John B. Luchansky

Cheddar cheese was prepared with Lactococcus lactis subsp. lactis MM217, a starter culture which contains pMC117 coding for pediocin PA-1. About 75 liters of pasteurized milk (containing ca. 3.6% fat) was inoculated with strain MM217 (ca. 10 ⁶ CFU per ml) and a mixture of three Listeria monocytogenes strains (ca. 10 ³ CFU per ml). The viability of the pathogen and the activity of pediocin in the cheese were monitored at appropriate intervals throughout the manufacturing process and during ripening at 8°C for 6 months. In control cheese made with the isogenic, non-pediocin-producing starter culture L. lactis subsp. lactis MM210, the counts of the pathogen increased to about 10 ⁷ CFU per g after 2 weeks of ripening and then gradually decreased to about 10 ³ CFU per g after 6 months. In the experimental cheese made with strain MM217, the counts of L. monocytogenes decreased to 10 ² CFU per g within 1 week of ripening and then decreased to about 10 CFU per g within 3 months. The average titer of pediocin in the experimental cheese decreased from approximately 64,000 arbitrary units (AU) per g after 1 day to 2,000 AU per g after 6 months. No pediocin activity (L. monocytogenes .

Pepperoni batter was prepared with fat contents of about 15, 20, and 32% (wt/wt) and inoculated with a pediococcal starter culture and ≥2.0 × 107 CFU/g of a five-strain inoculum of Escherichia coli O157:H7. The batter was fermented at 96°F (ca. 36°C) and 85% relative humidity (RH) to pH ≤ 4.8 and then dried at 55°F (ca. 13°C) and 65% RH to a moisture/protein ratio of ≤1.6:1. For storage, slices were packaged under air or vacuum and stored at 39°F (ca. 4°C) and 70°F (ca. 21°C). For baking, frozen slices were placed on retail frozen cheese pizzas that were subsequently baked at 275°F (ca. 135°C), 375°F (ca. 191°C), or 475°F (ca. 246°C) for 0 to 20 min. Appreciable differences related to fat levels were observed after drying; pathogen numbers decreased by 1.04, 1.31 and 1.62 log10 units in sticks prepared from batter at initial fat levels of 15, 20, and 32%, respectively. During storage, the temperature rather than the atmosphere had the greater effect on pathogen numbers, with similar viability observed amo...

The fate of Escherichia coli O157:H7 was monitored in salami during conditioning of batter, fermentation and drying of sticks, and storage of slices. The raw batter (75% pork:25% beef, wt/wt, fat c...

The outbreak of Escherichia coli O157:H7 linked with dry-cured salami in late 1994 prompted regulatory action that required manufacturers of fermented products to demonstrate a 5-log unit reduction in counts of this pathogen during processing. Therefore, pepperoni batter (75% pork:25% beef with a fat content of ca. 32%) was inoculated with a pediococcal starter culture and a five-strain mixture of E. coli O157:H7 (≥2 × 107 CFU/g) and stuffed into 55-mm diameter fibrous casings 47 cm in length. The viability of the pathogen was monitored before stuffing, after fermentation, after thermal processing, and/or after drying. Chubs were fermented at 96°F (36°C) and 85% relative humidity (RH) to pH ≤ 5.0 and then dried at 55°F (13°C) and 65% RH to a moisture/protein ratio of ≤1.6:1 (modified method 6 process). Counts of the pathogen decreased about 1.2 log units after fermentation and drying. In subsequent experiments, heating chubs after fermentation to internal temperatures of 145°F (63°C) instantaneous or 128°...