Food irradiation

thumb|150px|right|The international [[Radura logo, used to show a food has been treated with ionizing radiation.]]

thumb|A portable, trailer-mounted food irradiation machine,

Food irradiation (sometimes called radurization in American English, and radurisation in British English) is the process of exposing food and food packaging to ionizing radiation, such as from gamma rays, x-rays, or electron beams. Food irradiation improves food safety and extends product shelf life (preservation) by effectively destroying organisms responsible for spoilage and foodborne illness, inhibits sprouting or ripening, and is a means of controlling insects and invasive pests. The U.S. Food and Drug Administration (FDA), the World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), and U.S. Department of Agriculture (USDA) have performed studies that confirm irradiation to be safe.

Food irradiation is permitted in over 60 countries, and about 500,000 metric tons of food are processed annually worldwide. The regulations for how food is to be irradiated, as well as the foods allowed to be irradiated, vary greatly from country to country. In Austria, Germany, and many other countries of the European Union only dried herbs, spices, and seasonings can be processed with irradiation and only at a specific dose, while in Brazil all foods are allowed at any dose.

Uses

Irradiation is used to reduce or eliminate pests and the risk of food-borne illnesses as well as prevent or slow spoilage and plant maturation or sprouting. Depending on the dose, some or all of the organisms, microorganisms, bacteria, and viruses present are destroyed, slowed, or rendered incapable of reproduction. When targeting bacteria, most foods are irradiated to significantly reduce the number of active microbes, not to sterilize all microbes in the product. Irradiation cannot return spoiled or over-ripe food to a fresh state. If this food was processed by irradiation, further spoilage would cease and ripening would slow, yet the irradiation would not destroy the toxins or repair the texture, color, or taste of the food.

Irradiation slows the speed at which enzymes change the food. By reducing or removing spoilage organisms and slowing ripening and sprouting (e.g. potato, onion, and garlic) irradiation is used to reduce the amount of food that goes bad between harvest and final use.

Pests such as insects have been transported to new habitats through the trade in fresh produce and significantly affected agricultural production and the environment once they established themselves. To reduce this threat and enable trade across quarantine boundaries, food is irradiated using a technique called phytosanitary irradiation. Phytosanitary irradiation sterilizes the pests preventing breeding by treating the produce with low doses of irradiation (less than 1000 Gy). The higher doses required to destroy pests are not used due to either affecting the look or taste, or cannot be tolerated by fresh produce.

Process

200px|thumbnail|Efficiency illustration of the different radiation technologies (electron beam, X-ray, gamma rays)

The target material is exposed an external source of radiation. The radiation source supplies energetic particles or electromagnetic waves. These particles or waves collide with material in the target. The higher the likelihood of these collisions over a distance are, the lower the penetration depth of the irradiation process is as the energy is more quickly depleted.

These collisions break chemical bonds, creating short lived radicals (e.g. the hydroxyl radical, the hydrogen atom and solvated electrons). These radicals cause further chemical changes by bonding with and or stripping particles from nearby molecules. When collisions occur in cells, cell division is often suppressed, halting or slowing the processes that cause the food to mature.

When the process damages DNA or RNA, effective reproduction becomes unlikely halting the population growth of viruses and organisms.

Not radioactive

Irradiated food does not become radioactive; only particle energies that are incapable of causing significant induced radioactivity are used for food irradiation. In the United States this limit is 4 mega electron volts (MEV) for electron beams and x-ray sources—cobalt-60 or caesium-137 sources are never energetic enough to induce radioactivity. Particles below this energy can never be energetic enough to modify the nucleus of the targeted atom in the food, regardless of how many particles hit the target material, and so radioactivity can not be induced.

For purposes of legislation doses are divided into low (up to 1 kGy), medium (1 kGy to 10 kGy), and high-dose applications (above 10 kGy). though these doses are approved for non commercial applications, such as sterilizing frozen meat for NASA astronauts (doses of 44 kGy) and food for hospital patients.

The ratio of the maximum dose permitted at the outer edge (D<sub>max</sub>) to the minimum limit to achieve processing conditions (D<sub>min</sub>) determines the uniformity of dose distribution. This ratio determines how uniform the irradiation process is.

