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Center For Consumer Research - Food Irradiation
 
What is Food Irradiation?
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What Foods Can Be Irradiated

What is Food Irradiation?
    - What is Food Irradiation?
    - How does Food Irradiation work?
    - Why irradiate foods?
    - How do irradiated products taste?

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Myths about Food Irradiation

Are Irradiated Foods in the Supermarket?
    - Are Irradiated Foods in U.S. Supermarkets Now?
    - Is This Technology Being Used in Other Countries?

Food Irradiation Safety Issues
    - Is Irradiated Food Safe?
    - How is Safety Tested?
    - Does Nutritional Value Change After Irradiation?
    - Are There Hazards with Food Irradiation?
    - Are Irradiated Foods Labeled?

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Consumer Acceptance of Food Irradiation

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Updated: May 07, 2000

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What is Food Irradiation? How does Food Irradiation work?
Why irradiate foods? How do irradiated products taste?
How does Food Irradiation work?


Food is exposed to a carefully measured amount of intense ionizing radiation. This is done in a special processing room or chamber for a specified duration. With food irradiation, radiant energy (electrons, gamma rays, or x-rays) breaks chemical bonds, leaving the food still like-fresh, but with specific benefits, depending on treatment level.

Place mouse over the keyword to read the description of its functionality. (Using Internet Explorer 4.0 or Netscape 6.0)

 [Irradiation Machine] When the cobalt is in the water, people can safely enter the irradiation room. During processing boxes of 
food pass around cobalt 
source, receiving the gamma 
ray treatment. Cobalt is shielded under 
water in an underground 
tank when not in use. Treatment is controlled by the
speed of the conveyer belt. 
Amount of energy needed varies
by the density of the load Packaged food is loaded onto
a conveyer belt for treatment Treated food can be 
handled immediately.  
The fence keeps treated 
and untreated food 
separate Concrete walls prevent gamma
rays from escaping into the 
environment

Types of Facilities


Cobalt 60, Gamma Facility  [Irradiation Plant]
The most common source of ionizing energy is cobalt 60. This radioactive material is contained in two sealed stainless steel tubes (one inside the other - double encapsulated) called "source pencils." These are placed in a rack and the entire rack is immersed in a water chamber underground when not in use. When irradiation takes place, the rack is raised. Packaged food products move along the conveyer belt and enter an inner room where they are exposed to the rack containing source pencils. Energy in the form of gamma rays (or photons) pass through the encapsulation and treat the food.


Electronic Beam Facility (E-Beam)
Irradiation source is a machine that generates electrons. Electrons are accelerated. A magnet directs the electrons. A curtain of electrons flow over the product.
The Electron Beam Linear Accelerator, (E-beam) Accelerators work on the same principle as a television tube. Instead of being widely dispersed and hitting a phosphorescent screen at low energy levels, the electrons are concentrated and accelerated to 99% of the speed of light. This produces rapid reactions on the molecules within the product. The Electron Beam Linear Accelerator machine generates and accelerates electrons to energies of 5,7.5 or 10 MeV (Million electron volts) with beam power of up to 10 kW.  [ E-Beam Treatment ]
Meat receiving e-beam treatment
Click for Large Picture
 [ Accelerator Facility ]
Linear Accelerator Facility
Click for Large Picture
Insulation to shield workers from electron energy. Insulation to shield workers from electron energy. A conveyer belt moves packages of ground beef through the facility. An electron gun focuses the electrons over the product from the top. Another electron gun focuses electrons on the bottom of the product.
A Conveyer or cart system moves the product to be irradiated under the electron beam at a predetermined speed to obtain the desired dosage. Products move in and out of the irradiation area continuously. Product thickness depends on density and electron energy. For example, e-beam energy can penetrate meat a total of 3.5 inches with treatment on the top and bottom of a package.


X-Ray Facility
Food can also be irradiated by X-rays. In this sytem an electron beam accelerator targets electrons on a metal plate. Some energy is absorbed and the rest is converted to X-rays. Like gamma rays, X-rays can penetrate food boxes up to 15 inches thick or more, thus permitting food to be processed in a shipping container.


When food is irradiated, most of the radiation passes through the food without being absorbed. The small amount that is absorbed destroys any insects on grains,produce or spices, extends shelf life, and prevents fruits and vegetables from ripening too fast. Thus, food irradiation may replace chemical fumigants, sprout inhibitors, and post harvest fungicides. Higher doses can kill Salmonella and other harmful bacteria that can contaminate meats and poultry and cause food borne diseases.

Food irradiation is a "cold treatment" that achieves its effects without raising the food's temperature significantly, leaving the food closer to its original state. Even spices which are treated for 2-4 hours remain essentially at room temperature. By not using high temperatures, food irradiation minimizes nutrient losses and changes in food texture, color, and flavor.

The energy used in food irradiation is not great enough to cause food to become radioactive. During irradiation, energy passes through food much like a ray of light passes through a window. This energy destroys most of the bacteria that can cause disease, yet allows food to retain its high quality.

Irradiation pasteurizes food by using energy, just as milk is pasteurized using heat. At the level used, most harmful bacteria will be destroyed. Afterwards, surviving bacteria could start to multiply if the food were mishandled: such as, stored at an improper temperature. The level of irradiation used also does not kill certain spoilage organisms. This is for the protection of consumers. Spoilage bacteria will multiply and alert consumers not to use a product which has been improperly handled.

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 multiply.

Facility Safety
Water is used to shield the cobalt when it is not in use. The water is not radioactive.  [Glowing Cobalt]

 [Lab] Irradiation facilities must include many safety features to prevent both environmental and worker exposure. The use and transportation of radioactive materials - including the equipment and the facilities in which they are used -- are closely monitored by the Nuclear Regulatory Commission, state agencies, and the Department of Transportation.

A food irradiation plant is not a nuclear reactor. In a reactor, a nuclear chain reaction takes place, heat is generated and used to make steam which turns a turbine and creates electricity. Proper controls are needed to contain the chain reaction and maintain proper cooling. A food irradiator is completely different.

The effects of treatment by e-beam, cobalt 60, cesium 137 are identical. Use of one method or another is based upon product size, facility size, anticipated throughput, and other factors.