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Int.J.Curr.Microbiol.App.Sci (2014) 3(4): 549-555 ISSN: 2319-7706 Volume 3 Number 4 (2014) pp. 549-555 http://www.ijcmas.com Review Article Food Irradiation - Technology and Application B.Kalyani* and K.Manjula Department of Home Science, S.V.University, Tirupati, A.P., India-517502 *Corresponding author A B S T R A C T The technology of food irradiation is gaining more and more attention around the world. In comparison with heat or chemical treatment, irradiation is more effective and appropriate technology to destroy food borne pathogens. Radiation technique Keywords makes the food safer to eat by destroying bacteria which is very much similar to the process of pasteurization. Radiation does not leave the food items radioactive for Radiation, two seasons. First, the gamma rays from cobalt-60 used in food radiation are not technology, energetic enough to make it radioactive. Second, as the food never comes into food, contact with the source directly, it is not possible for the food to become packaging. contaminated with radioactive material. In the changing scenario of world trade, switching over to radiation processing of food assumes great importance. Radiation will be moving fast to the status of a 'wonder technology' to satisfy the sanitary and phyto sanitary requirements of the importing countries. Food once irradiated, can be prone to re-contamination unless appropriately packed Therefore, if radiation treatment is intended to control microbiological spoilage or insect infestation, prepackaging becomes an integral part of the process. Introduction India has been practicing various methods unmanageable distances between the of food preservation from time production and consumption centers and immemorial such as sun drying, pickling the rising gap between demand and supply and fermentation. These methods were have posed great challenges to supplemented with more energy conventional techniques of food consuming techniques like refrigeration, preservation and thereby to food security. freezing and canning; however had its The hot and humid climate of the country merits and demerits. The quest was ever is quite favorable to the growth of on for newer methods of food preservation numerous insects and micro organisms with least change in sensory qualities. which destroy stored crops and cause Preservation of food items is a pre- spoilage of food. In the changing scenario requisite for food security. The seasonal of world trade, switching over to radiation nature of production and the long and processing of food assumes great 549 Int.J.Curr.Microbiol.App.Sci (2014) 3(4): 549-555 importance. Radiation processing can be facilities for radiation processing of food used for disinfestations of pests and in public as well as private sectors. disease-causing organisms from a range of products including fruits and vegetables. The Ministry extends assistance for setting up facilities for food processing by using Radiation as a Preservation Technique radiation technology to promote commercial use of this technology in Radiation is one of the latest methods in India. BARC will be the nodal agency for food preservation. Radiation technique assistance and guidance on process makes the food safer to eat by destroying technology while BARC/BRIT will bacteria which is very much similar to the provide information on availability, cost process of pasteurization. In effect, and possible alternatives of essential radiation disrupts the biological processes machinery including pollution control and that lead to decay and the ability to sprout. disposal of radio isotopes. BARC can Being a cold process, radiation can be provide training to the staff on various used to pasteurize and sterilize foods aspects of operation and safety in India without causing changes in freshness and (saylor, and, Jordan, 2000). texture of food unlike heat. Further, unlike chemical fumigants, radiation does not Radiation Processing leave any harmful toxic residues in food and is more effective and can be used to Food irradiation is a technology that can treat packaged commodities too. be safely used to reduce food losses due to Countries including India guard against deterioration and to control contamination import of exotic insect pests by requiring a causing illness and death. Food irradiation post harvest disinfestations treatment of uses radiant energy electron beams, commodities that can carry pests. India gamma rays or x-rays to rid food of will not be able to resist the flow of harmful microorganisms, insects, fungi radiated foods to the country as a and other pests, and to retard spoilage. It prohibitive policy would be difficult to does not make food radioactive. justify on technical grounds and could be Irradiation kills pathogens and makes them challenged under the WTO agreement as a incapable of reproduction. technical barrier to trade. Above all, There are several processes that are radiation technology for food preservation collectively referred to as Food will be moving fast to the status of a Irradiation . The object of each process is 'wonder technology' to satisfy the sanitary to kill or impair the breeding capacity of and phyto sanitary requirements of unwanted living organisms or to affect the importing countries. product morphology in a beneficial way The Ministry of Food Processing that will extend shelf-life. Each process Industries has a major role to play in has an optimal dose of ionizing energy ensuring food security by processing and (radiation) dependent on the desired effect. preserving food items to be released in The dose of radiation is measured in grays consuming areas and at lean periods. The (Gy). A gray is a unit of energy ministry has a number of schemes to equivalent to 1 joule per kilogram. This encourage entrepreneurs for setting up unit of measure is based on the metric system. Thus, 1 kilogray (kGy) is equal to 550 Int.J.Curr.Microbiol.App.Sci (2014) 3(4): 549-555 1,000 grays (Gy). All three forms of radiation energy is converted to heat