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Food irradiation is the process of exposing foodstuffs to a source of energy capable of stripping electrons from individual atoms in the targeted material (ionizing radiation). This ionizing radiation is emitted by a radioactive substance or generated by high-energy accelerators including X-ray converters. Irradiation (in this context "ionizing radiation" is implied) is also used for non-food applications, such as medical devices, plastics, tubes for gas pipelines, hoses for floor heating, shrink-foils for food packaging, automobile parts, wires and cables (isolation), tires, and even gemstones.
As the energetic particles or waves pass through the target material they collide with particles. Around the sites of these collisions chemical bonds are broken. When collisions damage DNA or RNA effective reproduction becomes unlikely, also when collisions occur in cells, cell division is often suppressed. This treatment is used to preserve food, reduce the risk of food borne illness, prevent the spread of invasive pests, delay or eliminate sprouting or ripening, increase juice yield, and improve re-hydration.
Irradiated food does not become radioactive, as the radioactive source is never in contact with the foodstuffs and energy of radiation is limited below the threshold of induction of radioactivity. There is some controversy in the application of irradiation possibly due to it being confused with radioactive contamination or an association with the nuclear industry. Some may also think that chemical changes will be different than the chemical changes due to heating food (as higher energy transfer per collision occurs). However, research has found that this is not a major concern.
Food irradiation is currently permitted by over 50 countries, and the volume of food treated is estimated to exceed 500,000 metric tons annually worldwide; however, the extent of clearances is varying significantly, from a single food category (dried herbs, spices and vegetable seasonings) in Austria, Germany, and many other countries of the European Union to any food in Brazil.
When the irradiating energy collides with the target material electrons are stripped from there atoms, creating short lived radicals (e.g. the Hydroxyl radical, the hydrogen atom and solvated electrons) that damage DNA and cellular structures. This can damage DNA beyond its ability to repair, break down cell membranes, and interrupt enzymic pathways. Because of the inability for cells to divide, the target ceases all processes related to maturation or reproduction.
Depending on the dose, some or all of the microorganisms, bacteria, viruses, or insects present are destroyed or rendered incapable of reproduction, reducing or eliminating the risk of food borne illness. When the enzymic action is slowed down and spoilage organisms are affected spoilage is halted or slowed down. This prolongs the shelf-life and has been shown to delay the ripening of fruits and the sprouting of vegetables. Some foods, e.g., herbs and spices, are irradiated at sufficient doses (five kilograys or more) to reduce the microbial counts by several orders of magnitude; such ingredients do not carry over spoilage or pathogen microorganisms into the final product.
Insect pests are sterilized (be made incapable of proliferation) using irradiation at relatively low doses. This stops the importation of invasive species, and allows foods to pass quickly through quarantine.
Food irradiation is sometimes referred to as "cold pasteurization" or "electronic pasteurization" because ionizing the food does not heat the food to high temperatures during the process, as in heat-pasteurization (at a typical dose of 10 kGy, food that is physically equivalent to water would warm by about 2.5 °C). The treatment of solid food by ionizing radiation can provide an effect similar to heat pasteurization of liquids, such as milk. The use of the term "cold pasteurization" to describe irradiated foods is controversial, because pasteurization and irradiation are fundamentally different processes, although the intended end results can in some cases be similar.
There are other existing practices currently being used that do not involve radiation to reduce pathogens, increase shelf life, eliminate pests, increase juice yield, delay sprouting, and improve re-hydration. Also pathogens in foods could be reduced by more sanitary and stronger regulated agricultural practices. This said these practices can only reduce the risk to a limited degree, where processing by ionizing radiation could practically eliminate these risks.
Because of the risks associated with working with radioactive sources, care must be taken not to expose the operators to radiation, and to contaminate the environment or treated food with radioactive material. During operation of the facility the workers and the environment are shielded from radiation.
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 personal at multiple facilities, and improvements are mandated to retrofit existing facilities and future design.
Electron irradiation uses electrons accelerated in an electric field to a velocity close to the speed of light. Electrons are particulate radiation and, as any other particulate radiation, have a limited range in matter. For this reason, electrons do not penetrate the product beyond a few centimeters, depending on product density.
