Course:FNH200/Lessons/Lesson 10

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Preservation of Food with Ionizing Energy

10.0 Overview

The exposure of food to ionizing energy, more commonly known as food irradiation, is a preservation technology that has generated much public debate. In this lesson you will learn important definitions relating to this technology. The types and sources of ionizing energy and irradiator layout will be introduced. You will learn about the current regulations regarding the use of ionizing energy for food preservation in Canada and in other countries. We will explore a number of issues and controversies about the use of ionizing energy in the food industry. This lesson provides you a sound understanding of ionizing energy as a preservation technology and introduces you to the issues that have been raised in the popular press.


Upon completion of this lesson you will be able to:

  • understand the concept of food irradiation as a food preservation method;
  • outline the terminologies commonly used in conjunction with preservation of food with ionizing energy
  • describe the principles for determining the required irradiation dose depending on the desired outcome
  • illustrate the principles for determining wholesomeness and safety of irradiated foods
  • summarize the regulations, and compare the magnitude of food products that are approved for irradiation in Canada versus United States of America
  • articulate a personal set of values pertaining to the use of ionizing energy in food preservation

Optional Reading

10.1 Introduction

Terms to remember

  • Electromagnetic spectrum
  • Ionizing energy
  • X-rays, gamma and beta rays
  • Division 26 of the Food and Drugs Act and Regulations
  • MeV, kGy
  • Free radicals
  • Unique radiolytic products
  • Radurization, Radicidation and Radappertization
  • Radura symbol

Aside from the use of genetically modified organisms in foods, there is perhaps no other method of food preservation that has generated as much heated debate recently as food irradiation. Although the basic concept of food irradiation as a food preservation technology is not new (a patent for food preservation by irradiation was applied for in the United States in 1921), it is nonetheless a controversial method of food preservation.

Much of the controversy about food irradiation seems to stem from a fear of the unknown and unfamiliar - we have often seen references in media reports of food irradiation associated with radioactive fallout, accidents at nuclear power plants and concerns about nuclear war and weapons testing. This has led to further confusion in the minds of the general public about food irradiation and what the process actually involves. Upon completing this lesson, you will have a good knowledge of what food irradiation is, what its potential applications are, the physical process of food irradiation, and limitations and advantages of food irradiation as a method of food preservation.

10.2 What is Radiant Energy?

Radiation refers to the emission and propagation of energy through matter or space by electromagnetic disturbances. These forms of energy are found within the electromagnetic spectrum of radiation (Figure 10.1). This is an organized scale where we find energy ranging from radio waves, microwaves, visible light to ionizing radiation. These forms of energy vary in frequency, wavelength, energy value, penetrating power, and their effects on biological systems.

Figure 10.1. The Electromagnetic. SpectrumAdapted from: Purves et al., 1992. Life The Science of Biology (3rd ed.), Ch. 8. Sinaur Associates, Inc., Sunderland, Mass., p. 164

The longer wavelengths of electromagnetic energy that we are familiar with include visible light, infrared and ultraviolet rays. These are characterized by having low penetrating power. Microwaves and infrared radiation are two examples of the longer wavelengths in the electromagnetic spectrum.

  • Microwaves are used in food for their heating properties. The microwaves travel in straight lines and pass through air, glass, paper and plastic, but reflected by metals. They are readily absorbed by water (polar molecule), causing it to vibrate. Heat is generated by the intermolecular friction generated from the vibrating water (polar) molecules in food. Microwaves are absorbed by food up to a depth of 5 to 7.5 cm.
  • Infrared energy can generate heat. They can reach temperatures above 100°C. Typical examples of infrared energy can be seen in ovens, toasters, and even those "infrared" lamps used to keep food warm.

Examples of short wavelengths include X-rays, beta rays and gamma rays, which can be employed as energy sources in food irradiation, since they have good penetrating power. These forms of energy are referred to as ionizing energy.

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).

10.4 Effects of Ionizing Energy Absorbed by Food - Preservation principle

The basis of food preservation by treatment with ionizing energy is the ability of the absorbed quanta of energy to dislodge electrons from molecules with the concomitant creation of free radicals without inducing radioactivity in the food.

When ionizing energy from a permitted source for food use is absorbed by food and collides with a molecule or atom, an ion-pair is produced if the energy from the collision is sufficient to dislodge an electron from an atomic orbit. This phenomenon can lead to breaking up of one or more bonds between atoms in the molecule, leading to new molecular fragments possessing unshared electrons (free radicals). Because of the unshared electron, free radicals are extremely reactive and tend to react with other free radicals or other molecules with unshared electrons.

