Food Irradiation

You hear a lot about Food Irradiation these days. What is it?
Food irradiation is the process of exposing food to ionizing radiation. Typical radiation sources are cobalt-60, cesium-137, x-ray machines, or electron accelerators. These emit radiation that is able to penetrate deeply into food, killing insect pests and microorganisms without raising the temperature of the food significantly.

Why in the world would anyone want to irradiate food?
Food is most often irradiated commercially to extend shelf-life, eliminate insect pests, or reduce numbers of pathogenic microorganisms. Food irradiation for these purposes is practiced in many countries, including the United States.

Can you tell me a bit more about how radiation is able to do this without causing a problem in the food?
Certainly. First, the food is packaged in a manner that permits the irradiation facility to deliver a precise radiation dose over the entire food package. The radiation strikes the chemical bonds in the food and forms stable products, much like what happens when you cook food. Many years of research has shown that the chemical by-products in food that has been exposed to high doses of ionizing radiation are the same by-products that appear during conventional cooking or other preservation methods.

Sounds kind of experimental to me. Why do we need another form of food processing other than those we already have available?
Actually, food irradiation is not new, and is definitely not experimental. The Food and Drug Administration, or the FDA, first approved irradiation as a preservation method in 1963. However, at that time, its application was confined to wheat and wheat flour for the purpose of limiting the growth of insects and microorganisms. Since then, it has proven to have other valuable applications as well.

Isn't food irradiation better suited for food being shipped long distances in ships and barges?
Not really. It is indeed a good application for foodstuffs being shipped and stored for a long time but it has more wide-spread applications than just shipping. For example, beef is consumed in great quantities in the U.S.; more than 8 billion pounds per year. Unfortunately E.coli, a potentially-deadly bacteria, has been found in beef in concentrations that are higher than any of us thought possible.

Is that the bacteria that was linked to the deaths of four children and the illness of hundreds of people in the Pacific Northwest?
Yes. If you recall, in 1997, Hudson Foods voluntarily recalled 25 million pounds of hamburger containing E. coli; the largest recall of meat products in U. S. history.

Wasn't that just a freak occurrence.
Unfortunately, it wasn't. Nationally, E.coli is responsible for over 20,000 illnesses and 500 deaths per year (CDC). However, this microorganism has only been linked to illnesses in humans since 1982.

Are there any other illnesses I should be concerned about?
Yes, there are a few others that are troubling. Salmonella, commonly found in poultry, eggs, meat and milk, and is responsible for the illness of over four (4) million people. Salmonella poisoning can be fatal as well. In fact, a report by the President's staff issued in May of 1997 indicates that millions of Americans are stricken by food borne illness like E.coli and Salmonella each year, and that as many as 9,000, mostly the very young and elderly, die as a result.

What did the government do in response to that report?
In December of 1998, the FDA approved the irradiation of red meat with a measured dose of radiation. This level of radiation exposure is very effective at killing E.coli and other disease- causing microorganisms in meat.

So if irradiation is so useful, does that mean that restaurants and grocery stores won't have to be as careful about cleanliness and refrigeration?
No. FDA officials are quick to point out that irradiation is a useful tool for reducing the risk of food-borne disease but it does not replace proper food handling practices by producers, processors and consumers.

How much radiation exposure does it take to sterilize food?
The FDA has approved specific doses to be applied to different foodstuffs. In general, a "low" dose (i.e. less than 1,000 grays) is used to delay physiological processes like ripening or sprouting of fresh fruits and vegetables. Low doses are also useful for controlling insects and parasites in food. A "medium" dose (i.e. from 1,000 to 10,000 grays) is used to reduce spoilage and extend the shelf life of many foods. A high dose (i.e. greater than 10,000 grays) is used to sterilize meat, poultry, seafood and other prepared foods.

Can you give me some examples?
Sure. A good example is irradiation of fresh pork to a dose of 300 gray. This fairly low level is able to completely control trichinella spiralis in this product. Here are a few other examples: Fresh foods irradiated to 1,000 gray inhibits growth and maturation; Poultry irradiated to 3,000 gray, refrigerated meat irradiated to 4,500 gray or frozen meat irradiated to 7,000 gray controls pathogens; dry spices and seasonings irradiated to 30,000 gray controls eliminates microbial infection.