Electron facilities rely on substantial concrete shields to protect workers and the environment from radiation exposure.
Gamma irradiation involves exposing the target material to highly energetic packets of light (Gamma rays). The sources for this radiation in the processing of food are radioactive materials (radioisotopes). A pallet or tote is typically exposed for several minutes to hours depending on dose.
Radioactive material must be monitored and carefully stored to shield workers and the environment from its gamma rays. With most designs the radioisotope can be lowered into a water-filled source storage pool to allow maintenance personnel to enter the radiation shield. In this mode the water in the pool absorbs the radiation. In some gamma irradiators the radioactive source is under water at all times, and the hermetically sealed (airtight) product is lowered into the water. No further shielding is required for such designs. Other uncommonly used designs feature dry storage by providing movable shields that reduce radiation levels in areas of the irradiation chamber.
Generally cobalt-60 is used as a radioactive source for food irradiation, because the deeper penetration enables administering treatment to entire industrial pallets or totes, reducing the need for material handling. Cobalt-60 is bred from cobalt-59 using neutron irradiation in specifically designed nuclear reactors.
In limited applications caesium-137, a less costly alternative to cobalt-60, is used as a radioactive source. Caesium-137 is recovered during the processing of spent nuclear fuel, therefore insufficient quantities are available for large scale commercial use. An incident in Decatur, Georgia where water soluble caesium-137 leaked into the source storage pool requiring NRC intervention has led to near elimination of this radioisotope outside of military applications.
X-ray irradiators are scalable and have deep penetration comparable to Co-60, with the added benefit that the electronic source stops radiating when switched off. They also permit dose uniformity, but these systems generally have low energetic efficiency during the conversion of electron energy to photon radiation requiring much more electrical energy than other systems.
X-ray facilities rely on substantial concrete shields to protect workers and the environment from radiation exposure.
Nominal X-ray energy is usually limited to 5 MeV; the USA has provisions for up to 7.5 MeV, which increases conversion efficiency. Another development is the availability of electron accelerators with extremely high power output, up to 1,000 kW beam. At a conversion efficiency of up to 12%, the X-ray power may reach (including filtering and other losses) 100 kW; this power would be equivalent to a gamma facility with Co-60 of about 6.5 MCi.
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. 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 (cobalt-60), 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.
Treatment costs vary as a function of dose and facility usage. Low dose applications such as disinfestation of fruit range between US$0.01/lbs and US$0.08/lbs while higher dose applications can cost as much as US$0.20/lbs.
"Dose" (short for radiation absorbed dose) is the physical quantity governing the radiation processing of food, relating to the beneficial effects to be achieved. It is measured in the SI unit known as the gray (Gy). One gray of radiation is equal to 1 joule of energy absorbed per kilogram of food material. In radiation processing of foods, the doses are generally measured in kilograys (kGy, 1,000 Gy).
The measurement of radiation dose is referred to as dosimetry and involves exposing dosimeters jointly with the treated food item. Dosimeters are small components attached to the irradiated product made of materials that, when exposed to ionizing radiation, change specific, measurable physical attributes to a degree that can be correlated to the dose received. Modern dosimeters are made of a range of materials, such as alanine pellets, perspex (PMMA) blocks, and radiochromic films, as well as special solutions and other materials. These dosimeters are used in combination with specialized read out devices. Standards that describe calibration and operation for radiation dosimetry, as well as procedures to relate the measured dose to the effects achieved and to report and document such results, are maintained by the American Society for Testing and Materials (ASTM international) and are also available as ISO/ASTM standards.
On the basis of the dose of radiation the application is generally divided into three main categories:
These doses are above those currently permitted in the USA for commercial food items by the FDA and other regulators around the world. The European Union countries allow dried herbs and spices to be irradiated to a maximum dose of 15 kGy which is equal to an "overall average dose" of 10 kGy as defiend under EU Directives (i.e. at the maximum dose uniformity ratio (maximum dose / minimum dose) of 3 allowed in the EU and using the relationship that "overall average dose" for dried herbs and spices is equal to the average of the sum of the maximum dose and minimum dose). 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.
