Validation of Pepperoni Processes for Control of Escherichia coli O157:H7

Abstract

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°F (53°C) for 60 min resulted in a ≥5-log unit decrease in numbers of strain O157:H7 without visibly affecting the texture or appearance of the product. These data revealed that a traditional nonthermal, process for pepperoni was only sufficient to eliminate relatively low levels (ca. 2 log CFU/g) of E. coli O157:H7, whereas heating to internal temperatures of 145°F (63°C) instantaneous or 128°F (53°C) for 60 min delivered a 5 to 6 log unit reduction in counts of the pathogen in pepperoni.

Effects of Acid Adaptation, Product pH, and Heating on Survival of Escherichia coli O157:H7 in Pepperoni

“…The data obtained in this study has, perhaps, greater utility than that from other studies (3,8,10), as it can be used by a manufacturer to identify an optimum heat treatment step which meets relevant product requirements, in terms of product safety, while maintaining other important sensory characteristics.…”

“…Other heating protocols have also been designed for this purpose (3,8,10). The heat treatments reported by these researchers as effective in these products are milder than the treatments identified as necessary in this study.…”

“…Information on the pattern of thermal inactivation of E. coli O157:H7 in pepperoni was applied in the development of heating processes designed to reduce E. coli O157:H7 numbers therein by 5 log 10 units.The identification of fermented meat as a vehicle of infection for Escherichia coli O157:H7 (4) has led to the development of heat treatments for such products (3,8,10) such that a 5-log 10 -unit reduction in E. coli O157:H7 numbers can be achieved during processing. Fermented meat had traditionally relied on its low pH status as its primary preservative mechanism; however, E. coli O157:H7 has been shown to be unusually resistant to inactivation at low pHs (9, 12, 13).…”

Elimination ofEscherichia coliO157:H7 from Fermented Dry Sausages at an Organoleptically Acceptable Level of Microencapsulated Allyl Isothiocyanate

“…The ability of E. coli O157:H7 to adapt to acid environments (11) has caused this microorganism to be regarded as one of the most dangerous pathogens in fermented meat products. Several studies have shown that E. coli O157:H7 is able to survive the processes of fermentation, drying, and storage when this microorganism is present at high numbers (14,16,27). The use of different starter cultures during fermentation has been unsuccessful in achieving the required 5-log 10 -unit reduction of E. coli O157:H7 (12,22).…”

“…The use of different starter cultures during fermentation has been unsuccessful in achieving the required 5-log 10 -unit reduction of E. coli O157:H7 (12,22). Heat treatments seem to be the best way to reduce the numbers of this pathogen in semidry sausages; however, physical characteristics of dry sausage change during heating, and the products no longer resemble uncooked fermented sausages (16).…”