Recent Foundation Research Findings
Validation of lethality and stabilization processes for products with slow come up time: bacon and bone-in ham, Iowa State University, University of Wisconsin, HansonTech

Research determined the effect of slow come-up time and slow stabilization during the thermal processing of bacon and bone-in ham on the survival of Clostridium perfringens, Staphylococcus aureus, Listeria monocytogenes and Salmonella spp.

Ten cured-ham treatments were formulated to represent ranges of 55-75% moisture, pH 5.8-6.4, and 1.5-3.0% salt using a full factorial design. Raw treatments were inoculated with 3-log CFU/g Listeria monocytogenes, Staphylococcus aureus, Salmonella spp., or Clostridium perfringens spores and vacuum packaged.  Samples were heated according to Appendix A (in 6 hours) or slow-cook (in 10 hours), and then continued heating until internal temperature of 70°C.  Samples were slow cooled from 54 to 4°C in 25 hours (extended from Appendix B).  Duplicate samples per treatment were assayed at 0-time and at internal temperatures 32, 54, 70, 54, 29, and 4°C by enumerating on appropriate selective agars.

All treatments inoculated with L. monocytogenes, S. aureus, Salmonella spp. or C. perfringens inhibited growth during control and slow cook.  All three vegetative pathogens were inactivated by cooking to 70°C.  No difference in survival was observed between Appendix A and slow-cook treatments.  In contrast, C. perfringens increased 4.7, 3.0, and 1.7 log during the 25-h extended cooling in 75% moisture treatments with pH 6.4/1.5% NaCl, pH 6.4/3.0% NaCl and pH 5.8/1.5% NaCl, respectively.  In addition, 55% moisture ham with pH 6.4 and 6.1 and low salt supported a >1.5 log increase.  None of the other treatments supported growth during the 25-h extended cool.

This study confirms the critical nature of salt, pH and moisture for pathogen inhibition in cured meat during extended dwell times.

The article and others are available in the January 2019 Foundation Focus Newsletter