| In objective one, the thermal inactivation kinetics of E. coli O157:H7 and C. jejuni on vacuum-packaged bologna slices were determined Samples were submerged in a pre-heated water bath and survivors determined at selected time intervals. D-values for E. coli O157:H7 at 55°, 60°, 65°, 70°C and 75°C were 289.5, 45.8, 15.8, 11.9 and 9.1 seconds, respectively (zD-value = 13.9°C). D-values for C. jejuni at 53°, 55°, 60°, and 62°C were 272.0, 192.1, 38.4, and 25.2 seconds, respectively (zD-value = 83°C).; In objective two, the inhibitory activity of wheat gluten and glycerol-based films containing nisin, chelators, and a surfactant (Film+N) were evaluated against these same pathogens suspended in peptone water. Control treatments of wheat gluten/glycerol films (Film) and no films were also tested. E. coli populations increased 3-logs over the 72 h exposure period for the Control and Film treatments whereas the Film+N populations decreased 2-logs. C. jejuni populations decreased to below the detectable level after 24h exposure to all three treatments.; In objective three, the inoculated bologna samples were subjected to a minimal in-package pasteurization process combined with the two film treatments and then stored at 4°C for 7 days (both organisms) and 5 weeks ( E. coli). Minimal reductions in E. coli populations of 1.0, 0.5, and 0.35 log cfu/ml were detected across the Control, Film and Film+N treatments, respectively, following 7 days. E. coli populations declined by 1.74, 1.14 and 0.27 log cfu/ml, respectively, following 5 weeks. C. jejuni, populations declined by 1.51, 2.11, and 2.68 log cfu/ml for the Control, Film and Film+N treatments, respectively. In summary, the nisin-containing films were more inhibitory against these pathogens in a liquid system as opposed to the ready-to-eat turkey bologna. |
