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 CO 2

Abstract

A raw, pepperoni batter (75% pork:25% beef with a fat content of about 32%) was inoculated with a pediococcal starter culture (about 10 8 cfu g ) and a five-strain cocktail of Escherichia coli O157:H7 (≥ 2 × 10 7 cfu g ), 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 CO 2 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 moisture protein ratio ( M Pr ) of ≤ 1.6:1. Fermentation and drying resulted in the numbers of the pathogen decreasing by about 2 log 10 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 log 10 cfu g within 14 days in product stored under air and vacuum, respectively, and a 5 log 10 reduction was observed for both atmospheres within 28 days. Regardless of the storage atmosphere, numbers did not decrease below 3.6 or 3.7 log 10 cfu g 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 log 10 cfu g 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 log 10 reduction in the numbers of the pathogen in sliced pepperoni.