The outbreak of food borne infections due to bacterial species such as Clostridium botulinum or viruses like Calcivirus causes several fatal health problems and necessitates a food sterilization process and one such technique is irradiation which is to ionize radiation to destroy pathogenic bacteria, viruses and other microorganisms. Irradiation increases shelf life of treated foods, and prevents overuse of harmful pesticides and insecticides. However, there have been political issues in its actual use in U. K with the dosage applicable for select foods only owing to mutations and aberrations it may cause on reacting with DNA.
Two prime issues that arise here are safety and economic feasibility. As with the former, contrary to popular belief, irradiation does not produce any additional chemicals, or cause changes in odour, colour, texture or taste. From an economic standpoint, it can be argued that despite all costs incurred in the actual process, irradiation supports globalization for food production and distribution. Besides, being a fool-proof automated process to remove all pathogens from food, food irradiation is the way to go and should be applicable to all foods in U.
K in addition to the already existing products. Introduction: The food that we consume must be sterilized in order to eliminate the pathogenic microorganisms that thrive on them through the process of cultivation, processing, packaging, transportation etc. There have been so many outbreaks of food-borne diseases due to the consumption of contaminated foodstuffs by masses. For instance, the typhoid that resulted due to contaminated corned beef in 1964 in Aberdeen (Walker. W, 1965) affecting more than 400 cases, many instances of food poisoning and BSE (Bovine Spongiform Encephalopathy) outbreaks.
Some other common food-borne infections due to bacterial species such as Clostridium botulinum, Campylobacter, Salmonella, E. coli 0157:H7 etc, viruses like Calcivirus and parasitic microorganisms like Giardia lamblia, Cryptosporidia cause severe health problems and can be fatal when untreated. This necessitates a process which is efficient to sterilize food appropriately. There are several methods that have been adopted for food sterilization since time immemorial, such as cooking (heating), chemical preservatives, pasteurization and so on.
One of the methods introduced for sterilizing food since the last decade is the use of radiations. Irradiation: Radiation is a term used to describe the wave energy in space. Irradiation refers to the process of exposing a substance to the action of electromagnetic (ionizing) radiation like electron beams, gamma rays, X rays and so on. Food irradiation, also called cold pasteurization, is done in order to destroy pathogenic bacteria, viruses, other microorganisms and insects in food. Irradiation also increases the shelf life of treated foods and prevents early ripening of fruits, germination of potatoes, onions and garlic.
This method of sterilization, in addition to being economical also prevents the overuse of the harmful pesticides and insecticides. The use of this method in UK, however, has always reflected the political attitude towards nuclear energy trapping. The radiations used for sterilization of food are briefly discussed below: Electron beams are streams of high energy (excited state) electrons (the negatively charged particles of the atom) which are propelled through devices called electron guns. They can penetrate to a few centimetres into food. Soft electrons (Baba. T et al.
’04) of strength of less than 300eV have been used for sterilizing canned foods (grains, beans and spices). X rays, the high frequency electromagnetic radiation (30 PHz-30EHz) with wavelengths ranging between 10-0. 01nm, are produced when high energy electrons strike a metal target. X rays pass through thick foods and require shielding for safety. X rays from 7. 5MeV electrons have been proved to be safe and effective and is also economical (Gregoire. O et al. , ’03). Gamma rays, the high energy photons, have the shortest wavelength and most energy in the electromagnetic spectrum.
In food sterilization, these rays are released by a radioactive substance, either Cobalt 60 or Cesium 137 and are the most effective form of radiation to kill the pathogenic microorganisms such as Salmonella species, Campylobacter species etc in food. The only source of radiation permitted for use in the U. K is the gamma rays from Cobalt-60. Fig 1 – a typical food irradiation facility. Cobalt-60, the source for gamma rays has a half life of 5. 3 years. It is produced by neutron bombardment of Cobalt-59 in a nuclear reactor. When not in use, this radioactive material is stored in water, which totally absorbs all the emitted radiations.
For irradiation, the material is taken out of water into a chamber of doubly protected concrete walls and the food to be sterilized is exposed to the radiations. This method of sterilization, in addition to food products is extended to medical equipments and products and also used in the treatment of cancer. The dosage used for food irradiation in UK is approved by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR 1993; pp. 680–682). The radiation dose absorbed is measured with the S. I unit gray (Gy) and a dose is considered “low” if it does not exceed 0.
