Lethality of Commercial Whole-Muscle Beef Jerky Manufacturing Processes against Salmonella Serovars and Escherichia coli O157:H7

Abstract

Thermal processes used in making whole-muscle beef jerky include a drying step, which may result in enhanced pathogen thermotolerance and evaporative cooling that reduce process lethality. Several salmonellosis outbreaks have been associated with beef jerky. In this study, a standardized process was used to inoculate beef strips with five-strain cocktails of either Salmonella serovars or Escherichia coli O157:H7, to marinate the strips at pH 5.3 for 22 to 24 h at 5°C, and to convert the strips to jerky using various heating and drying regimes. Numbers of surviving organisms were determined during and after heating and drying. Salmonella reductions of ≥6.4 log CFU and similar reductions in E. coli O157:H7 were best achieved by ensuring that high wet-bulb temperatures were reached and maintained early in the process (51.7 or 54.4°C for 60 min, 57.2°C for 30 min, or 60°C for 10 min) followed by drying at 76.7°C (dry-bulb temperature). Processes with less lethality that reduced counts of both pathogens by ≥5.0 log CFU were (i) heating and drying at 76.7°C (dry bulb) within 90 min of beginning the process, (ii) heating for successive hourly intervals at 48.9, 54.4, 60, and 76.7°C (dry bulb), and (iii) heating at 51.7°C (dry bulb) and then drying at 76.7°C (dry bulb), starting before the product water activity dropped below 0.86. In several trials, separate beef strips were inoculated with a commercial Pediococcus acidilactici starter culture as a potential surrogate for evaluating pathogen thermotolerance. The results of these trials suggested that this experimental approach may be useful for in-plant validation of process lethality.