From Wikipedia, the free encyclopedia - View original article
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). The radiation can be emitted by a radioactive substance or generated electrically.
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. It is permitted by over 50 countries, with 500,000 metric tons of foodstuffs annually processed worldwide.
Food irradiation is criticized because irradiation can initiate chemical changes that are different than those that occur when heating food (Unique Radiolytic Products). Some people worry that there is the potential of danger from these substances. Research has discovered that one family of chemicals is uniquely formed by irradiation, and this product is nontoxic. When heating food, all other chemicals occur in a lower or comparable frequency. Others criticize irradiation because of confusion with radioactive contamination or because of negative impressions of the nuclear industry.
The regulations that dictate how food is to be irradiated, as well as the food 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.
Irradiation 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.
Irradiation is used to reduce the pathogens in foods. Depending on the dose, some or all of the microorganisms, bacteria (as well as "good bacteria" that inhibit the growth of pathogenic bacteria), and viruses present are destroyed, slowed down, or rendered incapable of reproduction. This reduces or eliminates the risk of food borne illnesses. Some foods are irradiated at sufficient doses to ensure that the product is sterilized and does not add any spoilage or pathogenic microorganisms into the final product.
Irradiation is used to as delay the ripening of fruits and the sprouting of vegetables by slowing down the enzymatic action in foods.
By halting or slowing down spoilage and slowing down the ripening of food, irradiation prolongs the shelf life of goods. Irradiation can not revert spoiled or over ripened food to a fresh state. If this food was processed by irradiation, spoilage would cease and ripening would slow down, yet the irradiation would not destroy the toxins or repair the texture, color, or taste of the food.
Insect pests are sterilized using irradiation at relatively low doses if irradiation. This stops the spread of foreign invasive species across national boundaries, and allows foods to pass quickly through quarantine and avoid spoilage. Depending on the dose, some or all of the insects present are destroyed, or rendered incapable of reproduction.
Irradiation has been approved by the FDA for over 50 years, but the only major growth area for the commercial sale of irradiated foods for human consumption are fruits and vegetables that are irradiated to kill insects for the purpose of quarantine. In the early 2000s in the US irradiated meat was common at some grocery stores, but because of lack of consumer demand it is no longer common. Because consumer demand for irradiated food is low, reducing the spoilage between manufacture and consumer purchase and reducing the risk of food born illness is currently not sufficient incentive for most manufactures to supplement their process with irradiation.
It is widely believed that consumer perception of foods treated with irradiation is more negative than those processed by other means, although some industry studies indicate the number of consumers concerned about the safety of irradiated food has decreased in the last 10 years to levels comparable to those of people concerned about food additives and preservatives. “These irradiated foods are not less safe than others,” Dr. Tarantino said, “and the doses are effective in reducing the level of disease-causing micro-organisms.” "People think the product is radioactive," said Harlan Clemmons, president of Sadex, a food irradiation company based in Sioux City, Iowa.
Some common concerns about food irradiation include the impact of irradiation on food chemistry, as well as the indirect effects of irradiation becoming a prevalent in the food handling process. Irradiation reduces the risk of infection and spoilage, does not make food radioactive, and the food is shown to be safe, but it does cause chemical reactions that alter the food and therefore alters the chemical makeup, nutritional content, and the sensory qualities of the food. The some of the potential secondary impacts of irradiation are hypothetical, while others are demonstrated. These effects include impacts due to the reduction of food quality, the loss of bacteria, and the irradiation process. Because of these concerns and the increased cost of irritated foods, there is not a widespread public demand for the irradiation of foods for human consumption.
The irradiation source supplies energetic particles or waves. As these waves/particles pass through a target material they collide with particles. Around the sites of these collisions chemical bonds are broken, 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 striping particles from nearby molecules. When collisions damage DNA or RNA, effective reproduction becomes unlikely, also when collisions occur in cells, cell division is often suppressed.
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, but it does reduce the nutritional content and change the flavor (much like cooking), produce radiolytic products, and increase the number of free radicals in the food.
Irradiation causes a multitude of chemical changes. The scale of these chemical changes caused by irradiation are not unique. Cooking, smoking, salting, and other less novel techniques, cause the food to be altered so drastically that its original nature is almost unrecognizable, and must be called by a different name. Storage of food also causes dramatic chemical changes, ones that eventually lead to deterioration and spoilage.
