P2-05 Effect of Thermal Processing on the Survival of Salmonella spp., Listeria monocytogenes and Escherichia coli O157:H7 during the Baking of Pretzels and Pita Chips

Tuesday, August 5, 2014
Exhibit Hall D (Indiana Convention Center)
Balasubrahmanyam Kottapalli, ConAgra Foods, Inc., Omaha, NE
Denise Becker, ConAgra Foods, Inc., Omaha, NE
Yanyan Huang, ConAgra Foods, Inc., Omaha, NE
Michael Meyer, ConAgra Foods, Inc., Omaha, NE
Stefanie Gilbreth, ConAgra Foods, Inc., Omaha, NE
Steven Hermansky, ConAgra Foods, Inc., Omaha, NE
Introduction: Recent recalls and outbreaks due to foodborne pathogens in thermally processed low moisture foods highlight the need for food industries to validate their thermal process.

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.