It is believed that only one out of every six billion chemical bonds in bacteria or food molecules are broken by irradiation. However, the formation of ion pairs and free radicals, the reaction of free radicals with one another or other molecules, and the chemical and physical phenomena that occur as a consequence of these events form the mechanisms for the inactivation of microorganisms, enzymes and alterations of food constituents during food irradiation.

The changes induced in food by absorption of ionizing energy can arise from both direct and indirect effects. Please read the required reading Irradiation and Food Safety for details. You will note that many of the effects observed in foods arising from the absorption of ionizing energy are due to indirect effects as explained in the optional reading. This is shown below:

Figure 10.3

Hydrogen, hydrogen peroxide and hydroperoxy free radicals are produced when ionizing energy is absorbed by foods (fruits, vegetables, meats, fish) that contain substantial quantities of water. Figure 10.3 shows the reactions of hydrogen (H) and hydroxyl (OH) free radicals produced by gamma irradiation of water molecules. These free radicals only exist for about 0.0001 seconds, but generate hydrogen peroxide (H2O2) which is the antimicrobial agent that kills bacteria, yeasts, and moulds in foods. In many cases, the free radicals are formed within the microbial cells.

As mentioned earlier, microorganisms may also be killed by a "direct effect" of the ionizing energy upon genetic material within the microbial cells that leads to the death of the microorganism. As mentioned in the required reading (Irradiation and Food Safety) "the damage occurring from ionizing radiation can be random and extensive, making DNA repair near impossible". In some cases, even relatively small changes in the DNA can destroy bacterial cells, and the disruption of genetic material in living cells by irradiation also enables the destruction of insects, inactivation of parasites, delaying of ripening, and prevention of sprouting.

Are Free Radicals Unique to Irradiated Food?

A concern that has been expressed in regard to the use of food irradiation is the generation of free radicals during exposure of the food to ionizing energy.

It is true that free radicals are produced in foods during irradiation. However, the free radical formation is not unique to foods which have been irradiated with ionizing energy. For example, oxidative reactions in foods containing unsaturated fats also involve free radical formation, and free radicals are also formed during the course of the Maillard browning reactions. Free radicals are also produced within our bodies and other living tissues during normal metabolism. Mechanisms (chemical and enzymatic) for inactivation of free radicals exist within the human body and other living tissues.

Does irradiated food become radioactive?

Irradiation using approved sources provides enough energy to knock an electron from the outer orbit (that is why it is termed "ionizing radiation" or "irradiation"); however, it does not have sufficient energy to penetrate the nucleus and eject neutrons, which would be required to induce radioactivity. Therefore food will NOT become radioactive by irradiation conducted using approved energy sources and within the approved limit. To become radioactive, food would need to be exposed to a minimum of 15 MeV of energy. The energy output of Cobalt 60, Cesium 137, and e-beam accelerators is carefully regulated. The maximum energy outputs allowed are 5 or 10 MeV, which are too low to induce radioactivity in food.

You may be interested to know that all foods are naturally radioactive, although of course at a very low level. This low background level of radioactivity arises from the naturally occurring isotopes in elements such as carbon, phosphorus, potassium, and sulfur.

10.5 Changes that can Occur in Food during Irradiation

Another concern expressed about food irradiation is the possible formation of unique radiolytic products. However, in fact, the molecular changes in foods treated with ionizing energy are not usually unique or distinct from those found in non-irradiated foods such as those treated by thermal processing. The few unique radiolytic products that have been found are at such trace levels, that they are not considered to be of any significance, and so far toxicological studies have not found evidence of any harmful effects.

Other changes can occur in foods during irradiation with ionizing energy via indirect effects. These changes can involve the radiolysis of water molecules to produce reactive hydroxyl radicals, or reactions in foods of peroxides and peroxide free radicals with fats, leading to lipid oxidation(rancidity). Some vitamins are also sensitive to radiation. The extent of effects on both macronutrients and micronutrients are, of course, dependent on the dose of irradiation. Page 51 of Irradiation and Food Safety describes the effects of food irradiation on macro- and micro- nutrients. It also describes some of the sensory changes that have been perceived and their implications for the consumer.

