SURVIVAL OF HEAT-SHOCKED YERSINIA-ENTEROCOLITICA AFTER IRRADIATION IN-GROUND PORK

Earlier studies conducted in our laboratory showed that heat-shocked Y ersinia enterocolitica (45 degrees C for 60 min) are more resistant to a subsequent heat treatment of 55 or 60 degrees C in ground pork than cells not previously heat-shocked. The increased thermotolerance was partly attributed to the production of stress proteins. The present st udy was performed to determine if the stress proteins produced by heat ing could also afford protection to the cells to irradiation. As part of the study, the effect of air versus vacuum packaging on survival of Yersinia to irradiation was also examined. Irradiating the inoculated pork at 1.0 kGy was sufficient to completely eliminate this pathogen. The irradiation D value for both heat-shocked and non-heat-shocked ce lls was statistically the same (0.15 kGy). Neither heat-shocking Yersi nia nor packaging under vacuum resulted in increased resistance of thi s organism to irradiation. In addition, no effect was seen in virulenc e of the cells after these treatments, when compared with controls. (C ) 1998 Elsevier Science B.V.