Destruction of Salmonella enteritidis inoculated in liquid whole egg by high hydrostatic pressure: comparative study in selective and non-selective media

The destruction of Salmonella enteritidis inoculated in liquid whole egg at approximately 10(7)-10(8) cfu ml(-1) was studied under combinations of pre ssure (350 and 450 MPa) temperature (50, 20, 2 and - 15 degrees C) and time (5, 10, 15 min and cycles of 5 + 5 and 5 + 5 + 5 min). One non-selective m edium (tryptone soy agar) and two selective media (brilliant green agar and salmonella-shigella) were used to evaluate viability of S. enteritidis aft er pressurization. The inactivation rate increased with pressure and exposu re time, being minimal at 350 MPa and - 15 degrees C for 5 min lover 1 log( 10) of reduction) and reaching total inactivation (8 log(10) of reduction) in several treatments at 50 degrees C. Treatments in cycles showed greater effectiveness than continuous treatments of the same total time. The effect of pressure was enhanced by elevated temperatures. The higher counts were obtained in the non-selective medium, indicating the presence of injured ce lls after pressure treatment. D-values obtained for two temperatures (2 and 20 degrees C) and different times (0-60 min) under controlled pressure (40 0 MPa) showed that microbial inactivation followed a first-order kinetics w ith a decimal reduction time evaluated in tryptone soy agar medium of 9.5 m in at 2 degrees C and 8.8 min at 20 degrees C. (C) 1999 Academic Press.