Course:FNH200/Lessons/Lesson 10/Page 10.3

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10.3 What is Food Irradiation?

Food Irradiation is the application of radiation, in the form of ionizing energy, to foods. According to Health Canada, Food Irradiation means "the treatment of food with ionizing radiation" from the following sources:

  • Gamma radiation from a Cobalt-60 or Cesium 137
  • X-rays generated from a machine source operated at or below 5 MeV
  • Electrons generated from a machine source operated at or below 10 MeV

(read the full definition in Division 26 (Links to an external site.) of the Food and Drug Regulations)
Important Definitions pertaining to food irradiation:

  • Gamma radiation is electromagnetic radiation that has very short wavelengths, similar to "short" x-rays. Isotopes such as cobalt 60 and cesium 137 emit gamma radiation as they disintegrate. The energy level of the gamma radiation emitted by these isotopes will not induce radioactivity in food materials.
  • X-rays are electromagnetic radiations that are highly energetic and of short wavelength. X-rays are produced by x-ray machines that emit a beam of fast electrons which hit a metal target in a vacuum. X-ray machines emit radiation only when the machines are turned on.
  • Electrons with high-energy (speed) may also be generated by an electron beam accelerator. Electron Beam Accelerators need only electricity to operate and produce no waste materials
  • The Gray is a unit of energy absorbed by a food irradiated with ionizing radiation. One gray (Gy) is equivalent to the absorption of 1 joule of energy by 1 kilogram of food. One thousand grays equals one kilogray (kGy). Most of the ionizing radiation processes permitted around the world involve absorbed doses of <10 kGy.
  • The Rad is another unit used to express the radiation absorbed dose (rad), where 100 rads = 1 Gy. However, the preferred unit is the kGy (above)

Atomic Energy of Canada Limited (AECL) is a Canadian federal crown corporation that is a leading agency in the development of food irradiators that use cobalt 60 as the energy source. The Canadian Nuclear Safety Commission (CNSC) (formerly the Atomic Energy Control Board or AECB) regulates the use of nuclear energy and material in Canada.

  • Cobalt 60 is produced in the Canadian-built Candu reactors. It is contained within the stainless steel rods that are used to control the rate of nuclear fission and as such is not extracted from spent nuclear fuel. In this context, the cobalt is housed within stainless steel rods which are transported to a facility near Ottawa where the cobalt 60 pellets within the rods are recovered and then reassembled in stainless steel rods to be used as the energy source in food irradiators and also irradiators for sterilizing medical supplies (bandages, specimen containers) and devices, or for use in irradiators utilized for cancer therapy.
Figure 10.2 Diagram of a food irradiation facility. In such a facility, cobalt 60 (Co 60) would be used as the source of ionizing energy.

Figure 10.2 shows a typical diagram of an irradiation facility. In such a facility, the food is pre-packaged in boxes that are loaded into a pallet carrier where a conveyor system moves the food in the pallets. The pallets are carried into a chamber with irradiation source (eg. Cobalt 60). The pallet carriers travel through the irradiator room and around the Cobalt 60 source at a speed such that the required absorbed dose is attained. The absorbed dose depends on the amount of time food is exposed to the irradiation source. Dosimeters are placed with the food to measure the dose received (absorbed) in kGy. The irradiated pallets of food exit to the unloading station which is physically separated from the loading station so that treated and untreated foods do not become intermixed. A similar process is used with e-beam guns, where the food is carried through conveyor belts and passes through the electron beam. Please watch this video where they show food being irradiated using e-beam

Where are the (food) irradiation plants in Canada?

Most of the irradiation facilities in Canada process medical and personal care supplies. MDS Nordion (Laval, Quebec) and Iotron (Port Coquitlam, BC) process some dry food ingredients. The former uses gamma rays, while the latter uses electron beam technology. The Canadian Irradiation Centre (CIC) is a training centre operated as a joint venture by MDS Nordion and the Université du Québec, Institut Armand-Frappier (IAF).