2 Gy. Doses above 0. 2 Gy are divided into “intermediate” 0. 2 – 2. 0 Gy and “high” >2 Gy. Mechanism of the radiations in sterilization of food: Food absorbs the energy when exposed to the high energy radiations and the amount of this absorbed energy is called “absorbed dose” or just dose. The high energy particles collide with the atoms of food to result in the formation of free radicals, which by definition are atoms with at least one unpaired electron in the outermost shell and is capable of independent existence (Karlsson, J. ’97) and are highly reactive.
These radicals induce the formation of reactive oxygen intermediates due to oxidative stress in microorganisms which results in programmed cell death. Example O2. – (superoxide) can combine with salicylic acid or with the inhibitors of protein synthesis in the pathogen and cause cell death. The electromagnetic radiation also interacts with the DNA of the microorganisms to induce mutations, aberrations, micronuclei etc and cause lethal effects to the pathogens. Safety issues: The research centres for testing the safety of food irradiation were located at the Leatherhead food RA, Queen’s University Belfast and Reading University.
Food irradiation is done by subjecting food (usually packed in cans or just bulk) to specific measured units of radiation. Contrary to the myth that irradiation increases radioactivity in food, it has been proved that irradiation is absolutely safe. Food irradiation does not produce any new chemical in food, causes a minimal loss of vitamins (as in the case of the use of any method of preservation) and no loss of minerals. The process does not cause a change in the odour, texture, taste and appearance of irradiated food.
Extensive research was conducted to study the safety of food irradiation and in 2003 the method was approved to meet the standards of International Atomic Energy Agency (IAEA) and the Food and Agriculture Organization (FAO) of the United Nations Organization. The guidelines for the use of irradiation in phytosanitation were approved by the Interim Commission for Phytosanitary Measures. 60 countries throughout the world have been using irradiation for foodstuffs like grains, spices, beef, fruits and vegetables, chicken, fish and other seafood.
However, in the UK, presently only correctly labeled irradiated herbs, spices or vegetable seasonings are permitted (Directive 99/2/EU and Directive 99/3/EU). And the EC directive 1999/2/EC requires all foods and its ingredients to be labeled as “irradiated” or as “treated with ionizing radiation”. Economics: The food crops and other agricultural commodities that are exported are a major challenge to the agencies that control food safety to ensure that the food is safe for consumption and nutritious in the importing nation.
Thorough studies on this matter by various agencies have proved that irradiation of food is a boon for ensuring food safety, security and trade. There exists the need to assure enhanced security at the irradiation plants, which is only going to add on further to the overhead that’s being incurred and there in reflect in the actual irradiated commodities as being high priced. Despite all these costs, the key point to note here is that irradiation supports greater globalization of food production and distribution. Conclusion:
Extensive research has been conducted on the use of radiations for sterilization of food products and the process has been thoroughly analyzed for safety by various organizations all over the world and it can be concluded that food irradiation is a breakthrough for globalization of food trade. Hence serious considerations must be made to extend its use to more products for sterility combined with economic benefit. References Baba. T, Kaneko. H and Taniguchi. S Nissin-High Voltage Co. , Ltd. (NHV), Kyoto, Japan Radiation Physics and Chemistry Volume 71, Issues 1-2, September-October 2004, Pages 209-211.
Committee on an Assessment of CDC Radiation Studies, Board on Radiation Effects Research, Commission on Life Sciences, National Research Council-RADIATION DOSE RECONSTRUCTION for Epidemiologic Uses, National Academy Press Washington, D. C. 1995. Gregoire O, Cleland M. R, Mittendorfer. J, Vander Donckt. M and Meissner. J, Ion Beam Applications (IBA s. a. ), Chemin du Cyclotron 3, 1348, Louvain-la-Neuve, Belgium High Tech Consulting, Anton Bruckerstrasse 6, 4600, Wels, Austria Meissner Consulting GmbH, Angererstrasse 36, 80796, Munich, Germany.
Radiological safety of medical devices sterilized with X-rays at 7. 5 MeV. Radiation Physics and Chemistry. Volume 67, Issue 2, June 2003, Pages 149-167. Kilcast. David – Industrial attitudes to food irradiation in the EU: addressing consumer opinion. Leatherhead Food Research Association. Loaharanu. P, Thomas. P- Irradiation for Food Safety and Quality, Food and Agriculture Organization of the United Nations, International Atomic Energy. Mazel. A, and Levine. A-Induction of cell death in Arabidopsis by superoxid