Food Irradiation Technical Summary
Food irradiation is a processing method used to reduce microbial load, retard ripening and control insect infestation by exposing foods to ionizing radiation in the form of electron beams (e-beams), gamma rays or X-rays. The rays penetrate food causing DNA fragmentation in any microbes and insects that are present. This kills the organisms or eliminates their reproductive ability. The process enhances the microbial safety and viability of the treated product. Ripening and sprouting in fruits and vegetables are impeded due to DNA disruption, useful in prolonging shelf life.
Irradiation is also known as cold pasteurization, as it does not impose thermal treatment. Consequently, the process is particularly suitable for raw and frozen foods. Irradiation can be applied to liquid, solid and semi-solid foods. This technology is supported by decades of research studies, including long-term animal feeding studies indicating irradiated foods are safe for human consumption.
The process eliminates microbes and/or insects more effectively than the often-used chemical additives and surface treatments. Vitamin losses such as thiamin and vitamins C, E and K can occur; these nutritional losses are similar to those occurring in food processed by canning, heat pasteurizing or cooking. Within the recommended radiation dose range, nutritional value remains insignificantly compromised. Irradiation can yield safer products than, but superficially indistinguishable from, their non-irradiated counterparts. To attain this, certain parameters, such as processing temperatures, packaging, additives and storage conditions are optimized in conjunction with the correct radiation dose.
Levanduski & Jaczynski (2008) reported that radiation-resistant strains of E.coli O157:H7 were produced by repetitive e-beam exposure at sub-lethal doses, compliant with previously displayed adaptive abilities to stressors such as antibiotics.
Some products are irradiated after packaging to minimize the risk of post-processing contamination. However, when exposed to the treatment, packaging materials can undergo polymerization and/or degradation, which compromises package integrity, and product safety and quality. Radiolysis products may also be generated. Different materials react with varying degrees during the irradiation process, where some are radiation-stable. Pre-market safety assessments are performed for proposed packaging materials for direct product contact during the irradiation process to ensure the absence of significant physical and chemical changes.
International regulations of irradiated foods are circulated by the Codex Alimentarius Commission in the General Standard for Irradiated Foods. Permitted sources of radiation are gamma rays from cobalt-60 or caesium-136 (found in the environment), X-rays (less than < 5 mega electron volt or MeV) or electron beams (less than <10 MeV) (electronically generated). The maximum absorbed dose allowed for commercial foods is 10 kilograys (kGy), where 1 gray is equal to 1 joule of radiant energy absorbed by 1 kilogram of matter. The regulations mandate the possession of a license, the need for qualified personnel for all food irradiation facilities and specify the data recording requirements for tracking and ensuring compliance. These regulations ensure the safety and effectiveness of the irradiation process world-wide.
In Canada, irradiation of food is regulated by Health Canada, as outlined in Division 26 of theFood and Drug Regulations. Irradiation is permitted for potatoes and onions to inhibit sprouting during storage; for wheat, flour and whole wheat flour to control insect infestation during storage; and for whole or ground spices and dehydrated seasoning preparations to reduce the number of microorganisms. Currently, the technology is used mainly on spices.
In 2002, Health Canada completed a scientific review on the use of irradiation for ground beef, fresh and frozen poultry, shrimp and prawns to control pathogens, reduce microbial population and extend durable shelf life. The review also included irradiation of mangoes to control fruit flies and mango seed weevil. Following this review, proposed amendments to the regulations were opened to stakeholders and public comments, and have yet to be incorporated into Canadian regulations. Regulatory approval of irradiation is associated with expensive scientific reviews, and consumer and stakeholder approvals.
The U.S. Food and Drug Administration has approved irradiation for microbial control in raw meat products, dehydrated spices and enzyme preparations, poultry, eggs, seeds for sprouting and shellfish; fresh iceberg lettuce and fresh spinach were added to the list in 2008. The dose required for insect disinfestations is much lower than that for microbial control; the irradiation treatment for this purpose is permitted in the U.S. for all foods. Absorbed dosages exceeding 10 kGy are applied to frozen, packaged meat, which is specifically for use by the National Aeronautics and Space Administration (NASA).
