Food irradiation
(Redirected from Radurization)
Food irradiation is the process of exposing food to ionizing radiation in order to disinfest, sanitize, sterilize, or preserve food. It is, like most technology involving ionizing radiation, the subject of some controversy regarding its safety. Irradiation is used on other things as well, such as medical hardware. Largely to avoid consumer fear of the term "radiation", it is often called cold pasteurization to emphasize its similarity to the process of pasteurization—treatment of solid food by ionizing radiation can provide an effect similar to heat pasteurization of liquid foods, such as milk.
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Food irradiation
By irradiating food, depending on the dose, some or all of the microbes, fungi, viruses or insects present are killed. This prolongs the life of the food in cases where microbial spoilage is the limiting factor in shelf life. Some foods (e.g., herbs and spices) are irradiated at such high doses (5 kilograys or more) that they are partially sterilized. It has also been shown that irradiation can delay the ripening or sprouting of fruits and vegetables and replace the need for pesticides.
The United Nations Environmental Program passed the Montreal Protocol on Substances that deplete the Ozone Layer banning amongst other substances all non-critical uses of methyl bromide, the most common fumigant for post-harvest quarantine treatment of fruit. Although in theory still permitted for quarantine applications, prices of the fumigant have increased dramatically as a consequence. Some governments and corporations think that irradiation is a legitimate replacement for such fumigants and in consequence some large agricultural nations of the world are currently building irradiation facilities for fresh fruit, although the food industry has been slow to adopt this technology on any large scale.
The United States Department of Agriculture has approved irradiation technology as an alternative treatment for fruits and vegetables that are considered hosts to a number of fruit flies and seed weevils. The United Nations Food and Agricultural Organization (FAO) have passed a motion to support this step committing the member states to implement this technology for their national phytosanitary programs.
Processes
While the term irradiation pertains to all forms of treating food products with ionizing radiation, specific types of radiation treatments are used in the food industry today.
Radurization
Radurization is the process of pasteurization by the use of radiation. It is primarily used to treat foods that have a high moisture content and a high pH. The microbes that are targeted are mainly spoilage organisms. Meat and fish are the foods for which this process is mainly used. For drier, acidic foods, yeasts and molds can be denatured. The treatment dose for radurization is approximately 1 kGy.
Radicidation
The process of radicidation is used to eliminate pathogens. This process kills vegetative cells only, meaning that it will not kill spores. Also, certain radiation-resistant vegetative cells can survive, including some strains of the bacterium Salmonella which have been found to be radiation-resistant. Refrigeration is required for the product post-treatment. The dose for radicidation ranges from 2.5 - 5.0 kGy. At this level some physical and chemical changes may be detected, depending on the type of food. For example, leafy vegetables such as lettuce are more sensitive to irradiation than foods with a tougher consistency.
Radappertization
Radappertization involves treating the product to levels of radiation of approximately 30 kGy. This high level of radiation kills all vegetative cells and also destroys spores from organisms such as Clostridium botulinum. Such levels are generally deemed sufficient for clinical sterility, but not usually employed on food items. Based on recommendations of the International Consultative Group on Food Irradiation many nations limit doses to 10kGy for many food items.
Technologies
Electron beam irradiation
Electron beam irradiation uses electrons accelerated in an electric field to a velocity close to the speed of light. International and national regulations limit the energy of the beam to guarantee that no induced radioactivity occurs. Electrons have cross sections many times larger than photons, so that they do not penetrate the product beyond a few inches, making it necessary to treat fruit and vegetables individually; on the other hand, treatment times are only a few seconds. Electron facilities rely on substantial concrete shields to protect workers and the environment from radiation exposure.
Gamma radiation
Gamma radiation is radiation of photons in the gamma part of the spectrum. The radiation is obtained through the use of radioisotopes, generally cobalt 60 or in very few cases caesium 137. It is the most cost-effective technology and is preferred by many processors because the good penetration enables administering treatment to entire industrial pallets or totes, greatly reducing the need for material handling. A pallet or tote is typically exposed for several minutes depending on dose. The environment is protected by a large concrete shield. With most designs the radioisotope can be lowered into a water storage pool in order to allow maintenance personnel to enter the radiation shield. In this mode the water in the pool absorbs practically all radiation providing a safe working environment for plant personnel. Other not commonly used designs feature dry storage by providing movable shields that eliminate radiation levels in areas of the irradiation chamber.