{| class="wikitable"

|+Applications of food irradiation

|Application

|Dose (kGy)

| rowspan="4" |Low dose (up to 1 kGy)

|Inhibit sprouting (potatoes, onions, yams, garlic)

|0.06 - 0.2

|Delay in ripening (strawberries, potatoes)

|0.5 - 1.0

|Prevent insect infestation (grains, cereals, coffee beans, spices, dried nuts, dried fruits, dried fish, mangoes, papayas)

|0.15 - 1.0

|Parasite control and inactivation (tape worm, trichina)

|0.3 - 1.0

| rowspan="4" |Medium dose (1 kGy to 10 kGy)

|Extend shelf-life of raw and fresh fish, seafood, fresh produce

|1.0 - 5.5

|Extend shelf-life of refrigerated and frozen meat products

|4.5 - 7.0

|Reduce risk of pathogenic and spoilage microbes (meat, seafood, spices, and poultry)

|1.0 - 7.0

|Increased juice yield, reduction in cooking time of dried vegetables

|3.0 - 7.0

| rowspan="4" |High dose (above 10 kGy)

|Enzymes (dehydrated)

|10.0

|Sterilization of spices, dry vegetable seasonings

|30.0 max

|Sterilization of packaging material

|10.0 - 25.0

|Sterilization of foods (NASA and hospitals)

|44.0

Chemical changes

As ionising radiation passes through food, it creates a trail of chemical transformations due to radiolysis effects. Irradiation does not make foods radioactive, change food chemistry, compromise nutrient contents, or change the taste, texture, or appearance of food.

Food quality

Decontamination of food by ionizing radiation is a safe and efficient process for elimination of pathogenic bacteria. Ionizing radiation treatment can be applied to either raw materials or ready to eat foods, with some countries, like the United States, imposing limitations on its use.

Assessed rigorously over several decades, irradiation in commercial amounts to treat food has no negative impact on the sensory qualities and nutrient content of foods. It is traditionally used on horticultural products to prevent sprouting and post-packaging contamination, delay post-harvest ripening, maturation and senescence.

Public perceptions

Some who advocate against food irradiation argue the long-term health effects and safety of irradiated food cannot be scientifically proven, however there have been hundreds of animal feeding studies of irradiated food performed since 1950. Endpoints include subchronic and chronic changes in metabolism, histopathology, function of most organs, reproductive effects, growth, teratogenicity, and mutagenicity.

Industrial process

Up to the point where the food is processed by irradiation, the food is processed in the same way as all other food.

Packaging

For some forms of treatment, packaging is used to ensure the food stuffs never come in contact with radioactive substances and prevent re-contamination of the final product. (radappertisation, radicidation and radurisation). Food irradiation is sometimes referred to as "cold pasteurisation" or "electronic pasteurisation" because ionising the food does not heat it to high temperatures during the process, and the effect is similar to pasteurisation. The term "cold pasteurisation" is controversial because the term may be used to disguise the fact that the food has been irradiated, and pasteurisation and irradiation are fundamentally different processes.

Gamma irradiation

Gamma irradiation is produced from the radioisotopes cobalt-60 and caesium-137, which are produced by neutron irradiation of cobalt-59 (the only stable isotope of cobalt) and as a nuclear fission product, respectively. The special trucks must meet high safety standards and pass extensive tests to be approved to ship radiation sources. Conversely, caesium-137 is water-soluble and poses a risk of environmental contamination. Insufficient quantities are available for large-scale commercial use as the vast majority of Caesium-137 produced in nuclear reactors is not extracted from spent nuclear fuel. An incident where water-soluble caesium-137 leaked into the source storage pool requiring NRC intervention has led to near elimination of this radioisotope.

thumb|Cobalt-60 stored in Gamma Irradiation machine

Gamma irradiation is widely used due to its high penetration depth and dose uniformity, allowing for large-scale applications with high throughput.

Electron beam

Treatment of electron beams is created as a result of high energy electrons in an accelerator that generates electrons accelerated to 99% the speed of light.

X-ray

X-rays are produced by bombardment of dense target material with high-energy accelerated electrons (this process is known as bremsstrahlung-conversion), giving rise to a continuous energy spectrum. Like electron beams, X-rays do not require the use of radioactive materials and can be turned off when not in use. X-rays have high penetration depths and high dose uniformity but they are a very expensive source of irradiation as only 8% of the incident energy is converted into X-rays.

Cost

Irradiation is a capital-intensive technology requiring a substantial initial investment, ranging from $1 million to $5 million. In the case of large research or contract irradiation facilities, major capital costs include a radiation source, hardware (irradiator, totes and conveyors, control systems, and other auxiliary equipment), land (1 to 1.5 acres), radiation shield, and warehouse. Operating costs include salaries (for fixed and variable labor), utilities, maintenance, taxes/insurance, cobalt-60 replenishment, general utilities, and miscellaneous operating costs. Perishable food items, like fruits, vegetables and meats would still require to be handled in the cold chain, so all other supply chain costs remain the same. Food manufacturers have not embraced food irradiation because the market does not support the increased price of irradiated foods, and because of potential consumer backlash due to irradiated foods.

