Injury and survival of Aeromonas hydrophila 7965 and Yersinia enterocolitica 9610 from high hydrostatic pressure

Responses of Aeromonas hydrophila 7965 and Yersinia enterocolitica 9610 to high hydrostatic pressure were investigated in microbiological media and me at. Cultures were pressurized from 51 to 304 megaPascals (MPa) for 15 min i n 200 mM sodium phosphate buffer (pH 7.0), tryptic soy broth and radiation- sterilized ground pork. Trends in pressure response were similar in all thr ee pressure menstrua. A 7-log(10) CFU/g reduction of A. hydrophila in pork resulted from treatment of 253 MPa for 15 min. A 7-log(10) CFU/g reduction of Y. enterocolitica in pork resulted from treatment of 304 MPa for 15 min. Pressure-induced injury of both pathogens was detected in all pressure men strua at most pressure levels. No growth of either pathogen occurred in irr adiated pork after pressurization of 128-203 MPa for 15 min and storage at 4C for 14 days; however, an upshift to 30C of cold-stored A. hydrophila in pork resulted in growth after a lag time of approximately 10 h, and an upsh ift to 30C of cold-stored Y. enterocolitica in pork resulted in recovery of injured cells within 2 h, and growth after a lag time of 4-6 h. This sugge sts that temperature abuse (30C) of pressure-processed pork for greater tha n 6 h would allow growth and possibly repair of A. hydrophila and Y. entero colitica which survive following pressure treatment. Although neither the p rocessor nor the consumer would likely abuse the product to such an extent the results suggest that A. hydrophila and Y. enterocolitica have the abili ty to repair or grow following pressure treatment in pork.