One variant of gamma irradiators keeps the cobalt 60 under water at all times and lowers the product to be irradiated under water in hermetic bells. No shielding is required for such designs.
X-Ray irradiation
Similar to gamma radiation, x-rays are a substitute for the former. These systems are scalable and have good penetration, with the added benefit of using an electronic source that stops radiating when switched off. They also permit very good dose uniformity. However these systems require a great deal of electrical energy when operating, and exposure times are longer than with gamma rays. Like most other types of facilities, X-Ray systems rely on concrete shields to protect the environment from radiation.
Public perception
The effects of food irradiation have been studied for over 60 years.
Loss of trace nutrients and changes to flavor/odor/texture
At very high doses, e.g. >6 kilogray, irradiation can reduce the vitamins and other essential nutrients; and negatively impact the flavor, odor and texture of food. At the doses typically used in irradiation treatment of food, e.g. <3.5 kilogray, these changes appear minimal. Independent scientific research on the subject has been extensive leading to endorsement of food irradiation by the US Food and Drug Administration, the United States Department of Agriculture and the U.N. World Health Organization as a safe, effective process.
Mishandling of food
Concerns have been expressed by public health groups that irradiation, by killing all bacteria in food, can serve to disguise poor food-handling procedures that could lead to other kinds of contamination. However, processors of irradiated food are subject to all existing regulations, inspections and potential penalties regarding plant safety and sanitization, including fines, recalls and criminal prosecutions.
Radiation safety
Whenever dealing with nuclear technology, safety is a valid concern. The safety of irradiation facilities is assessed by the United Nations International Atomic Energy Agency and national Nuclear Regulatory Commissions. The incidents that have occurred in the past are documented by the agency and thoroughly analyzed to determine root cause and improvement potential. Such improvements are then mandated to retrofit existing facilities and future design. In general the international irradiation industry has an above average track record for worker and environmental safety compared to other heavy industry.
In general the isotopes end energy sources that are permitted by international and national regulation are such as to make it impossible to induce radioactivity in the treated product. Care must be taken not to expose the operators and the environment to radiation and interlocks and safeguards are mandated to minimize this risk. Nevertheless there have been radiation related deaths and injury amongst workers of such facilities many of them involving those operators to override such interlocks.
The incident in Decatur, Georgia where water soluble caesium-137 leaked into the source storage pool requiring a major clean-up effort has led to near elimination of this radioisotope in benefit of the more costly but intrinsically safer, non water soluble, cobalt-60.
See also List of civilian radiation accidents.
Formation of exotic chemicals within food
The work of Dr. Henry Delincee and Beatrice-Luise Pool Zobel is often cited regarding the unknown cancer risk of radiolytic byproducts such as 2-dodecylcyclobutanone or 2DCB as a source of concern. On several occasions has Dr. Delincee clarified that he does not agree with the interpretation of such citations[1],[2]. Furthermore it has been established by the World Health Organization that sufficient research has been conducted to conclude that "based on the current scientific evidence, including the long-term feeding studies, 2-DCB and 2-alkylcyclobutanones in general do not appear to pose a health risk to consumers."[3]Lastly any specific findings are specific to foods that contain triglycerides (the main constituent of vegetable oil and animal fats) excluding many foods commonly irradiated from such concerns altogether. FDA has asked for repeated and conclusive testing of mutagenicity of 2DCBs in irradiated meat. An October 2005 study concluded that "No 2-DCB induced mutagenesis was observed in any of the test systems, both with and without exogenous metabolic activation" confirming previous findings [4].
Labeling
Labeling laws differ from country to country. In the US as in many other countries labeling regulations require the usage of the Radura symbol at the point of sale together with usage of the word "irradiated" or "treated by irradiation". However, the meaning of the label is not consistent. The amount of irradiation used can vary and since there are no published standards, the amount of pathogens affected by irradiation can be variable as well. In addition, there are no regulations regarding the levels of pathogen reduction that must be achieved. Food that is processed as an ingredient by a restaurant or food processor is exempt from the labeling requirement.