Want to learn more?
  • Read: the IFT Scientific Status Summary on "Irradiation and Food Safety" by Smith and Pillai.
  • Try to answer the following questions (keep in mind the radiations doses being used):
    • What are the two groups of compounds (radiolytic products) that have generated concern?
    • Of these two groups, only one is considered as "unique radiolytic products" - which one?
    • What are the opinions of Health Canada and of the European Commission's Scientific Committee on Food on potential toxicity concerns based on mutagenicity/genotoxicity studies?
    • What was the role of Health Canada in the mutagenic/genotoxic studies?
    • Which nutrients are less sensitive to irradiation? Which are most sensitive?
    • What effects could irradiation have on sensory properties?

Below are three proposed methods of minimizing the "undesirable" changes during food irradiation:

Irradiation in the frozen state

  • When water is frozen free radicals are produced at a lesser extent
  • The frozen state will delay free radical diffusion and migration to food constituents beyond the site of free radical production.
  • However, as we learned in the required reading by Smith and Pillai (2004), the D10 values also change as the water in the product freezes.

Irradiation in a vacuum

  • Removing O2 from the system may minimize reactions; however,
  • Removal of oxygen could also confer a protective effect on microorganisms.

Addition of free radical scavengers

  • Ascorbic acid has a great affinity for free radicals.
  • Addition of free radical scavengers to food systems results in consumption of the free radicals via reactions between the scavengers and the free radical(s).

10.6 Irradiation Methods & Doses

Table 10.2 shows the absorbed doses required to achieve a variety of applications ranging from inhibition of sprouting to achieving commercial sterilization of a food commodity.

Table 10.2. Typical applications of ionizing energy for food preservation

Note: Includes examples that are not approved for use in Canada.

Dose (kGy) Purpose Examples
< 1 inhibit sprouting of vegetables

kill insects eggs, larvae

slow ripening

inactivate parasites





1 to 10 eliminate disease causing bacteria (Salmonella, E.coli O157:H7) and parasites

decrease or eliminate spoilage causing microorganisms (eg. mould)

chicken, ground beef, fruit and vegetables

fresh strawberries

10 to 50 kGy decontaminate food ingredients and additives

commercially sterilizes food

enzymes and spices

sterilized hospital diets, foods for use on missions in outer space

Radiation Pasteurization (radicidation, radurization) methods

Radicidation is defined as a process designed to kill or inhibit disease-causing microorganisms (such as vegetative bacteria, yeasts, parasites) in food. Absorbed doses are often below 10 kGy. Foods that have been treated with a radicidation dose of ionizing energy must still be stored under refrigeration since all spoilage-causing microorganisms would not have been killed.

Radurization, a form of radiation pasteurization, has as its objective the killing of the majority of spoilage-causing microorganisms and parasites so that storage life of the food can be extended during refrigerated storage. For example, treatment of fish to kill most of the spoilage-causing psychrotrophic bacteria would extend the storage life of the fish at refrigerated storage temperatures. Absorbed doses for radurization are below 10 kGy (often < 1 kGy).

Radiant Sterilization (radappertization) methods

Radappertization, equivalent to thermal commercial sterilization, involves treatment of food with an absorbed dose of ionizing energy such that disease-causing microorganisms and all spoilage-causing microorganisms capable of growing at the conditions of storage (e.g., at ambient temperatures) are inactivated. Absorbed doses of ionizing radiation are greater than (>) 10 kGy (usually 20, 30 kGy).

Note that in Canada, doses above 10 kGy are NOT permitted!

10.7 Factors affecting Food Irradiation

The factors that need to be considered and controlled during food irradiation include:

  1. Safety and wholesomeness of the foods
  2. Resistance of food to irradiation
  3. Resistance of microorganisms to ionizing energy
  4. Resistance of enzymes to ionizing energy
  5. Cost

10.7.1. Safety and Wholesomeness of Irradiated Foods

In Canada, the Health Products and Food Branch of Health Canada considers issues about safety and wholesomeness of irradiated foods, in addition to the safety and wholesomeness of foods preserved by other food preservation methods. The Canadian Food Inspection Agency considers aspects related to labelling of irradiated foods. The issues of safety and wholesomeness of irradiated foods revolve around criteria of the following four principles:

  • Radiological safety: ensuring that foods do not become radioactive during irradiation;
  • Toxicological safety: ensuring that production of toxic and possibly carcinogenic substances does not occur;
  • Microbiological safety: ensuring the efficacy of the radiation process with respect to the ability of the prescribed absorbed dose to kill disease-causing microorganisms that could be in the food.
  • Nutritional adequacy: ensuring that undue losses of nutrients do not occur as a consequence of treatment of food with ionizing energy; and

The conclusions drawn by the Canadian and international regulatory agencies about food irradiation are that foods treated such that the absorbed dose is below 10 kGy do not contain toxicants at undesirable levels. That is, the irradiated foods which have absorbed a dose of less than 10 kGy are wholesome and safe for long-term consumption.

