Purpose: The purpose of this study was to evaluate the thermal inactivation kinetics of Salmonella spp., Listeria monocytogenes, and Escherichia coli O157:H7 during the baking of pretzel and pita chips.
Methods: Four dough types with varying water activities (0.88-0.99) were inoculated with Salmonella spp. and Listeria monocytogenes in separate trials and baked at 300°F and 350°F for 5 to 30 minutes. Least squares regression was used to estimate the baking parameters required to achieve a minimum of 5-log reduction in Salmonella spp. and L. monocytogenes. These baking parameters were then used to challenge dough samples inoculated with E. coli O157: H7. All the experiments constituted 3 replicates. Samples inoculated with Salmonella spp., L. monocytogenes, and E. coliO157:H7 were enumerated using scientifically valid methods. Samples were also analyzed for water activity.
Results: Modeling of pretzel and pita chips data indicated that the thermal processing parameters required for a minimum of 5-log reduction in Salmonella spp., L. monocytogenes, and E. coli O157:H7 during baking were 350°F (hot air temperature) for 19.6 minutes. Water activities ranging from 0.605 – 0.927 and product temperatures ranging from 192 - 230°F were found to be the corresponding food safety verification parameters. The adjusted R-square values ranged from 0.78-0.99 (P< 0.05).
Significance: The study findings provide scientific basis that the thermal process employed by ConAgra Foods bakery manufacturing facilities achieves an acceptable lethality of vegetative pathogens from a food safety standpoint. Because this study indicates that production of a saleable product will result in achievement of adequate food safety parameters, this work supports the management of baking as an operational pre-requisite program (not a CCP) in a facility’s food safety plan.