Food Irradiation in Canada

Food Irradiation - Can Ionizing Radiation Technique Improve Food Quality and Safety?

Iain Chan PhD Physics , Jim Chan (Certified Public Health Inspector, Canada)

The Canadian government has recently authorized the use of ionizing radiation as a technique to extend the shelf life of raw ground beef and to reduce the number of microbes

such as bacteria, molds, parasites in raw ground beef. Like milk pasteurization and food canning, irradiation, according to the Canadian Nuclear Association (CNA) , is another method that can make food safer for the consumer and can enhances food quality and promoting less food waste. Ionizing radiation was previously regulated in Canada for use in the prevention of potatoes and onions from sprouting in storage, to kill insect infestations in wheat and flour and to reduce microbe populations in seasonings. United States has permitted the irradiation of fresh and frozen ground beef since 1999 and the U.S. Food and Drug Administration (FDA) has evaluated the safety of irradiated food for over 30 years and found the process to be safe. A variety of food approved by FDA for irradiation process including beef and pork, crustaceans, fresh fruits and vegetables, poultry, shell eggs, shellfish, spices and seasonings.

How is food irradiated and does irradiation make foods radioactive?
The term radiation can be intimidating to some people, but is different than something that is radioactive. While a radioactive source is used in some techniques, food products do not come into contact with radioactive material and do not become radioactive after processing.

In order to kill microbes, the food product is bombarded with ionizing radiation which knocks an electron out of an atomic or molecular orbit producing charged particles (ions) referred to as free radicals. These radicals damage the DNA of microbes so that they cannot reproduce. As a result, the growth rate of microbes is inhibited so that they are less effective at spoilage/causing illness.

How is food irradiation regulated?
In Canada, the Canadian Food Inspection Agency (CFIA) is responsible for the enforcement of regulations relating to irradiated food products under the Food and Drugs Act and regulations state the maximum dose of ionizing radiation that can be applied to food and the foods that may be irradiated and sold in Canada.

How does food irradiation work?
The standard measurement unit for a dose of radiation is called a Gray (Gy), and is the amount of absorbed energy per kilogram of mass. One Gray is equal to 1 Joule (J) of energy per kilogram (kg) of mass. For fresh raw ground beef the maximum dose is 4.5 kGy which is equal to 4500 Joules/kg. For fresh frozen ground beef the maximum dose is 7.0 kGy, or 7000 Joules/kg.

There are three types of ionizing radiation that have been approved for use on raw ground beef:

1. Gamma radiation which is a type of high energy electromagnetic radiation produced by the decay of radioactive elements. Gamma radiation has a high penetrating power which has the advantage of treating large quantities of ground beef at once. However, the high penetrating power means that lots of shielding is required in order to ensure that workers are not exposed. Two radioactive sources have been approved for use: Colbalt-60 (⁶⁰Co) and Cesium-137 (¹³⁷Cs). Cesium-137 produces gamma ray photons with an energy of 0.662 MeV (0.662 million electron volts) and Colbalt-60 produces two gamma ray photons: one with an energy of 1.17 MeV (1.17 million electron volts) and one with an energy of 1.33 MeV. 

2. X-ray radiation which is also a type of high energy electromagnetic radiation, but unlike gamma radiation can be produced using non-radioactive sources. X-ray radiation is produced by bombarding a metal target (such as gold) with a beam of electrons. When electrons hit the metal target they loose energy due to their rapid deceleration, and this energy is released as x-ray radiation. The maximum energy of the x-ray photons is equal to the energy of the electron beam, which regulations limit to 7.5 MeV for gold or tantalum metal targets and 5.0 MeV for other metal targets. X-ray radiation has a high penetrating power, so large quantities of ground beef can be irradiated at once. 

3. Electron beam radiation Beam of high energy electrons produced by heating an electron source (a cathode) and applying a high voltage in order to accelerate the released electrons. The maximum energy allowed for the electron beam is set at 10 MeV. While this is a higher energy than gamma or x-ray radiation, electrons have a much lower penetrating power and are suited for treating thin samples of food.

How can consumers be able to tell what food has been irradiated?

Health Canada is responsible for regulations specifying which foods may be irradiated and the treatment levels permitted.

See the table below for the foods which may be irradiated and sold in Canada (Health Canada - Food Irradiation)

The labelling regulations as outlined in the FDR  specified that label on product package or display sign of bulk irradiated food must clearly identify and reveal the food has been irradiated with both a written statement includes words such as irradiated, treated with radiation or treated by irradiation and the international symbol. 

What food safety messages consumers need to remember about irradiated food such as ground beef?
Irradiated raw ground beef does not guarantee zero risk as the process greatly reduces microbes, including pathogenic bacteria such as E.coli O157:H7, Salmonella, Campylobacter, and parasites which can cause food borne diseases, to enhance food quality by extending product shelf-life and creating less food waste. However, irradiated raw ground beef can sill contain pathogen and consumer can be infected by handling raw ground beef without washing hands afterwards and by eating undercooked ground beef. Consumer must remember to handle, store and process food properly, cook ground beef to a safe internal temperature (CFIA)  and always apply the rules of safe food handling to prevent foodborne diseases. 

References

1. M. Rocelle S. Clavero, J. David Monk, Larry R. Beuchat, Michael P. Doyle and Robert E. Brackett, Inactivation of Escherichia coli O157:H7, Salmonellae and Campylobacter jejuni in Raw Ground Beef by Gamma Irradiation; Applied and Evironmental Microbiology, Vol. 50 No. 6, page 2069, June 1994
2. Frances Elizabeth DeRuiter and Johanna Dwyer, Consumer acceptance of irradiated foods: dawn of a new era?; Food Service Technology, Vol 2, page 47, June 2002
3. Government of Canada Website: http://gazette.gc.ca/rp-pr/p2/2017/2017-02-22/html/sor-dors16-eng.php
4. World Health Organization Report: http://apps.who.int/iris/handle/10665/39463

Media links

CBC News Health Canada approves sale of irradiated ground beef, says can reduce bacteria

Health Canada clears ground beef irradiation Process meant to 'complement' but not replace food safety practices

The Canadian Nuclear Association (CNA) Food Irradiation