What about super-high doses?
Well, there is a National Aeronautical and Space Administration (NASA) requirement that the frozen foods given to the astronauts be completely sterilized. These products receive about 44,000 gray.

These numbers seem awful high. How much radioactivity remains in the food after the irradiation, and how much of it would I actually ingest if I ate irradiated food?
Absolutely none. The radioactive material like cobalt-60 and cesium-137 used in the irradiation facility emits gamma rays. The food itself never comes in contact with the radioactive material. Instead it is simply "struck" by the gamma radiation.

I'm not sure I follow that. Do you mean once the food leaves the vicinity of the radiation source it is not radioactive?
Sort of. It actually never becomes "radioactive". It is simply "irradiated". Think of how you cook food on the gas stove. The food is surrounded by the radiant heat from the gas source for enough time to cook your steak the way you like it (i.e., rare, medium). to taste. However, no gas enters the meat, and once the food cools off, all of the gas "energy" is gone.

How do I know that something has been irradiated before I buy it a the grocery store?
The FDA requires a label to be placed on packages that have been irradiated. That label contains the Radura logo. They also require a statement that the food has been irradiated, has been "Treated by irradiation" or has been "Treated with radiation".

I don't know. I'm still not convinced. Has anybody else studied the possibility of a problem with the food?
Many national and international committees, organizations and regulatory agencies have reviewed the safety of irradiated foods. These include the World Health Organization (WHO), the Food and Agricultural Organization of the United Nations (FAO), the Codex Alimentarius Commission, and the U.S. FDA. They have all concluded that food irradiation is safe when Good Manufacturing Practices (GMPs) and Good Irradiation Practices are used. For the evaluation of safety, three main areas of concern were addressed: potential toxicity, nutritional adequacy, and potential microbiological risk. Information regarding the chemical structures and the amounts of radiolytic products in particular food types, together with the information obtained from toxicological testing, forms a sound basis for evaluating the toxicological safety of an irradiated food. Scientists have repeatedly concluded that the animal feeding studies have found no toxic effects from irradiated foods. Therefore, irradiation of food does not lead to changes in the composition of the food that, from a toxicological point of view, would have an adverse effect on human health.

Is there any place I can look for additional information on this topic?
Absolutely! We encourage you to visit the "Tool Box" section of the IEM web page. In the category entitled "Bibliography", we have listed some references that you may wish to review.

How about web sites?
There are lots of those too. For example, the FDA has several papers on the subject. You can read them at http://vm.cfsan.fda.gov/list.html; http://vm.cfsan.fda.gov/~lrd/hhsirrad.html; http://vm.cfsan.fda.gov/~lrd/fr990224.html; http://vm.cfsan.fda.gov/~dms/qa-fdb33.html; and http://vm.cfsan.fda.gov/~dms/opa-fdir.html.

Any more examples?
Absolutely. Here are just a few that are worth a few minutes of your time. You can read about the TTen most commonly-asked questions about food irradiation" at http://www.physics.isu.edu/radinf/food.htm#food1. The "Policy of the American Medical Association (AMA) on Food Irradiation" can be found at http://www.physics.isu.edu/radinf/food.htm#ama. The International Atomic Energy Agency's "Facts About Food Irradiation" is located at http://www.iaea.or.at/worldatom/inforesource/other/food/index.html. You can take an "Inside Look at Food Irradiation", courtesy of the Grocery Manufacturers of America, by visiting http://www.iaea.or.at/worldatom/inforesource/other/food/index.html. The Mayo Clinic has posted a write-up entitled "Food Irradiation: The Answer to E.Coli?" at http://www.mayohealth.org/mayo/9709/htm/food_irr.htm. And finally, the USDA has an annotated bibliography of food irradiation references at http://warp.nal.usda.gov/fnic/pubs/bibs/gen/foodirrad.html.

Anything else?
Yes. The "Tool Box" section of the IEM web page, under the category of "Bibliography", lists some excellent food irradiation references. You might want to scan through a few of those in your spare time.

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