Potent Food Preservation: The Practice of Food Irradiation

A commonly understated aspect of food cultivation and processing is the important role of radiation. While it is known that radiation emanating from the sun or microwaves emitted by household kitchen appliances are useful for heating and maintaining food, the lesser-applied forms of ionizing radiation have equally promising utility. The notion of food irradiation as a means of increasing storability and mitigating microbiological growth has been a longstanding focus of research, ever since the discovery of X-rays in the late nineteenth century (Molins, 2001). Today, the commercial prevalence of this food treatment process, along with the analytical techniques used to assess radiation exposure and toxicological effects, contribute immeasurably to the food industry.

Across the electromagnetic spectrum, ionizing radiation is the most commonly employed radiation for food treatment. Specifically, electromagnetic radiation comprised of X-rays and gamma rays, as well as electron-beam radiation, which have sufficient energy to displace electrons and ionize atoms, are used (Lima et al., 2018). In order to use high frequency, ionizing radiation on food, a high-energy radiation source is needed. Typically, radioactive isotopes of cobalt-60 and cesium-137 provide the source of gamma radiation (Farkas, 2006; Lima et al., 2018). The ability of ionizing radiation to directly damage DNA, and incur indirect damage via reactive oxygen species produced by the radiolysis of water facilitates its effectiveness in preserving food (Desouky, Ding, and Zhou, 2015). These mechanisms effectively impede microbial growth by irreparably damaging nucleic acids. However, due to variations in both the chemical and physical structure of microorganisms, effective radiation doses also differ depending on the targeted microbe (Farkas, 2006).

A large area of consideration for the practice of food irradiation is the regulation and quality assurance of the food products. Radiation dose limits and endpoints are heavily controlled, where most commercial applications use less than 10 kGy for a myriad of sterilization, preservation, and pathogenic prevention purposes (Molins, 2001; Farkas, 2006). To closely monitor foods that have undergone irradiation and assess their status, unique chemical markers are analyzed. For example, 2-alkylcyclobutanones (2-ACBs) are a chemical species produced specifically by the irradiation of fatty acids and triglycerides in food (Figure 1) (Crews, Driffield, and Thomas, 2012). As such, their presence in food is directly correlated to the extent of radiation exposure, and analytical methods such as solvent extraction of the lipid fraction or separation and detection of the 2-ACBs with liquid chromatography coupled GC-MS are most commonly adopted in food science laboratories (Crews, Driffield, and Thomas, 2012). These methods exploit the property that 2-ACBs are lipophilic and can be eluted in non-polar solvents. Further modifications to methodologies, such as the use of reference and internal standards, or derivatization, can also be carried out to enhance validation and the accuracy of detection (Crews, Driffield, and Thomas, 2012).

As a whole, food irradiation is a practical technique for preserving food, inhibiting growth of microorganisms, and ensuring successful food quality. By using ionizing radiation, the nutritional content of foods is uncompromised, while its shelf life is improved. Moreover, through the identification of unique markers indicating the extent of irradiation and their quantification using analytical techniques, stringent health policies and regulations are established and enforced. As many other commonplace and fundamental food processing methods, like the heat pasteurization of milk, the implications of food irradiation are widespread.

References

Crews, C., Driffield, M. and Thomas, C., 2012. Analysis of 2-alkylcyclobutanones for Detection of Food Irradiation: Current Status, Needs and Prospects. Journal of Food Composition and Analysis, [online] 26(1-2), pp.1–11. Available at: https://doi.org/10.1016/j.jfca.2011.11.006 [Accessed 21 Oct. 2019].

Desouky, O., Ding, N. and Zhou, G., 2015. Targeted and Non-targeted Effects of Ionizing Radiation. Journal of Radiation Research and Applied Sciences, [online] 8(2), pp.247–254. Available at: https://doi.org/10.1016/j.jrras.2015.03.003 [Accessed 21 Oct. 2019].

Farkas, J., 2006. Irradiation for Better Foods. Trends in Food Science & Technology, [online] 17(4), pp.148–152. Available at: https://doi.org/10.1016/j.tifs.2005.12.003 [Accessed 21 Oct. 2019].

Kimpe, N.D., Verniest, G., Boterberg, S., Colpaert, J., Thienen, T.V. and Stevens, C., 2004. Efficient Synthesis of 2-Substituted Cyclobutanones as Markers for Food Irradiation. Proceedings of The 8th International Electronic Conference on Synthetic Organic Chemistry. [image online] Available at: https://doi.org/10.3390/ecsoc-8-01980 [Accessed 21 Oct. 2019].

Lima, F., Vieira, K., Santos, M. and Souza, P.M.D., 2018. Effects of Radiation Technologies on Food Nutritional Quality. Descriptive Food Science. [online] Available at: https://doi.org/10.5772/intechopen.80437 [Accessed 21 Oct. 2019].

Molins, R.A., 2001. Food Irradiation: Principles and Applications. [online] New York: Wiley. ISBN: 0-471-35634-4 [Accessed 21 Oct. 2019].