Viability of Escherichia coli O157:H7 in pepperoni during the manufacture of sticks and the subsequent storage of slices at 21, 4 and -20 degrees 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 10(8) cfu/g) and a five-strain cocktail of Escherichia coli O157:H7 (greater than or equal to 2 X 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 CO2 and stored at - 20, 4 and 21 degrees C. Sticks were fermented at 36 degrees C and 85% relative humidity (RH) to less than or equal to pH 4.8 and then dried at 13 degrees C and 65% RH to a moisture/protein ratio (M/Pr) of less than or equal to 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 degrees 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 degrees 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. (C) 1997 Elsevier Science B.V.