Because of the extent of the chemical reactions, changes to the foods quality after irradiation are inevitable. The nutritional content of food, as well as the sensory qualities (taste, appearance, and texture) are impacted by irradiation. Because of this food advocacy groups consider labeling irradiated food raw as misleading.
The changes in quality and nutrition vary greatly from food to food. The changes in the flavor of fatty foods like meats, nuts and oils are sometimes noticeable, while the changes in lean products like fruits and vegetables are less so. Some studies by the irradiation industry show that for some properly treated fruits and vegetables irradiation is seen by consumers to improve the sensory qualities of the product compared to untreated fruits and vegetables.
The formation of new, previously unknown chemical compounds (Unique Radiolytic Products) via irradiation is a concern. Research has shown that most of the substances found in irradiated food are also found in food that has been subjected to other food processing treatments, and are therefore not unique. Furthermore, the quantities in which they occur in irradiated food are lower or similar to the quantities formed in heat treatments.
When fatty acids are irradiated, a family of compounds called 2-alkylcyclobutanones (2-ACBs) are produced. These are thought to be unique radiolytic products. Some studies show that these chemicals may be toxic, while others dispute this.
Potentially damaging compounds known as free radicals form when food is irradiated. Most of these are oxidizers (i.e., accept electrons) and some react very strongly. According to the free-radical theory of aging excessive amounts of these free radicals can lead to cell injury and cell death, which may contribute to many diseases.
The radiation doses to cause toxic changes are much higher than the doses needed to accomplish the benefits of irradiation, and taking into account the presence of 2-ABCs along with what is known of free radicals, these results lead to the conclusion that there is no significant risk from radiolytic products.
Several national expert groups and two international expert groups evaluated the available data and concluded that any food at any dose is wholesome and safe to consume as long as it remains palatable and maintains its technical properties (e.g. feel, texture, or color). Still, a major concern is that irradiation might cause chemical changes that are harmful to the consumer. In particular the argument is that there is a lack of long-term studies, and therefore the safety of irradiated food is not scientifically proven in spite of the fact that 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.
The below experiments are cited by food irradiation opponents[weasel words], but 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.
A series of deaths in cats fed a particular brand of irradiated cat food in Australia led the manufacturer to recall the product from the market. However, evidence indicates the problem was specific to the lot and was not related to the irradiation process because:
Radiation processing of imported cat food has now been banned in Australia. The AQIS announced on June 6, 2009 that 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".
Many of the concerns and benefits of irradiation are not directly related to the chemical changes that occur when food is irradiated, but instead are related to what would occur if food irradiation was a common process. When food is irradiated some nutrition is lost. Therefore, if the majority of food was irradiated at high enough levels to decrease its nutritional content significantly, there could be an increase in nutritional deficiencies due to a diet composed entirely of irradiated foods.
If irradiation was to become common in the food handling process there would be a reduction of the prevalence of foodborne illness and potentially the eradication of specific pathogens. Multiple studies support that an increased rate of pathogen growth may occur when irradiated food is cross-contaminated with a pathogen, as the competing spoilage organisms are no longer present. This would seem to contradict the assertion there would be a reduction of the prevalence of foodborne illness, but this impact would be outweighed by the decrease of illness due to a non cross contaminated source, and the decrease in the possibility of cross contamination.
The ability to remove bacterial contamination through post-processing by irradiation may reduce the fear of mishandling food which could cultivate a cavalier attitude toward hygiene and result in contaminants other than bacteria. Concerns that the pasteurization of milk would lead to increased contamination of milk where prevalent when mandatory pasteurization was introduced. These fears never materialized after adoption of this law. Therefore, it is unlikely for irradiation to cause an increase of illness due to non bacteria based contamination.
If irradiation becomes a standard process there are concerns that irradiating food might create dangerous or radiation tolerant pathogens. Repeatedly processing the same product with of irradiation have been shown to produce irradiation tolerant bacteria. Because of this some are worried that pathogens will develop resistance to irradiation the way that strains of bacteria have developed resistance to antibiotics. Products that pass through irradiation plants are processed once, and are not processed and reprocessed, much like pasteurization plants. Cycles of heat treatment have been shown to produce heat tolerant bacteria, yet no problems have appeared so far in pasteurization plants. Furthermore, when the irradiation dose is chosen to target a specific species of microbe, it is calibrated to doses doses several times the value required to target the species. This ensures that the process can destroy all members of a target species making the process random with respect to irradiation tolerance for this target species. Therefore, irradiation does not encourage the growth of irradiation tolerant bacteria in the target species.
