SURVIVAL OF ESCHERICHIA-COLI O157-H7 IN FULL-AND REDUCED-FAT PEPPERONI AFTER MANUFACTURE OF STICKS, STORAGE OF SLICES AT 4-DEGREES-C OR 21-DEGREES-C UNDER AIR AND VACUUM, AND BAKING OF SLICES ON FROZEN PIZZA AT 135, 191 AND 246-DEGREES-C

Pepperoni batter was prepared with fat contents of about 15, 20, and 3 2% (wt/wt) and inoculated with a pediococcal starter culture and great er than or equal to 2.0 x 10(7) CFU/g of a five-strain inoculum of Esc herichia coli O157:H7. The batter was fermented at 96 degrees F (ca. 3 6 degrees C) and 85% relative humidity (RH) to pH less than or equal t o 4.8 and then dried at 55 degrees F (ca. 13 degrees C) and 65% RH to a moisture/protein ratio of less than or equal to 1.6:1. For storage, slices were packaged under air or vacuum and stored at 39 degrees F (c a. 4 degrees C) and 70 degrees F (ca. 21 degrees C). For baking, froze n slices were placed on retail frozen cheese pizzas that were subseque ntly baked at 275 degrees F (ca. 135 degrees C), 375 degrees F (ca. 19 1 degrees C), or 475 degrees F (ca. 246 degrees C) for 0 to 20 min. Ap preciable differences related to fat levels were observed after drying ; pathogen numbers decreased by 1.04, 1.31 and 1.62 log(10) units in s ticks prepared from batter at initial fat levels of 15, 20, and 32%, r espectively. During storage, the temperature rather than the atmospher e had the greater effect on pathogen numbers, with similar viability o bserved among the three fat levels tested. At 70 degrees F (ca. 21 deg rees C), compared to original levels, pathogen numbers decreased by gr eater than or equal to 5.56 and greater than or equal to 4.53 log(10) units within 14 days in slices stored under air and vacuum, respective ly, whereas at 39 degrees F (ca. 4 degrees C) numbers decreased by les s than or equal to 2.43 log(10) CFU/g after 60 days of storage under e ither atmosphere. Baking, as expected, resulted in greater reductions in pathogen numbers as the temperature and/or time of baking increased . However, it was still possible to recover the pathogen by enrichment after baking frozen slices on frozen pizza at 475 degrees F (ca. 246 degrees C) for 10 min or at 375 degrees F (ca. 191 degrees C) for 15 m in. The calculated D values for all three temperatures tested increase d as the fat content of the batter increased from 15 to 20 to 32%. The present study confirmed that fermentation and drying were sufficient to reduce levels of E. coli O157:H7 in pepperoni sticks by <2.0 log(10 ) CFU/g. Storage of slices for at least 14 days at ambient temperature under air resulted in a >5.5-log(10)-unit total reduction of the path ogen. Baking slices on frozen pizza for at least 15 min at 475 degrees F (ca. 246 degrees C) or 20 min at 375 degrees F (ca, 191 degrees C) was necessary to reduce pathogen numbers to below detection by both di rect plating and enrichment.