The cost of food irradiation is influenced by dose requirements, the food's tolerance of radiation, handling conditions, i.e., packaging and stacking requirements, construction costs, financing arrangements, and other variables particular to the situation.

State of the industry

Irradiation has been approved by many countries. For example, in the U.S. and Canada, food irradiation has existed for decades.

Although there are some consumers who choose not to purchase irradiated food, a sufficient market has existed for retailers to have continuously stocked irradiated products for years. When labelled irradiated food is offered for retail sale, consumers buy and re-purchase it, indicating a market for irradiated foods, although there is a continuing need for consumer education.

Radurisation risks

The following risks can be mentioned:

As with any sterilisation method, a very small proportion of germs may survive the process, and cause a fraction of the irradiated products to spoil anyway. The risk comes from the false sense of security.
As mentioned above, the treatment only preserves the freshness of the product at the moment it reaches the factory. If it has already lost some of its qualities, this will not be restored, and may even be hidden by the packaging.
While the purpose of the irradiation is to degrade the DNA/RNA of contaminating germs, a small proportion of the nutrient load is also degraded in the process. In particular, vitamins, whole proteins and aromatic molecules.
The irradiation creates highly reactive radicals, which would cause problems if the food is consumed immediately after being irradiated.

Standards and regulations

The Codex Alimentarius represents the global standard for irradiation of food, in particular under the WTO-agreement. Regardless of treatment source, all processing facilities must adhere to safety standards set by the International Atomic Energy Agency (IAEA), Codex Code of Practice for the Radiation Processing of Food, Nuclear Regulatory Commission (NRC), and the International Organization for Standardization (ISO). More specifically, ISO 14470 and ISO 9001 provide in-depth information regarding safety in irradiation facilities. and includes the usage of the Radura symbol for all products that contain irradiated foods. The Radura symbol is not a designator of quality. The amount of pathogens remaining is based upon dose and the original content and the dose applied can vary on a product by product basis.

The European Union follows the Codex's provision to label irradiated ingredients down to the last molecule of irradiated food. The European Union does not provide for the use of the Radura logo and relies exclusively on labeling by the appropriate phrases in the respective languages of the Member States. The European Union enforces its irradiation labeling laws by requiring its member countries to perform tests on a cross section of food items in the market-place and to report to the European Commission. The results are published annually on EUR-Lex.

The US defines irradiated foods as foods in which the irradiation causes a material change in the food, or a material change in the consequences that may result from the use of the food. Therefore, food that is processed as an ingredient by a restaurant or food processor is exempt from the labeling requirement in the US. All irradiated foods must include a prominent Radura symbol followed in addition to the statement "treated with irradiation" or "treated by irradiation.

Approved materials by FDA for Irradiation according to 21 CFR 179.45:

All of the rules involved in processing food are applied to all foods before they are irradiated.

United States

The U.S. Food and Drug Administration (FDA) is the agency responsible for regulation of radiation sources in the United States. Packaging materials containing the food processed by irradiation must also undergo approval. The United States Department of Agriculture (USDA) amends these rules for use with meat, poultry, and fresh fruit.

The United States Department of Agriculture (USDA) has approved the use of low-level irradiation as an alternative treatment to pesticides for fruits and vegetables that are considered hosts to a number of insect pests, including fruit flies and seed weevils. Under bilateral agreements that allows less-developed countries to earn income through food exports agreements are made to allow them to irradiate fruits and vegetables at low doses to kill insects, so that the food can avoid quarantine.

The U.S. Food and Drug Administration and the U.S. Department of Agriculture have approved irradiation of the following foods and purposes:

Packaged refrigerated or frozen red meat — to control pathogens (E. Coli O157:H7 and Salmonella) and to extend shelf life
Packaged poultry — control pathogens (Salmonella and Camplylobacter) — to control insects and microorganisms
Crustaceans (lobster, shrimp, and crab) However, these Directives allow Member States to maintain previous clearances food categories the EC's Scientific Committee on Food (SCF) had previously approved (the approval body is now the European Food Safety Authority). Presently, Belgium, Czech Republic, France, Italy, Netherlands, and Poland allow the sale of many different types of irradiated foods. Before individual items in an approved class can be added to the approved list, studies into the toxicology of each of such food and for each of the proposed dose ranges are requested. It also states that irradiation shall not be used "as a substitute for hygiene or health practices or good manufacturing or agricultural practice". These Directives only control food irradiation for food retail and their conditions and controls are not applicable to the irradiation of food for patients requiring sterile diets. In 2021 the most common food items irradiated were frog legs at 65.1%, poultry 20.6% and dried aromatic herbs, spices and vegetables seasoning.

