Viability of Escherichia coli O157:H7 in Salami Following Conditioning of Batter, Fermentation and Drying of Sticks, and Storage of Slices

Abstract

The fate of Escherichia coli O157:H7 was monitored in salami during conditioning of batter, fermentation and drying of sticks, and storage of slices. The raw batter (75% pork: 25% beef, wt/wt, fat content about 20%) was inoculated with a pediococcal starter culture (about 10(8) CFU/g) and a five-strain cocktail of E. coli O157:H7 ( > or = 2 x 10(7) CFU/g) and stuffed into 104-mm diameter fibrous casings. After being refrigerated at 4 degrees C or being tempered at 13 degrees 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 batter was fermented at 24 degrees C and 90% relative humidity (RH) to pH < or = 4.8, dried at 13 degrees C and 65% RH to a moisture/protein ratio of < or = 1.9:1, and then stored at 4 or 21 degrees C under air or vacuum. For salami sticks sampled immediately after drying, appreciable differences were evident among the various batter-conditioning treatments; pathogen numbers were reduced from original levels by 2.1, 1.6, or 1.1 log10 units when batter was tempered, frozen, and thawed, frozen and thawed, or refrigerated, respectively. Similarly, regardless of storage temperature or atmosphere, within 7 days salami slices cut from sticks prepared from batter that was tempered, frozen, and thawed (2.7- to 4.9-log10-unit reduction) or frozen and thawed (2.3- to 4.8-log10-unit reduction) displayed a greater impact on pathogen numbers than slices cut from sticks prepared from batter that was refrigerated (1.6- to 3.1-log10-unit reduction). The effects of batter conditioning notwithstanding, a greater reduction 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 degrees C. After storage for 60 days the pathogen was only detected by enrichment in slices stored at 21 degrees C, whereas pathogen levels ranged from 1.4 to 4.5 log10 CFU/g in slices stored at 4 degrees C. Differences related to storage atmosphere were first observed after slices were stored for 21 days. Such differences were more readily demonstrable after 60 and 90 days, with pathogen numbers for treatments that were statistically different ranging from 0.6- to 1.5-log10 units higher on slices stored under vacuum than in air. These data emphasize the need to implement multiple barriers to appreciably reduce numbers of E. coli O157:H7 in salami.

Effects of Acid Adaptation of Escherichia coli O157:H7 on Efficacy of Acetic Acid Spray Washes To Decontaminate Beef Carcass Tissue

“…Conner and Kotrola (13) reported that the presence of organic acids, including acetic, citric, and lactic acids, in broth medium held at 4°C enhanced the survival of E. coli O157:H7, compared to its survival in unacidified control medium held at the same temperature. Likewise, other works have demonstrated that once induced, the acid tolerance of this pathogen is enhanced or maintained longer when the organism is held at colder temperatures (10,12,22,31,33). To determine if A cells of E. coli O157:H7 sustained acid tolerance on BCT during refrigerated storage, an additional experiment was incorporated during the course of spray wash experiments with the acid-adaptable E. coli O157:H7 strain ATCC 43889.…”

“…In addition to promoting survival in low-pH foods, the development of acid resistance by E. coli O157:H7 may provide cross-protection against heat, salt, and irradiation preservation of foods (7,11,23,36). Furthermore, several works have indicated that acid tolerance of E. coli O157:H7 is enhanced or sustained longer upon refrigerated storage (10,12,22,31,33). Finally, it is thought that acid resistance and/or induction of acid tolerance may better enable pathogens to survive gastrointestinal acidity and ultimately cause disease and that it may enhance virulence (1,15,26,35).…”

Health and Safety Considerations of Fermented Sausages

“…Freezing of raw meat prior to be used in DFS production is not uncommon. Bacteria in the meat can be damaged by a freeze/thaw process, and this has been shown to provide an extra 0.5-1-log reduction of E. coli O157:H7 in the final salami product [213]. Another strategy, commercially used in the USA, is heat treatments of raw meat ingredients by lactic acid-hot water (80-90 ∘ C).…”

Quantification of the Relative Effects of Temperature, pH, and Water Activity on Inactivation of Escherichia coli in Fermented Meat by Meta-Analysis

“…However, pathogenic Escherichia coli can contaminate and survive in fermented meat products at levels sufficient to cause serious illness in consumers, as evidenced by numerous outbreaks of E. coli infections epidemiologically linked to uncooked fermented meat products (8,9,54,64). Knowledge of the kinetics of nonthermal inactivation of E. coli, and the factors affecting it, is important to be able to optimize the safety of fermented meat processes.Several research groups have conducted studies on the survival of pathogenic E. coli during the processing of specific fermented meat products (4,6,14,16,23,25). In some cases, the effects of alternative ingredients or processing parameters have also been determined (12,21,24,30).…”

“…Several research groups have conducted studies on the survival of pathogenic E. coli during the processing of specific fermented meat products (4,6,14,16,23,25). In some cases, the effects of alternative ingredients or processing parameters have also been determined (12,21,24,30).…”