Inactivation of Avirulent Yersinia pestis in Beef Bologna by Gamma Irradiation†

Abstract

Yersinia pestis, a psychrotrophic pathogen capable of growth at refrigeration temperatures, can cause pharyngeal and gastrointestinal plague in humans that consume contaminated foods. Because Y. pestis is listed as a select agent for food safety and defense, evaluation of food safety intervention technologies for inactivation of this pathogen is needed. Ionizing (gamma) radiation is a safe and effective intervention technology that can inactivate pathogens in raw and processed meats, produce, and seafood. In this study, we investigated the effect of temperature on the ability of ionizing radiation to inactivate avirulent Y. pestis in beef bologna. The mean (±standard error of the mean) radiation D10-values (the radiation dose needed to inactivate 1 log unit or 90% of the population of a microorganism) for avirulent Y. pestis suspended in beef bologna samples were 0.20 (±0.01), 0.22 (±0.01), 0.25 (±0.02), 0.31 (±0.01), 0.35 (±0.01), and 0.37 (±0.01) kGy at temperatures of 5, 0, −5, −10, −15, and −20°C, respectively. When incorporated into a three-dimensional mesh, the predictive model followed a parabolic fit (R2 = 0.84), where the log reduction = −0.264 − (0.039 × temp) − (3.833 × dose) − (0.0013 × temp2) − (0.728 × dose2). These results indicate that ionizing radiation would be an effective technology for control of Y. pestis in ready-to-eat fine emulsion sausage products.