Due to the European Single Market, any food, even if irradiated, must be allowed to be marketed in any other member state even if a general ban of food irradiation prevails, under the condition that the food has been irradiated legally in the state of origin.

Furthermore, imports into the EC are possible from third countries if the irradiation facility had been inspected and approved by the EC and the treatment is legal within the EC or some Member state.

Australia

In Australia, following cat deaths after irradiated cat food consumption and producer's voluntary recall, cat food irradiation was banned.

Nuclear safety and security

Interlocks and safeguards are mandated to minimize this risk. There have been radiation-related accidents, deaths, and injury at such facilities, many of them caused by operators overriding the safety related interlocks. In a radiation processing facility, radiation specific concerns are supervised by special authorities, while "Ordinary" occupational safety regulations are handled much like other businesses.

The safety of irradiation facilities is regulated by the United Nations International Atomic Energy Agency and monitored by the different national Nuclear Regulatory Commissions. The regulators enforce a safety culture that mandates that all incidents that occur are documented and thoroughly analyzed to determine the cause and improvement potential. Such incidents are studied by personnel at multiple facilities, and improvements are mandated to retrofit existing facilities and future design.

In the US the Nuclear Regulatory Commission (NRC) regulates the safety of the processing facility, and the United States Department of Transportation (DOT) regulates the safe transport of the radioactive sources.

Origin of the word "Radurisation"

The word "radurisation" is derived from radura, combining the initial letters of the word "radiation" with the stem of "durus", the Latin word for hard, lasting.

Historical timeline

1895 Wilhelm Conrad Röntgen discovers X-rays ("bremsstrahlung", from German for radiation produced by deceleration)
1896 Antoine Henri Becquerel discovers natural radioactivity; Minck proposes the therapeutic use
1904 Samuel Prescott describes the bactericide effects Massachusetts Institute of Technology (MIT)
1906 Appleby & Banks: UK patent to use radioactive isotopes to irradiate particulate food in a flowing bed
1918 Gillett: U.S. Patent to use X-rays for the preservation of food
1921 Schwartz describes the elimination of Trichinella from food
1930 Wuest: French patent on food irradiation
1943 MIT becomes active in the field of food preservation for the U.S. Army
1951 U.S. Atomic Energy Commission begins to co-ordinate national research activities
1958 World first commercial food irradiation (spices) at Stuttgart, Germany
1963 FDA approves food irradiation. NASA begins irradiating astronaut food items to prevent food borne illness during space missions.
1970 Establishment of the International Food Irradiation Project (IFIP), headquarters at the Federal Research Centre for Food Preservation, Karlsruhe, Germany
1980 FAO/IAEA/WHO Joint Expert Committee on Food Irradiation recommends the clearance generally up to 10 kGy "overall average dose"
1994 India approves irradiation of spices, potato and onion.
1997 FAO/IAEA/WHO Joint Study Group on High-Dose Irradiation recommends to lift any upper dose limit
1999 The European Union adopts Directives 1999/2/EC (framework Directive) and 1999/3/EC (implementing Directive) limiting irradiation a positive list whose sole content is one of the eight categories approved by the SCF, but allowing the individual states to give clearances for any food previously approved by the SCF.
2000 Germany leads a veto on a measure to provide a final draft for the positive list.
2003 Codex Alimentarius General Standard for Irradiated Foods: no longer any upper dose limit
2003 The SCF adopts a "revised opinion" that recommends against the cancellation of the upper dose limit.
2004 ICGFI ends
2011 The successor to the SCF, European Food Safety Authority (EFSA), reexamines the SCF's list and makes further recommendations for inclusion.

References

External links

Codex Alimentarius
Codex Alimentarius Recommended International Code of Practice Code for Radiation Processing of Foods (CAC/RCP 19-1979, rev.2 – 2003)
General Standard for the Labelling of Prepacked Foods (CODEX STAN 1-1985)
Food Irradiation Processing Alliance FIPA represents the irradiation service industry, manufacturers of food irradiators and suppliers of cobalt-60 sources.
, Center for Food Safety and Applied Nutrition (US Government)
, a series of 14 fact sheets, International Consultative Group on Food Irradiation, International Atomic Energy Agency, Vienna, 1991
Bibliography on Food Irradiation , Federal Research Centre for Nutrition and Food, Karlsruhe, Germany
IAEA interactive map of irradiation facilities