Radiosensitization of Salmonella spp. and Listeria spp. in ready-to-eat baby spinach leaves
Posted: January 29th, 2011 - 7:47am
Source: Journal of Food Science
Abstract: The FDA recently approved irradiation treatment of leafy greens such as spinach up to 1 kGy; however, it is important to reduce the dose required to decontaminate the produce while maintaining its quality. Thus, the objectives of this study were: (1) to assess the radiation sensitivities of Salmonella spp. and Listeria spp. inoculated in ready-to-eat baby spinach leaves under modified atmosphere packaging (MAP) and irradiated using a 1.35-MeV Van de Graff accelerator (the leaves were irradiated both at room temperature and at –5 °C); and (2) to understand and optimize the synergistic effect of MAP and irradiation by studying the radiolysis of ozone formation under different temperatures, the effect of dose rate on its formation, and its decomposition. Results showed that increased concentrations of oxygen in the packaging significantly increased the radiation sensitivity of the test organisms, ranging from 7% up to 25% reduction in D10-values. In particular, radiosensitization could be effected (P < 0.05) by production of ozone, which increases with increasing dose-rate and oxygen concentration, and reducing temperatures. Radiosensitization was demonstrated for both microorganisms with irradiation of either fresh or frozen (−5 °C) baby spinach. These results suggest that low-dose (below 1 kGy) e-beam radiation under modified atmosphere packaging (100% O2 and N2: O2[1 : 1]) may be a viable tool for reducing microbial populations or eliminating Salmonella spp. and Listeria spp. from baby spinach. A suggested treatment to achieve a 5-log reduction of the test organisms would be irradiation at room temperature under 100% O2 atmosphere at a dose level of 0.7 kGy.