Viability of Escherichia coli O157:H7 in pepperoni during the manufacture of sticks and the subsequent storage of slices at 21, 4 and −20 ° C under air, vacuum and CO2

A raw, pepperoni batter (75% pork:25% beef with a fat content of about 32%) was inoculated with a pediococcal starter culture (about 108 cfug) and a five-strain cocktail of Escherichia coli O157:H7 (≥ 2 × 107 cfug), mixed with non-meat ingredients, and then hand-stuffed into 55 mm fibrous casings to form sticks. The numbers of the pathogen were determined before stuffing, after fermentation, after drying/slicing, and after periods of storage. For storage, slices were packaged under air, vacuum or CO2 and stored at − 20, 4 and 21 °C. Sticks were fermented at 36 °C and 85% relative humidity (RH) to ≤ pH 4.8 and then dried at 13 °C and 65% RH to a moistureprotein ratio (MPr) of ≤ 1.6:1. Fermentation and drying resulted in the numbers of the pathogen decreasing by about 2 log10 units. During storage, the temperature rather than the atmosphere had the greater effect on pathogen numbers. The greatest reductions in numbers were observed during storage at 21 °C, when numbers decreased to about 2 and 3.8 log10 cfug within 14 days in product stored under air and vacuum, respectively, and a 5 log10 reduction was observed for both atmospheres within 28 days. Regardless of the storage atmosphere, numbers did not decrease below 3.6 or 3.7 log10 cfug after 90 days of storage at −20 or 4 °C, respectively. These data confirm that fermentation and drying are sufficient to eliminate only about 2 log10 cfug of E. coli O157:H7 from fermented sausage, and that additional strategies, such as storage for at least 2 weeks at ambient temperature in air, are required to achieve a 5 to 6 log10 reduction in the numbers of the pathogen in sliced pepperoni.