Viability of Escherichia coli O157:H7 during manufacturing and storage of a fermented, semidry soudjouk-style sausage.

Soudjouk-style batter was inoculated with a five-strain mixture of Escherichia coli O157:H7 at about 7.6 log10 CFU/g in each of two trials. The sticks were fermented and dried at 22 degrees C and 50% relative humidity (RH) for 3 days and then at 9 degrees C and 40% RH for 18 h. After being flattened to about 1.25 cm, the sticks were conditioned at 38 degrees C and 70% RH or at 22 degrees C and 50% RH for about 3 days. After the latter conditioning treatment, sticks either were cooked to an internal temperature of 63 degrees C or received no heat treatment. Final mean pH values after conditioning at 22 degrees C and 50% RH for soudjouk manufactured with a starter culture and dextrose (1.0%) and for soudjouk manufactured without a starter culture were about 4.9 and 6.0, respectively. For soudjouk produced with a starter culture, pathogen numbers were reduced by 4.53 and 0.88 log10 CFU/g after conditioning at 38 degrees C and 70% RH and at 22 degrees C and 50% RH, respectively. For soudjouk produced via natural fermentation, pathogen numbers were reduced by 1.39 and 0.09 log10 CFU/g after conditioning at 38 degrees C and 70% RH and at 22 degrees C and 50% RH, respectively. Cooking reduced pathogen numbers to below the levels detectable by direct plating (<1.0 log10 CFU/g) and by enrichment for soudjouk produced with a starter culture and also reduced pathogen numbers by 6.28 log10 CFU/g for soudjouk produced via natural fermentation. However, cooking also resulted in an unacceptable product. In general, the reduction in pathogen numbers achieved by storage at ambient temperature (25 degrees C) was greater than that achieved by storage at cooler temperatures (4 and 15 degrees C), particularly for soudjouk prepared with a starter culture (for which a final pH value of 4.8 and a 6.4-log10 reduction were obtained after 21 days at 25 degrees C) rather than for that prepared without a starter culture (for which a final pH value of 6.1 and a 2.6-log10 reduction were obtained after 21 days at 25 degrees C). These results indicate that naturally fermented old-country-type sausage may allow the survival of E. coli O157:H7 in the absence of controlled fermentation, postfermentation cooking, and/or an ambient-storage processing step.