Economics
Widespread food irradiation is credited for some economic benefits. Some foods, particularly fruits and vegetables, are naturally restricted from sale on the global market, unless they are irradiated to prolong quality for transportation. Less spoilage at the receiving end means fewer discards, lowering the unit cost. Irradiation has also been used to reduce bacteria counts in seafood that is shipped over long distance.
Critics point out that the greatest food losses occur in warm, moist, lesser-developed countries, where the capital is lacking for existing storage technologies such as refrigeration, and other atmospheric controls. It might therefore be questionable if the most affected countries possess the resources to employ this technology. According to the IAEA registry, however, more and more facilities are licenced in such regions.
Food irradiation does not provide a total solution to food safety, it is one alternative in a variety of food processing techniques. Irradiation can not undo the effects of spoilage that has already occurred prior to treatment. Most national regulations therefore do not permit a decrease in hygienic standards in food handling if a product is to be irradiated, but rather demand the same hygenic standards prior to treatment. Food irradiation therefore can add to the complexity and cost of food processing if it does not replace any more costly alternative process. It should also be noted that irradiation does not prevent re-infestation or contamination of a product if exposed to the pathogen after treatment.
Insect pests can have a devastating effect on crop production. They can also transmit diseases that destroy crops and kill livestock and people. Heavy reliance on pesticides raises environmental concerns and problems of pest adaptation and resistance. As a result, many countries are seeking to minimize insecticide use through irradiation techniques.
Alternatives
There are many alternative methods of food preservation, such as Ultra-high temperature processing, Vacuum Packing and Flash freezing. However, none can be so uniformly applied to such a wide range of foods as irradiation. Critics have stated that changes in Western dietary habits, especially in relation to the seasonal availability of fresh produce, could eliminate the need for irradiation.
Irradiation is sometimes used to facilitate the long distance shipments of food that may contain bacteria which could cause spoilage if the food is not sold quickly. In that sense it is feared by some critics that irradiation may negatively contribute in the effects of globalization claiming that local and seasonal production may be a more effective, safer approach toward food safety.
References
- Sipher, A.T. Food Irradiation: An FDA Report. FDA Papers, Oct. 1968
- Delincee, H. and Pool-Zobel, B. Genotoxic properties of 2-dodecylcyclobutanone, a compound formed on irradiation of food containing fat. Radiation Physics and Chemistry
- WHO Statement on 2-Dodecylcyclobutanone and Related Compounds
Sommers, C.H. 2005. Toxicology Testing Of The Unique Radiolytic Product 2-Dodecylcyclobutanone
Diehl, J.F., Safety of irradiated food, Marcel Dekker, N.Y., 1995 (2. ed.)
Satin, M., Food irradiation, Technomic, Lancaster, 1993 (2. ed.)
Urbain, W.M., Food irradiation, Academic Press, Orlando, 1986
Molins, R. (ed.), Food irradiation - Principles and applications, Wiley Interscience, N.Y., 2001
Sommers, C.H. and Fan, X. (eds.), Food Irradiation Research and Technology, Blackwell Publishing, Ames, IA, 2006
WHO-publications:
anon., Food irradiation - A technique for preserving and improving the safety of Food, WHO, Genf, 1988
anon., Wholesomeness of irradiated food, WHO, Genf, Technical Report Series no. 659, 1981
anon., Safety and nutritional adequacy of irradiated food, WHO, Genf, 1994
anon., High-dose irradiation: Wholesomeness of food irradiated with doses above 10 kGy, WHO, Genf, 1999, Technical Report Series no. 890
See also
External links
- Irradiation FAQ provided by PHYTOSAN S.A. de C.V.(www.phytosan.com)
- Irradiation technology provided by PHYTOSAN S.A. de C.V. (www.phytosan.com)
- Comment by Dr. Henry Delincee on an Affidavit misrepresenting the conclusions of his study on unique radiolytical byproducts.
- Comment by Dr. Henry Delincee on Activists interpretations of work on 2-dodecyclcyclobutaneone
- Comment by Dr. Henry Delincee towards public citizen publications
- WHO Statement on 2-Dodecylcyclobutanone and Related Compounds
- Sommers, C.H. 2005. Toxicology Testing Of The Unique Radiolytic Product 2-Dodecylcyclobutanone.
Categories
Food preservation | Foodborne illnesses