Irradiation A Hot Topic

Irradiation is a technique that exposes food to electron beams or gamma radiation, a high-energy light stronger than the X-rays your doctor uses to make a picture of your insides. Gamma rays are ionizing radiation, the kind of radiation that kills living cells. Ionizing radiation can sterilize food or at least prolong its shelf life by i Killing microbes and insects on plants (wheat, wheat powder, spices, dry vegetable seasonings)

i Killing disease-causing organisms on pork (Trichinella), poultry (Salmonella), and ground beef (pathogenic E. coli)

i Preventing potatoes and onions from sprouting during storage i Slowing the rate at which some fruits ripen

Irradiation does not change the way food looks or tastes. It does not change food texture. It does not make food radioactive. It does, however, alter the structure of some chemicals in foods, breaking molecules apart to form new substances called radiolytic products (radio = radiation; lytic = break).

Are irradiated foods harmful?

Many scientific organizations, including the 27,000-member Institute of Food Technologists and an international Expert Committee on the Wholesomeness of Irradiated Foods (which includes representatives from the United Nations, the International Atomic Energy Agency, and the World Health Organization), believe that irradiation is a safe and important weapon in the fight against food poisoning caused by microbial and parasitic contamination.

The Food and Drug Administration has been approving various uses of food irradiation since 1963. In addition, irradiation is approved for more than 40 food products in more than 37 countries around the world.

Some consumers, however, remain leery of irradiation, fearful that it may expose them to radiation (it can't; no radioactive residues are present in irradiated food) or that URPs (unique radiolytic products) — compounds produced only when foods are irradiated — may eventually turn out to be harmful. For now, irradiated food seems safe, but it's fair to point out that the story of irradiating foods is still unfolding, a situation that makes many people uneasy. For example, the

FDA's 2003 decision to allow irradiated ground beef into the National School Lunch Program has triggered debates in many school districts; several — including Los Angeles and the District of Columbia — have simply banned irradiated foods from their menus.

Around the world, all irradiated food is identified with this international symbol. Just in case that isn't enough to get the message across, the package must also carry the words "treated by irradiation" or "treated with irradiation." The only exception is commercially produced food that contains some irradiated ingredients, such as spices. The symbol and/or wording isn't required, for example, on the packaging for a frozen pizza that's seasoned with irradiated oregano.

About 90 percent of all compounds identified as radiolytic products (RP) also are found in raw, heated, and/or stored foods that have not been deliberately exposed to ionizing radiation. A few compounds, called unique radiolytic products (URPs), are found only in irradiated foods.

You can get answers online to the most commonly asked questions about food irradiation at the Web site maintained by the Centers for Disease Control (CDC): irradiation.htm.

Table 21-2 tells you when certain irradiated foods were deemed safe in the U.S.

Table 21-2 Foods Approved for Irradiation in the U.S.


Approval date

Wheat, wheat flour


White potatoes




Fruit and vegetables (fresh)


Herbs, spices, vegetable seasonings


Poultry (fresh, frozen)

1990 (FDA), 1992 (USDA)*

Animal/pet food


Meat (uncooked, chilled, frozen)

1997 (FDA), 2000 (USDA)*

Mollusks/seafood (fresh, frozen)


Ready-to-eat, unrefrigerated

meat/poultry products


Fresh eggs (in shell)


Seeds for sprouting


* Both the FDA and the USDA must approve treatment of meat and poultry ** Application awaiting FDA approval Federal Centers for Disease Control

* Both the FDA and the USDA must approve treatment of meat and poultry ** Application awaiting FDA approval Federal Centers for Disease Control

Is that food still good to eat? Understanding the dates on food labels

The following terms can help you figure out whether you should check whether your food's still good or whether you should just pitch it:

1 Sell-by: The last date on which the food can be offered for sale. If stored properly, most perishable foods such as milk, cheese, and packaged meats are safe for a few days past the "sell by" date.

1 Best if used by or Use by: Refers to the food's flavor and quality, not its safety; the manufacturer's recommendation of the last date on which the food is likely to taste best.

1 Expires or Do not use after: The last date on which a product either provides the highest nutritional value or works best (for instance, the last date on which yeast or baking powder is likely to make your bread or cake rise).

1 Packing date: Used on eggs from USDA-inspected facilities to show the date on which the eggs were packed. The date is written as a number from 1 (January 1) to 365 (December 31 — except in a leap year, naturally). Eggs from USDA-inspected plants may also carry an expiration date.

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