There are concerns about the potential toxicity of irradiation by-products, such as cholesterol oxides and radiolytic products, particularly 2-dodecylcyclobutanones. Research studies have not proven any mutagenic or toxic effects of these compounds when irradiated products are incorporated into a normal diet. It is generally agreed that concentrations of 2-dodecylcyclobutanones required for detrimental effects are much higher than those found in irradiated foods.
Consumer reception of irradiated foods has improved world-wide. There are some concerns that irradiation may be misused as a substitute for good manufacturing practices (GMPs) and sanitation procedures. There are also concerns about the safety surrounding the containment of the irradiation source.
All irradiated whole food products are labeled with the international radiation symbol: a green circle with a plant in the centre, known as the ‘radura’. Prepared foods that contain any irradiated ingredient that makes up more than 10% of the product must have that ingredient labelled as irradiated.
Although food safety and environmental concerns may be addressed with good manufacturing practices and good irradiation practices, some consumers do not want products that have been irradiated. Due to Canadian labelling regulations, one must buy organic prepackaged foods to reduce the risk of consuming foods with unlabelled irradiated ingredients.
Irradiation facilities in Canada include the Nordion Gamma Centre of Excellence in Laval, Quebec which performs food irradiation, and the Johnson & Johnson (medical sterilization) facility in Peterborough, Ontario which is not used for food purposes.
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Canada Gazette. (2002, November). Regulations amending the food and drug regulations (1094 – Food irradiation). Retrieved fromhttp://gazetteducanada.gc.ca/partI/2002/20021123/html/regle1-e.html
Canadian Institute of Food Science and Technology. (1999). CIFST Food Irradiation Background Paper. Retrieved from http://www.cifst.ca/default.asp?id=879
Center for Food Safety and Applied Nutrition – Food and Drug Administration (August 21, 2008). FDA Announces Final Rule Amending the Food Additive Regulations to Allow for the Irradiation of Fresh Iceberg Lettuce and Fresh Spinach. Retrieved fromhttp://www.cfsan.fda.gov/~dms/cfsup185.html
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Codex Alimentarius Commission. (2003). Revised codex general standard for irradiated foods.Retrieved from www.codexalimentarius.net/download/standards/16/CXS_106e.pdf
EUROPA. (2007). Food irradiation – community legislation. Retrieved fromhttp://ec.europa.eu/food/food/biosafety/irradiation/comm_legisl_en.htm
Gomes, C., Moreira, R.G., Castell-Perez, M.E., Kim, J., Da Silva, P. & Castillo, A. (2008). E-Beam Irradiation of Bagged, Ready-to-Eat Spinach Leaves (Spinacea oleracea): An Engineering Approach. Journal of Food Science, 73 (2), E95–E102 doi. 10.1111/j.1750-3841.2007.00629.x
Health Canada. (2005). Food and drug regulations – division 26: food irradiation. Retrieved from http://www.hc-sc.gc.ca/fn-an/legislation/acts-lois/fdr-rad/index_e.html
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International Food Information Council. (2002). Food irradiation: a global food safety tool. Retrieved from http://ific.org/publications/brochures/irradiationbroch.cfm
Levanduski, L. & Jaczynski, J. (2008). Increased resistance of Escherichia coli O157:H7 to electron beam following repetitive irradiation at sub-lethal doses. International Journal of Food Microbiology, 121(3), 328-34.
Nordion. (2011). The history of food irradiation. Retreived from http://www.nordion.com/documents/The-History-of-Food-Irradiation.pdf
O'Bryan, C.A., Crandall, P.G., Ricke, S.C. & Olson, Dennis G. (2008). Impact of irradiation on the safety and quality of poultry and meat products: a review. Critical Reviews in Food Science and Nutrition, 48(5), 442-457.doi: 10.1080/10408390701425698
United States Food and Drug Administration. (2008). Irradiation of food and food packaging. Retrieved from http://www.cfsan.fda.gov/~dms/opairrad.html
Date modified: 2012-07-19