Irradiation has not been widely adopted due to an asserted negative public perception, the concerns expressed by some consumer groups and the reluctance of many food producers. Consumer perception of foods treated with irradiation is more negative than those processed by other means. "People think the product is radioactive," said Harlan Clemmons, president of Sadex, a food irradiation company based in Sioux City, Iowa.
Consumer organizations, environmentalist groups, and opponents to food irradiation refer to some studies suggesting that a large part of the public questions the safety of irradiated foods, and will not buy foods that have been irradiated (see also circular reasoning).[verification needed]
On the other hand, other studies indicate the number of consumers concerned about the safety of irradiated food has decreased in the last 10 years and continues to be less than the number of those concerned about pesticide residues, microbiological contamination, and other food related concerns. Such numbers are comparable to those of people with no concern about food additives and preservatives. Consumers, given a choice and access to irradiated products, appear ready to buy it in considerably large numbers.
Labeling laws differ from country to country. While Codex Alimentarius represents the global standard in particular under the WTO-agreement, member states are free to convert those standards into national regulations. With regard to labeling of irradiated food, detailed rules are published at CODEX-STAN – 1 (2005) labelling of prepacked food.
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. This definition does not include foods where one of the ingredients is irradiated. This definition is not consistent with the Codex Alimentarius. All irradiated foods must bear the Radura symbol at the point of sale and the term "irradiated" or a derivative there of, in conjunction with explicit language describing the change in the food or its conditions of use.
The meaning of the label is not consistent as the amount of irradiation used can vary and the FDA regulations are on a product by product basis. The amount of pathogens affected by irradiation can vary as well.
Food that is processed as an ingredient by a restaurant or food processor is exempt from the labeling requirement in the US.
The Radura logo as regulated by FDA is slightly different from the international version as proposed in Codex Alimentarius.
The European union follows the Alimentarius provision to label irradiated ingredients down to the last molecule. However, there is no option provided to use the RADURA-logo (what would not exclude to use this logo voluntarily). The European Union is particularly strict in enforcing irradiation labeling 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 in the OJ of the European Communities.
There are analytical methods available to detect the usage of irradiation on food items in the marketplace. This may be understood as a tool for government authorities to enforce existing labeling standards and to bolster consumer confidence.
Currently, there is no global trade in irradiated food, except a rather small quantity of fruit irradiated to eliminate insect pests and to fulfill the US quarantine requirements.
Certain supermarkets prefer not to carry irradiated products for reasons of consumer perception.
Mexico may become the largest exporter of irradiated produce to the U.S. at this point. Varieties will include Mango, Sweet citrus, Manzano Pepper, Starfruit, Guava according to the current US / Mexico irradiation work plan.
Irradiated foods produced within the EU that fall within the single category; 'dried aromatic herbs, spices and vegetable seasonings' are permitted presently in all 27 member states of the European Community. Though imports into the EC are possible from third countries and the seven countries (Belgium, Czech Republic, France, Italy, Netherlands, Poland, United Kingdom) that allow other irradiated foods to be marketed as long as they comply with Directive 1999/2/EC.
The controls on food irradiation, and in particular the strict labeling requirements are regarded by many as restrictive. It is rare to find irradiated and clearly labelled food items on sale. The European Union's official site gives information on the regulatory status of food irradiation, the quantities of foods irradiated at authorized facilities in European Union member states and the results of market surveillance where foods have been tested to see if they are irradiated. The Official Journal of the European Union publishes annual reports on food irradiation, the current report  covers the period from 1 January 2010 to 31 December 2010 and compiles information from 27 Member States.
In total, 9263.4 tonnes of food products were irradiated in European Union countries in 2010; mainly in three member state countries: Belgium (63%), the Netherlands (17%) and France (11%). The three types of foods irradiated the most were frog legs (48%), poultry (23%) and dried herbs and spices (16%).
A series of fatal cat incidents with irradiated pet food in Australia led the cat food company responsible to recall any product from the market. Irradiation at elevated doses or heat sterilization was compulsory at the time of this incident. The company and several scientist speculated this might have been caused by Vitamin A depletion. Over 40 cats were reported to have been euthanized after severe paralysis subsequent to being fed a particular brand of cat food.
