, tracking, and disposal. Machines that produce high-energy beams offer greater flexibility. For example, they can be turned on and off unlike the constant emission of gamma rays from radioisotopes.
What happens when food is irradiated?
Irradiation is known as a cold process. It does not significantly increase the temperature or change the physical or sensory characteristics of most foods. An irradiated apple, for example, will still be crisp and juicy. Fresh or frozen meat can be irradiated without cooking it. During irradiation, the energy waves affect unwanted organisms but are not retained in the food. Similarly, food cooked in a microwave oven, or teeth and bones that have been X-rayed do not retain those energy waves.
What foods are irradiated?
Irradiation has been approved for many uses in about 36 countries, but only a few applications are presently used because of consumer concern and because the facilities are expensive to build. In the United States, the Food and Drug Administration (FDA) has approved irradiation for eliminating insects from wheat, potatoes, flour, spices, tea, fruits, and vegetables. Irradiation also can be used to control sprouting and ripening. Approval was given in 1985 to use irradiation on pork to control trichinosis. Using irradiation to control Salmonella and other harmful bacteria in chicken, turkey, and other fresh and frozen uncooked poultry was approved in May 1990.
What concerns are raised by opponents of food irradiation?
The term irradiation often evokes fears of nuclear radioactivity and cancer among consumers. The process seems frightening because it is powerful and invisible. Consequently, questions and concerns exist, particularly about the safety or wholesomeness of irradiated food. Here are some commonly asked questions.
Are irradiated foods radioactive?
No, but the similarity between the two words is confusing. It is physically impossible for irradiated food to be radioactive just as your teeth are not radio-active after you have had a dental X-ray. Irradiation is radiant energy. It disappears when the energy source is removed.
Are toxic radiation products produced?
Over the past 30 years, researchers in several countries have evaluated irradiated foods for chemical products (radiolytic products) which may have formed. The toxicity of those products has been studied also.
What are some potential applications for food irradiation? Because the irradiation process works with both large and small quantities, it has a wide range of potential uses. For example, a single serving of poultry can be irradiated for use on a space flight. Or, a large quantity of potatoes can be treated to reduce sprouting during warehouse storage.
However, irradiation cannot be used with all foods. It causes undesirable flavor changes in dairy products, for example, and it causes tissue softening in some fruits, such as peaches and nectarines.
Irradiation is most useful in four areas.
Irradiation can be used to destroy or inactivate organ-isms that cause spoilage and decomposition, thereby extending the shelf life of foods. It is an energy-efficient food preservation method that has several advantages over traditional canning. The resulting products are closer to the fresh state in texture, flavor, and color. Using irradiation to preserve foods requires no additional liquid, nor does it cause the loss of natural juices. Both large and small containers can be used and food can be irradiated after being packaged or frozen.
Foods that are sterilized by irradiation can be stored for years without refrigeration just like canned (heat sterilized) foods. With irradiation it will be possible to develop new shelf-stable products. Sterilized food is useful in hospitals for patients with severely impaired immune systems, such as some patients with cancer or AIDS. These foods can be used by the military and for space flights.
Control sprouting, ripening, and insect damage
In this role, irradiation offers an alternative to chemi-cals for use with potatoes, tropical and citrus fruits, grains, spices, and seasonings. However, since no residue is left in the food, irradiation does not protect against reinfestation like insect sprays and fumigants do.
Control foodborne illness
Irradiation can be used to effectively eliminate those pathogens that cause foodborne illness, such as Salmonella.
All methods used to process and preserve foods have benefits and limitations. Some possible applications for irradiation with certain foods are shown in Table 1.
Opponents of irradiation worry that these radiolytic products are hazardous. Biochemical and biomedical tests have not been able to identify any health prob-lems or ill effects associated with tested radiolytic compounds.
How is food irradiation regulated?
The Food and Drug Administration (FDA) regulates all aspects of irradiation: what products it can be used on, what dose can be used, and how those products are labeled. The U.S. Department of Agriculture (USDA) is responsible for the inspection and monitoring of irradiated meat and poultry products and for the enforcement of FDA regulations concerning those products. Since 1986, all irradiated products must carry the international symbol called a radura, which resembles a stylized flower.
FDA requires that both the logo and statement appear on packaged foods, bulk containers of unpackaged foods, on placards at the point of purchase (for fresh produce), and on invoices for irradiated ingredients and products sold to food processors.
Processors may add information explaining why irradiation is used; for example, treated with irradiation to inhibit spoilage or treated with irradiation instead of chemicals to control insect infestation.
Accurate plant records are essential to regulation because there is no way to verify or detect if a product has been irradiated, or how much radiation it has received. Is nutritional quality reduced? Scientists believe that irradiation produces no greater nutrient loss than what occurs in other processing methods, such as canning. For specific comparisons, see Tables 2 and 3. Table 2. Thiamin retention comparison MeatPercent in irradiated samplePercent in canned sample Beef 21 44 Chicken 22 66 Pork 12 57
Reference: Journal of Food Science 46:8, 1981.
Reference: Journal of Food Processing and Preservation 2:229, 1978
Where can I get more information? For answers to questions about food irradiation or other food safety concerns, contact your local county extension office.
Blumenthal, D. "Food Irradiation: Toxic to Bacteria, Safe for Humans." FDA Consumer. November 1990.
"Food Irradiation: A Most Versatile 20th Century Technology for Tomorrow." A Symposia presented at the 1989 Annual Meeting of the Institute of Food Technologists, Chicago, IL. Food Technology. July 1989.
"Ionizing Energy in Food Processing and Pest Control: Wholesomeness of Food Treated With Ionizing Energy." Council for Agricultural Science and Tech-nology. Report No. 109. July 1986.
"Ionizing Energy in Food Processing and Pest Control: Applications." Council for Agricultural Science and Technology. Report No. 115. June 1989.
Jay, James. Modern Food Microbiology. Van Nostrand Reinhold Company, New York, NY. 1986.
"Radiation Preservation of Foods." A Scientific Status Summary by the Institute of Food Technologists' Expert Panel of Food Safety and Nutrition. February 1983.
Reviewed by Dennis Olson, Ph.D., Director, Utilization Center for Agricultural Products, Iowa State University. Written by Patricia Redlinger, Iowa State University extension food science specialist, and Diane Nelson, Iowa State University extension communication specialist.