In 1997, a Study Group was convened by the World Health Organization (WHO), the Food and Agriculture Organization (FAO), and the International Atomic Energy Agency (IAEA), to evaluate wholesomeness of food irradiated with doses above 10 kGy. In a report published in 1999, "The Study Group concluded that food irradiated to any dose appropriate to achieve the intended technological objective is both safe to consume and nutritionally adequate ... Accordingly, irradiated foods are deemed wholesome throughout the technologically useful dose range from below 10 kGy to envisioned doses above 10 kGy" (WHO Technical Report Series 890). Applying the concept of "substantial equivalence", even high-dose irradiated foods are considered to be as safe as foods sterilized by conventional thermal processing, such as canning of low-acid foods.

10.7.2. Resistance of Foods to Ionizing Energy

Not all foods are amenable to preservation by treatment with ionizing energy. The same can be said for thermal processing, freezing and dehydration as methods of food preservation. The quality of some foods may be adversely affected by irradiation, depending on the dose, temperature and conditions during irradiation. For example, colour, flavour or textural changes may result after exposure of food components to ionizing energy. Lipids or fats are particularly susceptible to oxidative reactions triggered by the radiolytic reactions and presence of free radicals. Losses of some vitamins may also occur; vitamins A, C, E and B1 (thiamine) are the most sensitive, particularly at higher doses and in foods packaged in air.

As mentioned above, these changes may be minimized by irradiating foods in the frozen state, in a vacuum, and/or with the addition of radical scavengers such as ascorbic acid. Additional strategies include applying the lowest effective irradiation dose and choosing appropriate packaging in terms of moisture and oxygen barriers.

10.7.3. Resistance of Microorganisms to Ionizing Energy

As in the case of thermal processing (pasteurization, commercial sterilization), microorganisms vary in their resistance to the killing effects of ionizing energy. Analogous to thermal processing where Clostridium botulinum is the most heat resistant pathogen, C. botulinum spores are the most radiation resistant forms of pathogenic bacteria.

You may recall that we discussed the decimal reduction time (D-value) in Lesson 6 in conjunction with thermal processing of foods. Similarly, it is possible to determine the dose of ionizing energy necessary to effect a 90% destruction of the particular microorganism in question. When we calculated the D-value in the lesson on thermal processing, we referred to the length of time at a constant temperature required to create a 90% decrease in the population of the microorganisms or spores in question. In irradiation concept, the time at a constant temperature could be converted to an absorbed dose of thermal energy.

With food irradiation, we calculate the absorbed dose of ionizing energy that produces a 90% decrease in the microbial population (D10 values). To achieve an appropriate margin of safety, a 5D or a 12D radiation treatment would have to be applied to acid and low acid foods, respectively. Although the source of the energy and the mechanisms by which microorganisms and spores are killed are different, the same concept (decimal reduction value) is applied during determination of the efficacy of thermal processing and preservation of food with ionizing energy.

Is it true that irradiation can mask food spoilage?

Irradiation cannot be effectively used to mask or cover up food spoilage since the microorganisms can be easily killed but the spoilage odours, off-flavours and colour changes caused by the spoilage microorganisms can not be changed or eliminated by ionizing radiation.

Thus, claims that ionizing radiation can be used to mask signs of poor quality in food are untrue.

What about Microbiological safety?

There has been concern about the creation of "superbugs" or mutants that are more dangerous but this is not a significant issue at the doses of ionizing radiation used in food processing.

Want to learn more?
  • Take a look at D10-values of some important foodborne pathogens, listed in Table 1 of the IFT Scientific Status Summary on "Irradiation and Food Safety" by Smith and Pillai:
  • The D10-values for E. coli 0157:H7 (in ground beef patties, at 5oC) and for Salmonella spp. (in turkey breast meat at 5oC) are 0.27-0.38 and 0.71 kGy, respectively.
    • What dose would be required for a 5D process for each of these pathogens under those conditions?
    • What dose would be required for a 12D process for each of these pathogens under those conditions?

