|Fig. 1: This is the international symbol of food irradiation, called the Radura. (Source: Wikimedia Commons)|
Food contamination is a very dangerous threat for humans. In the United States alone, the Food and Drug Administration (FDA) recorded that 12% of species imported to the US were contaminated. The FDA is in control of deciding which foods can be irradiated in the United States.  Across the globe, 42 countries allow irradiation.  From human hair to rodent excrement, it is very easy for contamination in food to occur. The use of radiation has begun to eliminate the threat of food contamination and is now a crucial aspect of the agricultural system. 
The agricultural system has begun to utilize radiation worldwide in order to breed new seed varieties with much higher yields. As shown in Fig. 1, there is an international symbol of irradiation called the Radura. The most common method for irradiation is the use of electromagnetic energy generated by gamma rays from Co-60, a radioisotope of cobalt.  The gamma rays achieve a partial or complete inactivation of cells belonging to the pathogens present in unmodified food.  Another way ionizing energy is used to irradiate is through X-Ray Facilities: the production of radiation through the direction of high energy radiations of very thin metal films with high-energy electron beams. The FDA has improved the use on irradiation to preserve food since 1958.  There are three different cases of food irradiation. The doses of radiation involved in irradiation is measured in kiloGray (kGy). 1000 Joules (the metric unit of energy) per kilogram of a sample mass is equivalent to one dosage of kGy. A low dose is < 1 kGy, a medium dose is 1 - 7 kGy, and a high dose is >25 kGy. Their purposes vary: low doses control parasites and delay ripening, medium doses reduce food borne pathogens, and high doses sterilize.  There are specific doses of kGy required for each individual purpose.
Despite the vast acceptance, there is still debate whether irradiation is useful in the long run for the agricultural system.  When the radiation does take away the negative disease agents, it also has the ability to disrupt the microbes in food.  The effect of radiation on the microbes in food is measured by the D value: The dosage of radiation required to reduce the microbe population of a sample by 90%. The D value can vary depending on the strain of organism involved and the type of food irritated. Taking the D value into consideration is very important in optimizing the effects of irradiation. The ability for microorganisms to survive among irradiation depends on a variety of factors- including extracellular environment conditions, the extent of damage, and the organisms ability to withstand and repair. 
Even with the negative perspective of radiation, the use of irradiation in food is very useful in increasing the productivity of the agricultural system. Taking the D value into consideration, it is important to moderate the kGys to limit the depletion of the nutrients, microbes, and positive agents in food.
© Madison Connell. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. 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.
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