The combined effect of starter culture (107 CPU of lactic acid bacteria per ml), dextrose (0.8%), sodium chloride (2%), nitrite (200 ppm), and temperature (37 and 22°C) on survival of bioluminescent Escherichia coli O157:H7 (l00 to 105 CPU/ml) in brain heart infusion (BHI) broth was determined.
Two model systems representing fermented sausage production were evaluated. The first was the “American style” employing high-temperature (37°C) and short-time (1-day) fermentation. The second was the “European style” in which 22°C was used for 3 days. After fermentation, the samples were stored at 10°C and the survival of E. coli O157:H7 was monitored over an extended period of time.
In the “American style” model, E. coli O157:H7 survived a more than 34-day period in BHI containing starter culture and dextrose, while it survived for a more than 51-day period in BHI containing starter culture, dextrose, sodium chloride, and nitrite.
In the “European style” model, the survival time of E. coli O157:H7 during fermentation was longer in BHI containing starter culture and dextrose than in BHI containing starter culture, dextrose, sodium chloride, and nitrite. E. coli O157:H7 did not survive past 9 days in BHI containing starter culture and dextrose. Similarly, in BHI containing starter culture, dextrose, sodium chloride, and nitrite the lower E. coli O157:H7 inoculations (l00 to 104 CFU/ml) did not survive past 9 days; however, at higher inoculum levels (≥105 CFU/ml) the organism survived more than 30 days.
In conclusion, the lower temperature and longer fermentation time (“European style”) is better for elimination of E. coli O157:H7 from a model system representing a fermented sausage production than fermentation at high temperature and short time (“American style”).
Efficacy of compressed sodium chloride (CSC) against E. coli and Candida auris in minutes and methods improvement for testing