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.
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60, Gamma Facility
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
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.
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.
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.
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.
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.
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.
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.
is used to shield the cobalt when it is not in use. The water
is not radioactive.
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.
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.
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.