Gamma radiation, food irradiation using

Gamma radiation from cobalt-60 can be used to irradiate food to keep it from spoiling. 

One of the more controversial uses of radioactive nuclides is in food irradiation. Objective 32 Gamma ray beams, X rays, and electron beams have been directed at food for a variety of purposes. Radiation inhibits the sprouting of potatoes and onions, retards the growth of mold on strawberries, and kills bacteria in poultry and fisb. Cobalt-60 and cesium-137 have been used for these purposes. The controversy lies in whether the radiation causes changes in the food that could have adverse health consequences. 

Cobalt-60. Cobalt-60 emits gamma and beta radiation and has a half-life of 5.26 years. Used to sterilize surgical instruments and to improve the safety and reliability of industrial fuel oil burners. Used in cancer treatment, food irradiation, gauges, and radiography. 

The dichromate dosimeter solution is of importance mainly for radiation sterilization and food irradiation applications both for gamma and electron dosimetry. Due to its very good reproducibility, the system is classified as a reference standard system (ASTM E 2628-2009) in the 5-50 kGy dose range and used widely also as a transfer standard dosimeter. 

In Chapter 7 (A Chemist Looks At Zapping Hamburger with Gamma Rays) there is a discussion of how gamma radiation is used to kill bacteria in food. As indicated in the feature, there is concern on the part of some people that the irradiated food is radioactive. Why is this not the case If you wanted to make the food radioactive, what would you have to do ... 

The radioisotope cobalt-60, with a half-life of 5.27 years (1925.3 days) through beta ((3) emission, decays to form the stable element nickel-60. It is used to test welds and metal casts for flaws, to irradiate food crops to prolong freshness, as a portable source of ionizing gamma (Y) radiation, for radiation research, and for a medical source of radiation to treat cancers and other diseases. 

Irradiation. Ionizing radiation for use in food systems can come from electrons, x-rays, or gamma rays from cobalt-60 or cesium-137. There is little rise in the temperature within the foodstuff, so heat destruction of nutrients is minimized. However, free radicals and peroxides are formed within the food. In the United States, irradiation is classified as a food additive and its use in the food industry has been severely restricted to such areas as prevention of potato sprouting and wheat infestation. 

Administration (FDA), for example, requires testing of all new drugs, and 80 percent of that testing employs radioisotopes. But radiation is also widely used to treat products, especially in agriculture, where an irradiation process exposes food to gamma rays from a radioisotope of cobalt 60 to eliminate potentially harmful or disease-causing elements. Even livestock products are covered. Like its counterparts in at least ten other countries, the FDA approves the use of irradiation for pork, poultry, and red meat as well as for fruits, vegetables, and spices in order to kill bacteria, insects, and parasites that can lead to such diseases as salmonella and cholera. 

For irradiation, the ionizing radiation used are gamma rays, generated from the decay of radioisotopes cobalt 60 or cesium 137, X rays, and electrons, the latter two generated by machines for such purposes. The operators of equipment involving ionizing radiation need to be protected from its effects. The ability subsequently to pasteurize or irradiate food should not compensate for best practices to minimize contamination of food before treatment. Moreover, treated food also needs to be protected from subsequent contamination. 

The Food and Drug Administration (FDA) has approved the use of 0.3 kGy to 1 kGy of radiation produced by cobalt-60 or cesium-137 for the treatment of foods. The irradiation technology is much like that used to sterilize medical supplies. Cobalt pellets are placed in stainless steel tubes, which are arranged in racks. When food moves through the series of racks, the gamma rays pass through the food and kill the bacteria. 

Another potential application of radioactive species is in food preservation (Figure 18.4). It is well known that gamma rays can kill insects, larvae, and parasites such as trichina that cause trichinosis in pork. Radiation can also inhibit the sprouting of onions and potatoes. Perhaps most important from a commercial standpoint, it can extend the shelf lives of many foods for weeks or even months. Many chemicals used to preserve foods have later been shown to have adverse health effects, so irradiation is an attractive alternative. Finally, irradiation can destroy microorganisms such as E. coli (which explains its use in treating beef) and anthrax (which explains its use in sterilizing suspected mail). 

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