10.7.4. Resistance of Enzymes to Ionizing Energy

The majority of food enzymes are more resistant to ionizing energy than spores of C. botulinum. The term DE (D-enzyme) is used to determine the radiation dose that produces a 90% reduction of enzyme activity. The DE values are of the order of 5 Mrad. Four DE values (5 x 4 = 20x106 rad1 or 200 kGy) would produce nearly total enzyme destruction; however, 200 KGy would also destroy many food constituents!

1Remember that 100 rad is equivalent to 1 Gray of absorbed ionizing energy and 1000 Gray equals 1 KGy.

From this calculation, you will have noted that enzymes cannot be easily inactivated by treatment with ionizing radiation. Ionizing energy could never be used for blanching vegetables. One of the concerns expressed by groups opposed to food irradiation is that enzymes in food are destroyed by exposure to ionizing energy. Clearly, from the example above, that is not the case especially if you consider the maximum dose permitted in Division 26 of the Food Regulations of Canada is 10 kGy.

If vegetables were to be preserved with ionizing energy, they would first have to be blanched with heat followed by treatment with ionizing energy to inactivate the microorganisms of concern.

10.7.5. Costs

After the issues of safety and wholesomeness have been satisfied, economic factors must be considered in evaluating the feasibility of an application of food irradiation. Food irradiation may be economically viable if it results in substantial increases in storage life and therefore marketing time and decreases in post-harvest or catching losses. This may be the case in terms of radicidation (discussed below) treatments of fresh fish or some fresh fruits. In cases where the process does not offer advantages (such as nutrition retention, technological advantages, economic advantages) it would not be economically viable.

10.8 Potential Applications of Radiant Energy

The following examples illustrate various potential applications of ionizing energy in food preservation:

  • Much of the food consumed by American and Russian astronauts has been preserved with ionizing energy.
  • Irradiation has proven effectiveness in the elimination of Salmonella from cut-up, packaged chicken. The chicken has received good consumer acceptance in test market trials in the United States.
  • Use of low dose radiation was approved in the United States, in December 1997, for general use in irradiation of ground beef to eliminate the bacteria (Escherichia coli O157:H7) that cause "hamburger disease".
  • A similar application is under consideration by Health Canada. There was a Public Information Session held on the UBC campus on January 16, 2003, in which information was provided on proposed amendments to allow irradiation of ground beef, poultry, shrimp and prawns, and mangoes. On June 18th, 2016 Health Canada proposed regulatory amendment to include fresh and frozen raw ground beef to the list of approved food for irradiation. UPDATE: Feb 2017, Health Canada has approved irradiation of fresh and raw ground beef. Please see table for complete up to date list of approved foods for irradiation.

10.9 Consumer Acceptance

The ultimate factor which will determine the economic viability of preserving foods with ionizing energy is consumer acceptance. In North America, the jury is still out as to whether radiation preserved foods would be accepted by consumers. Results of recent consumer surveys, described under "Consumer acceptance" in the Scientific Status Summary by Smith and Pillai, suggest acceptability rates ranging from 45% to over 90%. However, there are lingering "concerns expressed by anti-irradiation groups", including the use of food irradiation to overcome poor sanitation practices and environmental concerns related to irradiation facilities.

10.10 Regulations and Use of Ionizing Energy in Canada

As you noticed in the required reading (Irradiation and Food Safety), in the U.S. food irradiation is regulated as a "food additive". This is another good example of the differences that exist in the food additive definition between Canada and the U.S. (reviewed in Lesson 4).

In Canada, the use of ionizing energy for irradiation of food is considered as a process and is regulated underDivision 26 of The Food and Drug Act and Regulations. Note that the sources and energy levels of ionizing energy that would be permitted for use in Canada are clearly defined (Section B.26.001). Specified types of information would have to be submitted to the Health Products and Food Branch of Health Canada when an application is made to treat a specific food commodity with ionizing energy (B.26.004). Specific records would have to be maintained by a food processor employing ionizing energy (B.26.005).