Radiation processing of imported cat food has now been banned in Australia. The AQIS announced on June 6, 2009 that the alternative of radiation processing for cat food is no longer acceptable and that irradiated dog food is required to be labeled "Must not be fed to cats".
Since 2009, no study has been published contributing to clearing-up this issue.
Hundreds of animal feeding studies of irradiated food, including multigenerational studies, have been performed since 1950. Endpoints investigated have included subchronic and chronic changes in metabolism, histopathology, and function of most systems; reproductive effects; growth; teratogenicity; and mutagenicity. A large number of studies have been performed; meta-studies have supported the safety of irradiated food.
Processing of food by ionizing radiation causes a multitude of chemical changes. Without these changes there could be no beneficial effects from this process. Such changes are not unique to irradiation, and other common techniques cause changes that are even more extreme. Cooking, smoking, salting, and other less novel techniques, cause the food to be altered so drastically that the final product is changed by its identity and must be called by a different name; in some cases (green beans) cooking removes even a toxic compound. Storage of food induces dramatic chemical changes leading to deterioration and spoilage. Irradiation causes many chemical changes, and from the beginning of research into irradiated food the focus has been on the safety of such changes. The formation of possibly new, hitherto unknown chemical compounds has been a concern. However, research has found that most, if not all, of the substances formed in irradiated food are also found in food that has been subjected to other processing treatments and are not exclusively formed by irradiation. Furthermore, the quantities in which they occur in irradiated food are not significantly higher than those being formed in heat treatments. Up-to-date, there is only a single compound, 2-ACBs, under scrutiny. These results lead to the conclusion that irradiated food in general is safe to consume. Several national expert groups came to the same result; on top of all two international expert groups have in full detail evaluated the available data and finally concluded that any food at any dose is wholesome and safe to consume as long as it remains palatable and maintains its technical properties. In other words, as a steak burned to coal has lost its sensory and meat properties, and any over-irradiated food item will lose all of its desirable properties; the radiation doses to cause toxic changes are much higher than the doses needed to accomplish the benefits of irradiation.
Concerns have been expressed by public interest groups and public health experts that irradiation, as a non-preventive measure, might disguise or otherwise divert attention away from poor working conditions, sanitation, and poor food-handling procedures that lead to contamination in the first place.
Consumer advocacy groups such as Public Citizen or Food and Water Watch maintain that the safety of irradiated food is not proven, in particular long-term studies are still lacking, and strongly oppose the use of the technology.
Concerns and objections include the possibility that food irradiation might do any of the following:
Processors of irradiated food are subject to all existing regulations, inspections, and potential penalties regarding plant safety and sanitation; including fines, recalls, and criminal prosecutions. But critics of the practice claim that a lack of regulatory oversight (such as regular food processing plant inspections) necessitates irradiation.
While food irradiation can in some cases maintain the quality (i.e. general appearance and "inner" quality) of certain perishable food for a longer period of time, it cannot undo spoilage that occurred prior to irradiation. Irradiation cannot successfully be used to mask quality issues other than pathogens. As with heat pasteurization (for example, milk), processing by ionizing radiation can contribute to eliminate pathogen risks from solid food (example meat or lettuce). For comparison, milk heat pasteurization is not being alleged to be a method "to cover up poor food quality"; consequently, food irradiation should not be accused to serve such criminal purposes. Under a HACCP-concept (Hazard Analysis and Critical Control Point) radiation processing can serve and contribute as an ultimate critical control point before the food reaches the consumer.
Opponents of food irradiation and consumer activists argue that the final proof is missing that irradiated food is "safe" (i.e. not unwholesome) and that the lack of long-term studies should be a further reason not to permit food irradiation. Opponents also refer to a number of scientific publications reporting significant negative effects of irradiated food, for example
However, those experiments could be either not verified in later experiments, could not be clearly attributed to the radiation effect, or could be attributed to an inappropriate design of the experiment etc.