ionizing energy have the same effect, gray during treatment, the process typically for gray. Some of the major processes are: increases the product temperature by about 1 degree Celsius(Benebion.). Pasteurization (Pathogen Reduction) Types of Radiation sources Irradiation is used to effectively eliminate disease causing organisms including Three principal types of radiation source bacteria and parasites. (e.g. Irradiating can be used in food irradiation according ground beef to make it safe from E. coli to the O157:H7. Irradiating live oysters to make them safe from vibrio.) Codex Alimentarius General Standard (Food and agriculture organization, world Sterilization Irradiation is used at a very health organization, 1984) : high dose to eliminate all organisms so that refrigeration is not required (shelf (a) Gamma radiation from stable). (e.g. Certain foods are sterilized radionuclides such as 60Co or 137Cs 8; for NASA astronauts.) (b) Machine sources of electron Sanitation Irradiation is widely used to beams with energies up to 10 MeV; reduce organisms for spices, herbs and (c) Machine sources of other dried vegetable substances. (e.g. bremsstrahlung (X rays) with electron Irradiating spice blends that are added to energies up to 5 MeV. meat for hot dogs and other Ready to Eat products that may not be cooked Because of their greater penetrating again.) the population of spoilage causing capability, rays and X rays may be used organisms, including bacteria and mold. for processing of relatively thick or dense On certain fruits and tubers, irradiation products. For situations where only a delays ripening and/or sprouting. (e.g. shallow penetration is needed and where Irradiating berries to reduce mold. rapid conveyor speeds can be used, high Irradiating fresh fruits to extend their power electron beams may provide a market reach. Irradiating potatoes, onions higher output at lower cost per unit of and garlic to impair cell division and product when large amounts of product are hence allow them to go through the off involved. season without sprouting.) Gamma rays Disinfestation Irradiation is used to stop reproduction of both storage and The rays used in food processing are quarantine insect pests.(e.g. Irradiating obtained from large 60Co radionuclide foreign produced mangoes to eliminate the sources. This type of radiation is seed weevil, which is a quarantined pest, essentially monoenergetic (60Co emits for import to the US. Irradiating papaya is simultaneously two photons per to eliminate fruit flies, which are disintegration with energies of 1.17 and quarantined pests, for import from Hawaii 1.33 MeV). Using analytical techniques or foreign countries into the US mainland.) such as the point kernel or Monte Carlo All three forms of irradiation are referred methods, it is possible to compute the dose to as a cold process . Although all of the distribution in irradiated food products 551 Int.J.Curr.Microbiol.App.Sci (2014) 3(4): 549-555 even when very complicated source importance that the dosimetry techniques geometries such as extended plaque used for dose determination are carried out sources are used. The resulting depth dose accurately and that the process is distribution in the food products usually monitored. resembles an approximately exponential curve. Irradiation from two sides (two Food packed in crates or boxes is placed sided irradiation), obtained either by on conveyor belts and moved into the turning the process load or by irradiation heart of the irradiator, where it is exposed from two sides of a plaque source, is often to the radiation source. Electron beam used to increase the dose uniformity in the irradiators can cleanse packaged food at process load (Olivieira, et al., 2000; the end of food-processing production saylor, m.c., jordan, 2000). lines. High-energy waves pass through the food, exciting the electrons in both the Electrons food and any pests or pathogens. When the electrons absorb enough energy, they Electrons emitted by accelerators have break away from their atoms, leaving fairly narrow spectral energy limits positively charged centers behind. (usually less than ±10% of the nominal Irradiation disrupts the molecular energy). The energy of the electrons structure; kills or reduces the number of reaching the product is further controlled bacteria and yeasts; delays the formation by the bending magnets of the beam of mold; and sterilizes or kills parasites, handling system, if applicable. The range insects, eggs and larvae. Levels of of an electron in a medium is finite (unlike absorbed radiation are currently measured that for photons) and is closely related to in kilo grays (kGy). its energy (Hayashi, 1998). Food Irradiation Applications Bremsstrahlung (X rays) The scientific community has defined Bremsstrahlung irradiator design three levels of food irradiation: principles are essentially the same as those for electron irradiators .An extended Applications at low dose levels (10 Gy 1 source of X rays is achieved by kGy) distributing the primary electron beam over a target (X ray converter) of Sprouting of potatoes, onions, garlic, sufficient size. In contrast to the shallots, yams, etc. can be inhibited by radionuclide sources, which emit nearly irradiation in the dose range 20 150 Gy. monoenergetic photons, bremsstrahlung Radiation affects the biological properties (X ray) sources emit photons with a broad of such products in such a way that energy spectrum (Aikawa, Y, 2000; sprouting is appreciably inhibited or Cleland, M.R., Pageau, G.M., 1987). completely prevented. Physiological processes such as ripening of fruits can be The effectiveness of processing of food by delayed in the dose range 0.1 1 kGy. ionizing radiation depends on proper These processes are a consequence of delivery of absorbed dose and its reliable enzymatic changes in the plant tissues. measurement. For food destined for Insect disinfestations by radiation in the international trade, it is of the utmost dose range 0.2 1 kGy is aimed at 552
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