Up to the point where the food is processed by irradiation, the food is processed in the same way as all other food. To treat the foodstuffs, they are exposed to a radioactive source, for a set period of time to achieve a desired dose. Radiation may be emitted by a radioactive substance, or by X-ray and electron beam accelerators. Special precautions are taken to ensure the food stuffs never come in contact with the radioactive substances and that the personnel and the environment are protected from exposure radiation.
Irradiation treatments are typically classified by dose (high, medium, and low), but are sometimes classified by the effects of the treatment (radappertization, radicidation and radurization). 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, and the effect is similar to heat pasteurization. The term "cold pasteurization" is controversial because the term may be used to disguise the fact the food has been irradiated and pasteurization and irradiation are fundamentally different processes.
Treatment costs vary as a function of dose and facility usage. A pallet or tote is typically exposed for several minutes to hours depending on dose. 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.
|This section needs additional citations for verification. (June 2014)|
Typically, when the food is being irradiated, pallets of food are exposed a source of radiation for a specific time. Dosimeters are embedded in the pallet (at various locations) of food to determine what dose was achieved.
Most irradiated food is processed by gamma irradiation. Special precautions are taken because gamma rays are continuously emitted by the radioactive material. In most designs, to nullify the effects of radiation, the radioisotope is lowered into a water-filled storage pool, which absorbs the radiation but does not become radioactive. This allows pallets of the products to be added and removed from the irradiation chamber and other maintenance to be done. Sometimes movable shields are used to reduce radiation levels in areas of the irradiation chamber instead of submerging the source. For x ray and electron irradiation these precautions are not necessary as the source of the radiation can be turned off.
For x-ray, gamma ray and electron irradiation, shielding is required when the foodstuffs are being irradiated. This is done to protect workers and the environment outside of the chamber from radiation exposure. Typically permanent or movable shields are used. In some gamma irradiators the radioactive source is under water at all times, and the hermetically sealed product is lowered into the water. The water acts as the shield in this application. Because of the lower penetration depth of electron irradiation, treatment to entire industrial pallets or totes is not possible.
The radiation absorbed dose is the amount energy absorbed per unit weight of the target material. Dose is used because, when the same substance is given the same dose, similar changes are observed in the target material. The SI unit for dose is grays (Gy or J/kg). Dosimeters are used to measure dose, and are small components that, when exposed to ionizing radiation, change measurable physical attributes to a degree that can be correlated to the dose received. Measuring dose (dosimetry) involves exposing one or more dosimeters along with the target material.
Doses are generally divided into low (up to 1 kGy), medium (1 kGy to 10 kGy), and high dose applications (above 10 kGy). High dose applications are above those currently permitted in the USA for commercial food items by the FDA and other regulators around the world. 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.
|Low dose (up to 1 kGy)||Medium dose (1 kGy to 10 kGy)||High dose (above 10 kGy)|
|Application||Dose (kGy)||Application||Dose (kGy)||Application||Dose (kGy)|
|Inhibit sprouting[a]||0.03-0.15 kGy||Delay spoilage of meat[b]||1.50–3.00 kGy||Sterilization[c] of packaged meat[b]||25.00-70.00 kGy|
|Delay fruit ripening||0.03-0.15 kGy||Reduce risk of pathogens in meat[b]||3.00–7.00 kGy||Increase juice yield|
|Stop insect/parasite infestations[d]||0.07-1.00 kGy||Increase sanitation[e] of spices||10.00 kGy||Improve re-hydration|
Electron irradiation uses electrons accelerated in an electric field to a velocity close to the speed of light. Electrons are particles, and therefore do not penetrate the product beyond a few centimeters, depending on product density.
Gamma irradiation involves exposing the target material to packets of light (photons) that are highly energetic (Gamma rays). A radioactive material (radioisotopes) is used as the source for the gamma rays. Gamma irradiation is the standard because the deeper penetration of the gamma rays enables administering treatment to entire industrial pallets or totes (reducing the need for material handling) and it is significantly less expensive than using a X-ray source. Generally cobalt-60 is used as a radioactive source for gamma irradiation. Cobalt-60 is bred from cobalt-59 using neutron irradiation in specifically designed nuclear reactors. In limited applications caesium-137, a less costly alternative recovered during the processing of spent nuclear fuel, is used as a radioactive source. Insufficient quantities are available for large scale commercial use. An incident 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.