The provisions are that any "first generation" product must be labeled "irradiated" as any product derived directly from an irradiated raw material; for ingredients the provision is that even the last molecule of an irradiated ingredient must be listed with the ingredients even in cases where the unirradiated ingredient does not appear on the label. The RADURA-logo is optional; several countries use a graphical version that differs from the Codex-version. There is not much information about irradiated food available to the consumer on the market place; a few more recent surveys do not reveal the full picture. It may be assumed that even international trade exists.
The United Nations Food and Agricultural Organization (FAO) has passed a motion to commit member states to implement irradiation technology for their national phytosanitary programs; the General assembly of the International Atomic Energy Agency (IAEA) has urged wider use of the irradiation technology.
Food irradiation in the United States is primarily regulated by the FDA since it is considered a food additive. Other federal agencies that regulate aspects of food irradiation include:
Each new food is approved separately with a guideline specifying a maximum dosage; in case of quarantine applications the minimum dose is regulated. Packaging materials containing the food processed by irradiation must also undergo approval.
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; the U.S. Food and Drug Administration (FDA) has cleared among a number of other applications the treatment of hamburger patties to eliminate the residual risk of a contamination by a virulent E. coli.
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.
Directives 1999/2/EC (framework Directive) and 1999/3/EC (implementing Directive) regulate the processing of food by the application of ionizing radiation in the European Union, and have been in effect since 1999. These directives do not govern "the irradiation of foodstuffs which are prepared for patients requiring sterile diets under medical supervision" or foodstuffs exposed to ionising radiation generated by most inspection devices. The directives forbid food iradiation for all foodstuffs not in the positive list (found in the ANNEX of the implementing Directive). It also states that iradiation shall not be used "as a substitute for hygiene or health practices or good manufacturing or agricultural practice". The directives and relevant documents and reports are accessible online.
The Scientific Committee on Food (SCF) of the EC had given a positive vote on eight categories of food to be irradiated. However, in a compromise between the European Parliament and the European Commission, only dried aromatic herbs, spices, and vegetable seasonings can be found in the positive list. However, any Member State is permitted to maintain previously granted clearances or to add new clearance as granted in other Member States, in the case the EC's Scientific Committee on Food (SCF) has given a positive vote for the respective application. Presently, seven Member States (Belgium, Czech Republic, France, Italy, Netherlands, Poland, United Kingdom) have adopted such provisions.
The European Commission was due to provide a final draft for the positive list by the end of 2000; however, this failed because of a veto from Germany and a few other Member States. In 1992, and in 1998 the SCF voted "positive" on a number of irradiation applications that had been allowed in some member states before the EC Directives came into force, to enable those member states to maintain their national authorizations.
It is because of the "Single Market" of the EC that 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.
|This article may be confusing or unclear to readers. (September 2013)|
In 2003, the Codex Alimentarius removed any upper dose limit for food irradiation and at the same time stopped using the term "overall average dose" (instead referring to maximum dose and minimum dose), the SCF adopted a "revised opinion", but, in fact, it did not understand that the concept of "overall average dose" had been replaced, and SCF revised opinion was a re-confirmation and endorsement of the 1986 opinion. The opinion denied cancellation of the upper dose limit, and required that before the actual list of individual items or food classes (as in the opinions expressed in 1986, 1992 and 1998) can be expanded, new individual studies into the toxicology of each of such food and for each of the proposed dose ranges are requested. The SCF has subsequently been replaced by the new European Food Safety Authority (EFSA). In April 2011, EFSA’s experts updated their scientific advice on the safety of food irradiation. In its comprehensive advice to EU policy makers, The EFSA BIOHAZ Panel looked at the efficacy and microbiological safety of the process, and the CEF Panel looked at possible risks arising from the formation of chemical substances as a result of food irradiation. A summary of their findings and recommendations, was published, as were two detailed reports; one on the chemical safety, of food irradiation and the other on the efficacy and microbiological safety, of food irradiation.
Such countries as Pakistan and Brazil have adopted the Codex Alimentarius Standard on Irradiated Food without any reservation or restriction: i.e., any food may be irradiated to any dose.
Other countries, including New Zealand, Australia, Thailand, India, and Mexico, have permitted the irradiation of fresh fruits for fruit fly quarantine purposes, amongst others.