Inactivation by Ionizing Radiation of Salmonella Enteritidis, Salmonella Infantis, and Vibrio parahaemolyticus in Oysters (Crassostrea brasiliana)

Abstract

Irradiation is considered one of the most efficient technological processes for the reduction of microorganisms in food. It can be used to improve the safety of food products, and to extend their shelf lives. Oysters are considered one of the most important vehicles for pathogenic bacteria because of their feeding characteristics. The aim of this study was to evaluate the influence of a gamma radiation process on high levels of Salmonella Enteritidis, Salmonella Infantis, and Vibrio parahaemolyticus incorporated by oysters (Crassostrea brasiliana), as well as the effects of the process on the survival of the oysters and on their sensory attributes. The oysters were exposed to gamma radiation (60Co) in doses ranging from 0.5 to 3.0 kGy. A dose of 3.0 kGy was generally sufficient to reduce the level of Salmonella serotypes by 5 to 6 log10 units. A dose of 1.0 kGy was sufficient to produce a 6-log10 reduction in the level of V. parahaemolyticus. The highest irradiation dose did not kill the oysters or affect their sensory attributes. Hence, a dose of 3.0 kGy can be considered effective in inactivating Salmonella and V. parahaemolyticus in oysters without changing their odor, flavor, or appearance.

Susceptibility of Murine Norovirus and Hepatitis A Virus to Electron Beam Irradiation in Oysters and Quantifying the Reduction in Potential Infection Risks

“…Inactivation studies on Salmonella spp. with live oysters showed a relatively low D 10 value of 0.45 to 0.55 kGy (16). Harewood et al (12) reported that virus inactivation required a higher dose of irradiation than bacterial pathogens.…”

“…However, to determine the dose required for complete inactivation of the viruses in the oyster meat, higher E-beam doses were utilized. Gamma radiation as a sanitization treatment for shellfish has been studied by different research groups (12,16,(25)(26)(27)(28). A variety of bacterial pathogens are susceptible to ionizing radiation, such as Vibrio cholerae, V. parahaemolyticus, and V. vulnificus, with D 10 values as low as 0.1 kGy (27,29).…”

“…The U.S. FDA has approved the use of ionizing radiation of up to a maximum of 5.5 kGy as a pathogen intervention strategy to control naturally occurring Vibrio vulnificus in shellfish (15). Currently, only a small percentage of the commercial oysters sold in the United States are being processed by ionizing radiation, such as cobalt-60 (personal communication, Food Technology Services, Inc., Mulberry, FL [16]). Ionizing radiation can be generated using either radioactive isotopes (cobalt-60 or cesium-137) or linear accelerators to generate electron beams (E-beam).…”

Shellfish as reservoirs of bacterial pathogens

“…Other postharvest processing methods include use of high hydrostatic pressure [69], use of supercritical carbondioxide [70], and inactivation of zoonotic bacteria, including Salmonella and Vibrio spp. by ionizing radiation [71]. One study described X-ray inactivation of V. parahaemolyticus and inherent microflora in oysters to less than detectable limit [72].…”

Application of Ionizing Radiation for Control of Salmonella in Food

“…Jakabi et al [68] studied the survival of S. enteritidis and S. infantis inoculated into oysters and sensory properties as the result of irradiation with doses in the dose range of 0.5-3.0 kGy. The number of those both Salmonella populations decreased after a 3.0 kGy dose by five to six logs.…”