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| Fig. 1: The International Radura Symbol for Irradiated Food.(Source: Wikimedia Commons) |
To prevent foodborne illness from affecting consumers throughout the world, radiation by gamma rays, electron beams, and x-rays are used to irradiate food such as fresh produce and raw meat. [1-6] This type of food irradiation is sometimes referred to cold- pasteurization because ionizing radiation is used to kill microorganisms that cause foodborne illnesses. [2] Irradiating food inactivates microorganisms by causing random breaks in the nucleic acids, proteins, and key enzymes. [3] As of 2001, 40 countries throughout the world permit the use of food irradiation for one or more types of food. [2] Even astronauts in NASA eat irradiated food into outer space in order to prevent the possibility of contracting a foodborne illness. [4] The goal for employing food irradiation is to reduce or eliminate bacteria, microbes, and viruses from different types of food using three different approved types of radiation sources: gamma rays, electron beams (e-beams), and x-rays. [2-5] Gamma rays are produced using Co-60 and Cs-137. [3,4] E-beam and x-ray sources produce energized electrons that have allowable energies of 10 MeV and 5 MeV respectfully. [3,5,6] This paper will prove or disprove some of the common myths associated with food irradiation such as: it makes the food radioactive, it changes the nutritional value of the food, and that it changes the food's appearance, taste, and texture. [4]
The first myth about food irradiation is that radiating the food with ionizing radiation causes the food to become radioactive. [4] One method to irradiate food is by using gamma rays made from cobalt 60 and cesium-137. [3,4] Electron beams and x-rays are produced to irradiate food by using energized electrons and photons up to 10 MeV for e-beams and 5 MeV for x-rays. [3,5,6] Unlike gamma radiation, which penetrates completely through the food, electrons from an electron beam only penetrates 3 cm to 10 cm beneath the surface of the food depending on the machine parameters. [3] The radiation produced by electrons can cause photonuclear reactions within the food, thus producing neutrons and a very small amount of short-lived radionuclides. [5] Since limits are placed on the energy of the electrons and photons, especially for x-ray sources, the production of radionuclides is insignificant. [5] According to the joint FAO/IAEA/WHO study group, food irradiated at does up to the regulated dose of 10kGy poses no toxicological hazards. [3] Therefore, this research disproves the first myth by concluding that food irradiated by gamma rays, e-beams, and x-rays do not make the food radioactive, and are thus safe for consumers to eat. [3-5]
The second common myth about food irradiation is that food loses its nutritional value after being irradiated. [4] According to the research done by J.F. Diehl et al., "essential amino acids, essential fatty acid, minerals, trace elements, and most vitamins suffer no significant losses in foods irradiated under conditionals of actual or potential commercial applications." [3] Some vitamins are more susceptible than others to exposure of ionizing radiation, like vitamin B1. [3] While these losses from ionizing radiation are generally smaller than certain processes like canning, the losses of the more sensitive vitamins can be minimized by using optimized conditions for the type of food. [3] With the regulated doses of radiation applied to food, loss of most nutrients in irradiated foods is insignificant thus partially disproving the second myth. [3]
The third myth about food irradiation is that radiation causes the loss of appearance, texture, and flavor. [4] At current regulated radiation doses, the appearance, texture, and flavor are not known to change in any type of the food. [4] However, when the electron beam doses are increased to above regulation limit to eliminate certain microorganisms, certain studies found that depending on the type of food, the appearance, texture, and flavor was diminished. [6] An example is the study using e-beams to eliminate the human norovirus surrogate MNV-1, on cabbages and strawberries. [6] When the e-beam dosage was increased to levels greater than regulated limits to reduce the active MNV-1, there was a reported change in the color, texture, and flavor of the strawberries, but the cabbages remained the same. [6] Thus, at regulation radiation does for each different type of food, the third myth about food irradiation is disproved. [4,6]
Food irradiation is a process created to prevent foodborne illness by the use of gamma rays, electron beams, or x-rays to reduce or eliminate the disease carrying microorganisms. [2-6] Effective radiation dose varies based on the type of food and microorganism contaminating the food. [1-3] While all of these radiation sources do not cause the food to become radioactive, the nutritional value as well as the appearance, texture, and flavor of the irradiated food is dependent on the radiation dosage. [1-6] Therefore, it is imperative that research is done to determine the effective radiation dosage and source for each type of food being irradiated.
© Andrea Eller. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] J. F. Diehl, C. Hasselmann, and D. Kilcast, "Regulation of Food Irradiation in the European Community: Is Nutrition an Issue?" Food Control 2, 212 (1991).
[2] R. A. Molins, Y. Motarjemi, and F. K. Käferstein, "Irradiation: a Critical Control Point in Ensuring the Microbiological Safety of Raw Foods," Food Control 12, 347 (2001).
[3] J. Farkas, "Irradiation For Better Food," Trends Food Sci. Tech. 17, 148 (2006).
[4] "Food Irradiation," U.S. Environmental Protection Agency, EPA 402-F-06-046, April 2006.
[5] D. J. S. Fidlay, T. V. Parsons, and M. R. Sené, "Irradiation of Food and the Introduction of Radioactivity," Radiat. Phys. Chem., 42, 417 (1993).
[6] G. C. Sanglay et al., "Electron-Beam Inactivation of a Norovirus Surrogate in Fresh Produce and Model Systems," J. Food Prot. 74, 1155 (2011).