Irradiation by X-ray is similar to irradiation by gamma rays in that less energetic packets of light (X-rays) are used. X-rays are generated by colliding accelerated electrons with a dense material (this process is known as bremsstrahlung-conversion), and therefore do not necessitate the use of radioactive materials. X-rays ability to penetrate the target is similar to gamma irradiation. X-ray machine produces better dose uniformity then Gamma irradiation but they require much more electricity as only as much as 12% of the input energy is converted into X-rays.
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, 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.
The Codex Alimentarius represents the global standard for irradiation of food, in particular under the WTO-agreement. Member states are free to convert those standards into national regulations at there discretion. Therefore regulations about irradiation differ from country to country.
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.
The provisions of the Codex Alimentarius 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. The suggested rules for labeling prepacked is published at CODEX-STAN – 1 (2005), 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 foodstuffs. The European Community 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 in the OJ of the European Communities.
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. This definition is not consistent with the Codex Alimentarius. All irradiated foods must bear a slightly modified Radura symbol at the point of sale and use the term "irradiated" or a derivative there of, in conjunction with explicit language describing the change in the food or its conditions of use.
In 2003, the Codex Alimentarius removed any upper dose limit for food irradiation as well as clearances for specific foods, declaring that all are safe to irradiate. Countries such as Pakistan and Brazil have adopted the Codex without any reservation or restriction. Other countries, including New Zealand, Australia, Thailand, India, and Mexico, have permitted the irradiation of fresh fruits for fruit fly quarantine purposes, amongst others.
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.
All of the rules involved in processing foodstuffs are applied to all foods before they are irradiated.
In the United States 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. Food irradiation in the United States is primarily regulated by the FDA since it is considered a food additive. 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 (FDA) and the USDA have approved irradiation of the following foods and purposes:
European law dictates that no foods other than dried aromatic herbs, spices and vegetable seasonings are permitted for the application of irradiation. However, any Member State is permitted to maintain previous clearances that are in categories that the EC's Scientific Committee on Food (SCF) had previously approved, or add clearance granted to other Member States. Presently, Belgium, Czech Republic, France, Italy, Netherlands, Poland, and the United Kingdom) have adopted such provisions. 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 regulations only govern food irradiation in consumer products to allow irradiation to be used for patients requiring sterile diets.
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.
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.
There are analytical methods available to detect the usage of irradiation on food items in the marketplace. This is used as a tool for government authorities to enforce existing labeling standards and to bolster consumer confidence. Phytosanitary irradiation of fruits and vegetables has been increasing globally. In 2010, 18446 tonnes of fruits and vegetables were irradiated in six countries for export quarantine control; the countries follow: Mexico (56.2%), United States (31.2%), Thailand (5.18%), Vietnam (4.63%), Australia (2.69%), and India (0.05%). The three types of fruits irradiated the most were guava (49.7%), sweet potato(29.3%) and sweet lime (3.27%).
In total, 103 000 tonnes of food products were irradiated on mainland United States in 2010. The three types of foods irradiated the most were spices (77.7%), fruits and vegetables (14.6%) and meat and poultry (7.77%). 17 953 tonnes of irradiated fruits and vegetables were exported to the mainland United States. Mexico, the United States' state of Hawaii, Thailand, Vietnam and India export irradiated produce to the mainland U.S. Mexico, followed by the United States' state of Hawaii, is the largest exporter of irradiated produce to the mainland U.S.
In total, 7 972 tonnes of food products were irradiated in European Union countries in 2012; mainly in three member state countries: Belgium (64.7%), the Netherlands (18.5%) and France (7.7%). The three types of foods irradiated the most were frog legs (36%), poultry (35%) and dried herbs and spices (15%). 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 2012 to 31 December 2012 and compiles information from 27 Member States.
|last1=in Authors list (help)
|Wikimedia Commons has media related to Food irradiation.|
|Wikibooks has more on the topic of: Food irradiation|
|Look up food irradiation in Wiktionary, the free dictionary.|