Inactivation of 3-strain cocktail pathogens inoculated into Bajirak jeotkal, salted, seasoned, and fermented short-necked clam (Tapes pilippinarum), by gamma and electron beam irradiation

Abstract

The objective of this study was to determine the efficacy of gamma and electron beam irradiation of the food-borne pathogens including 3-strain cocktail of Listeria monocytogenes (ATCC 19114, 19115, and 19111), Staphylococcus aureus (ATCC 6538, 25923, and 29213), and Vibrio parahaemolyticus (ATCC 17802, 33844, and 27969) in Bajirak jeotkal (8% salt), salted, seasoned and fermented short-necked clam, commercially available in the market. Irradiation (0.5, 1, 2, and 5 kGy) significantly reduced the initial microbial level not only immediately after irradiation but also during storage at 10 degrees C for 4 weeks (P < 0.05). No viable cells were detected at 5 kGy of irradiation at a detection limit of 10(1) CFU/g. Gamma irradiation was more effective than electron beam irradiation, and yielded D-10 values of 0.64, 0.63, and 0.29 kGy for L. monocytogenes, S. aureus, and V. parahaemolyticus, and those of electron beam irradiation were 0.79, 0.81, and 0.36 kGy, respectively. Results suggest that a low dose irradiation can improve the microbial quality and reduce the risk by the food-borne pathogens of Bajirak jeotkal, which has limited alternative sterilization methods due to the temperature characteristics of the products. Furthermore, in practical application, the irradiation source should be considered to obtain an effective dose for decontamination. (C) 2008 Elsevier Ltd. All rights reserved.