Inactivation of Vibrio parahaemolyticus in shucked raw oyster (Grassostrea gigas) and clam (Venerupis phillippinarum) by using a combination of NaClO and gamma irradiation

Abstract

This study investigated the synergistic effects of sodium hypochlorite (NaClO) and gamma irradiation combination against Vibrio parahaemolyticus in shucked oysters and clams. V. parahaemolyticus decreased to 1.1-5.6 log(10) CFU/g in oysters and 1.1-5.7 log(10) CFU/g in clams by NaClO (20-80 ppm) + gamma irradiation (0.1-2.0 kGy) combinations. V. parahaemolyticus was not detected by 60 or 80 ppm NaClO + 2.0 kGy. Synergistic reduction of >1 log was observed by 60 ppm NaClO + 0.3-2 kGy and 80 ppm NaClO + 0.5 or 2 kGy. Specifically, >2 log of the synergistic reduction was obtained by 60 or 80 ppm NaClO + 2 kGy. Furthermore, using the Weibull model, 5D values (5-log reductions) were calculated for 60 or 80 ppm NaClO + 0.5-0.9 kGy. No significant differences were observed for all sensory parameters between samples of 2.0 kGy + 0-80 ppm NaClO. This study suggests that 60 ppm NaClO + 2.0 kGy in reducing 7-log V. parahaemolyticus without any deteriorative changes of sensory qualities could be a potential strategy for post-harvest process in seafood processing and distribution to enhance the microbial safety of molluscan shellfish.