VIABILITY OF ESCHERICHIA-COLI O157-H7 IN SALAMI FOLLOWING CONDITIONING OF BATTER, FERMENTATION AND DRYING OF STICKS, AND STORAGE OF SLICES

The fate of Escherichia coli O157:H7 was monitored in salami during co nditioning of batter, fermentation and drying of sticks, and storage o f slices. The raw batter (75% pork:25% beef, wt/wt, fat content about 20%) was inoculated with a pediococcal starter culture (about 10(8) CF U/g) and a five-strain cocktail of E. coli O157:H7 (greater than or eq ual to 2 X 10(7) CFU/g) and stuffed into 104-mm diameter fibrous casin gs. After being refrigerated at 4 degrees C or being tempered at 13 de grees C, frozen at -20 degrees C, and thawed at 4 degrees C, or being frozen at -20 degrees C, and thawed at 4 degrees C, the inoculated bat ter was fermented at 24 degrees C and 90% relative humidity (RH) to pH less than or equal to 4.8, dried at 13 degrees C and 65% RH to a mois ture/protein ratio of less than or equal to 1.9:1, and then stored at 4 or 21 degrees C under air or vacuum. For salami sticks sampled immed iately after drying, appreciable differences were evident among the va rious batter-conditioning treatments; pathogen numbers were reduced fr om original levels by 2.1, 1.6, or 1.1 log(10) units when batter was t empered, frozen, and thawed, frozen and thawed, or refrigerated, respe ctively. Similarly, regardless of storage temperature or atmosphere, w ithin 7 days salami slices cut from sticks prepared from batter that w as tempered, frozen, and thawed (2.7- to 4.9-log(10)-unit reduction) o r frozen and thawed (2.3- to 4.8-log(10)-unit reduction) displayed a g reater impact on pathogen numbers than slices cut from sticks prepared from batter that was refrigerated (1.6- to 3.1-log(10)-unit reduction ). The effects of batter conditioning notwithstanding, a greater reduc tion in levels of E. coli O157:H7 was observed when slices were stored at 21 degrees C compared to otherwise similar slices stored at 4 degr ees C. After storage for 60 days the pathogen was only detected by enr ichment in slices stored at 21 degrees C, whereas pathogen levels rang ed from 1.4 to 4.5 log(10) CFU/g in slices stored at 4 degrees C. Diff erences related to storage atmosphere were first observed after slices were stored for 21 days. Such differences were more readily demonstra ble after 60 and 90 days, with pathogen numbers for treatments that we re statistically different ranging from 0.6- to 1.5-log(10) units high er on slices stored under vacuum than in air. These data emphasize the need to implement multiple barriers to appreciably reduce numbers off . coli O157:H7 in salami.