The various options suggested for labelling of irradiated foods are presented in Section 2.14.1 of the "Guide to Food Labelling and Advertising (Links to an external site.)" from the CFIA. Note that in addition to the mandatory basic labelling (Lesson 4), food treated with ionizing radiation MUST also include:

  1. A statement indicating that the food has been "treated by irradiation", or "treated with radiation", or"irradiated".
  2. The "radura" symbol is also used to indicate that a food has been irradiated (see below).
  3. If an irradiated food is used as an ingredient of another food, it must be declared as "irradiated" in the ingredients listing only if it constitutes 10% or more of the final food.
Radura Symbol
Critical Thinking
  • What are the risks and benefits of the application of ionizing radiation or irradiation as a food preservation technology?
  • Conduct a quick search on the internet and view supporting and opposing views and critically evaluate their validity. What is your personal stand on irradiated foods?
  • Visit the Fact Sheet on Food Irradiation by the Canadian Food Inspection Agency. There is also a useful link at the end of the fact sheet to Frequently Asked Questions Regarding Food Irradiation on the Health Canada website.
    • The list of approved products is listed in a table in Division 26 of the Food and Drugs Act, Food and Drug Regulations. Note that approval does not necessarily mean that irradiation is actually being used for all of these approved products.
    • Check out the website of the Food Program of Health Canada for the current and proposed regulatory amendments to food irradiation provisions. The approval of new applications of irradiation undergoes a decision-making process similar to what we learned in Lesson 4 for approval of food additives.
    • Can you answer the following questions?
      • What foods are currently approved for treatment by ionizing radiation in Canada?
      • What is the purpose for each approved use, and what is the permitted absorbed dose?
      • What amendments are currently being proposed in Canada?
      • What are the Canadian regulations regarding labeling of irradiated foods or foods containing irradiated ingredients

10.11 Summary of Lesson 10

  • Food irradiation refers to the process of preserving food by using ionizing energy. In Canada, it is regulated under Division 26 of the Food and Drugs Act and Regulations.
  • Ionizing energy is characterized by having short wavelengths with high penetrating power. Examples of these forms of energy are X-rays, gamma and beta rays.
  • The energy emitted from these sources is measured in MeV. Whereas, the amount of energy absorbed by the food is measured in kGy.
  • Food will not become radioactive if the energy sources are operated at levels <15 MeV
  • The preservation principle of food irradiation involves a direct and indirect effect on microorganisms.
  • There are some oxidative changes as well as unique radiolytic products (ACBs, benzene, etc) that have been traced to certain irradiated food products.
  • Irradiation in the frozen state, under a vacuum or using antioxidants, are examples of mechanisms available to try and minimize these undesirable changes.
  • Depending on the absorbed dose, different irradiation methods can be achieved (radurization, radicidation and radappertization)
  • There are several factors that affect food irradiation (safety & wholesomeness, resistance of food, microorganisms and enzymes, as well as cost)
  • The safety & wholesomeness of irradiated foods is evaluated by the Health products and food Branch of Health Canada. It relies on 4 basic principles (radiological, toxicological and microbiological safety, and nutritional adequacy)
  • There are only certain foods currently approved for treatment by ionizing radiation in Canada.
  • There are specific labelling regulations for food treated with ionizing radiation


FNH 200 Course content on this wiki page and associated lesson pages was originally authored by Drs. Brent Skura, Andrea Liceaga, and Eunice Li-Chan. Ongoing edits and updates are contributed by past and current instructors including Drs. Andrea Liceaga, Azita Madadi-Noei, Nooshin Alizadeh-Pasdar, and Judy Chan.

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Permission is granted to copy, distribute and/or modify this document according to the terms in Creative Commons License, Attribution-NonCommercial-ShareAlike 3.0. The full text of this license may be found here: CC by-nc-sa 3.0

1. Ionizing energy preserves food indirectly by forming ... (Choose two)

Free radicals
Radiative food
Hydrogen peroxide, H2O2
Radiolytic products

2. Which regulatory agency is responsible for the labeling and advertising of irradiated foods in Canada?

Atomic Energy of Canada
Canadian Food Inspection Agency
Canadian Irradiation Centre
Canadian Nuclear Safety Commission

3. Choose the best definition of ionizing energy.

Energy that produces radioactivity in its target.
Energy in the form of long waves with low energy.
Energy in the form of short waves with high energy.
Energy propagated through matter and space including long and short waves.

4. What is the maximum amount of ionizing energy used in food processing agreed upon internationally?

5 MeV
10 MeV
15 MeV
20 MeV

5. Enzymes remain active after irradiation unlike the inactivation they undergo during blanching.