DESTRUCTION OF ESCHERICHIA-COLI O157-H7 AND SALMONELLA-TYPHIMURIUM INLEBANON BOLOGNA BY INTERACTION OF FERMENTATION PH, HEATING TEMPERATURE, AND TIME

Fermented meats have caused food-borne illness due to enterohemorrhagi c Escherichia coli. Consumption of Lebanon bologna was epidemiological ly associated with a recent outbreak of salmonellosis. The present stu dy was conducted to determine the effects of pH (after the fermentatio n step), final heating temperature, and time on destruction of E. coli O157:H7 and Salmonella typhimurium in Lebanon bologna. Raw Lebanon bo logna mix was inoculated with either of the pathogens (ca. 10(8) CFU/g ) and fermented for 12 h at 80 degrees F (26.7 degrees C) and then at 100 degrees F (37.8 degrees C) until the pH reached either 5.2 or 4.7. The mix was then heated to 110, 115, or 120 degrees F (43.3, 46.1, or 48.9 degrees C). The bologna was sampled at various times, decimally diluted, and plated on either McConkey sorbitol agar or XLD agar to en umerate E. coli O157:H7 and S. typhimurium, respectively. Fermentation alone reduced populations of both pathogens by <2 log units and heati ng alone reduced populations of E. coli O157:H7 by < 3 log units. A co mbination of fermenting to either pH 5.2 or 4.7, followed by heating a t 110 degrees F (43.3 degrees C) for 20 h, 115 degrees F (46.1 degrees C) for 10 h, or 120 degrees F (48.9 degrees C) for 3 h reduced popula tions of both pathogens by >7 log units. Overall, S. typhimurium cells were either equally or significantly less resistant (P < 0.01) than c ells of E. coli O157:H7. Significant interactions (P < 0.01) among the three factors for the destruction of E. coli O157:H7 were observed. A process-specific regression equation was developed to predict the des truction of E. coil O157:H7 in Lebanon bologna.