INJURY AND SURVIVAL OF AEROMONAS HYDROPHILA 7965 AND YERSINIA ENTEROCOLITICA 9610 FROM HIGH HYDROSTATIC PRESSURE

Abstract

Responses of Aeromonas hydrophila 7965 and Yersinia enterocolitica 9610 to high hydrostatic pressure were investigated in microbiological media and meat. Cultures were pressurized from 51 to 304 megaPascals (MPa) for 15 min in 200 mM sodium phosphate buffer (pH 7.0), tryptic soy broth and radiation‐sterilized ground pork. Trends in pressure response were similar in all three pressure menstrua. A 7‐log10 CFU/g reduction of A. hydrophila in pork resulted from treatment of 253 MPa for 15 min. A 7‐log10 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 menstrua at most pressure levels. No growth of either pathogen occurred in irradiated 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 upshift 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 suggests that temperature abuse (30C) of pressure‐processed pork for greater than 6 h would allow growth and possibly repair of A. hydrophila and Y. enterocolitica which survive following pressure treatment. Although neither the processor nor the consumer would likely abuse the product to such an extent, the results suggest that A. hydrophila and Y. enterocolitica have the ability to repair or grow following pressure treatment in pork.

The importance of Aeromonas hydrophila in food safety

“…Ellenberg and Hoover (1999) studied the response of A. hydrophila to high hydrostatic pressure (from 51 to 304 megaPascals; MPa) for 15 min. The results showed that the pathogen had the ability to repair or grow following pressure treatment in pork.…”

Modeling the pressure inactivation dynamics of Escherichia coli

“…Most of the common bacterial food-borne pathogens such as Campylobacter jejuni (2), Salmonella (3,4), Vibrio spp. (5), Escherichia coli O157:H7 (4,6), Yersinia enterocolitica (4,7), and Listeria monocytogenes (4)(5)(6)8) have been investigated in a variety of food systems and buffers, at various temperatures and for various pressureholding times. However, much fewer studies have been conducted on high-pressure inactivation of microorganisms, especially foodborne pathogens, than on thermal inactivation, especially in terms of predictive microbiology.…”

Inactivation of Campylobacter jejuni by high hydrostatic pressure

“…1995; Stewart et al. 1997; Ellenberg and Hoover 1999). Generally, the vegetative Gram‐positive organisms are more recalcitrant to pressure inactivation than Gram‐negative bacteria; however, HPP is effective at reducing or eliminating most vegetative forms of bacteria at pressures in the range of 300–800 MPa.…”

“…It offers benefit over traditional thermally processed foods in that micro-organisms and detrimental enzymes can be inactivated by HPP without significant changes in the taste, texture, colour or nutritional value of the food (Shearer et al 2000). Most of the common bacterial food-borne pathogens, such as Salmonella, Vibrio spp., Escherichia coli O157:H7, Yersinia enterocolitica and Listeria monocytogenes, have been investigated in a variety of food systems and buffers, at various temperatures and for various pressure durations (Metrick et al 1989;Styles et al 1991;Patterson et al 1995;Stewart et al 1997;Ellenberg and Hoover 1999). Generally, the vegetative Gram-positive organisms are more recalcitrant to pressure inactivation than Gram-negative bacteria; however, HPP is effective at reducing or eliminating most vegetative forms of bacteria at pressures in the range of 300-800 MPa.…”