P2-06 Microbiological Growth Profile of Staphylococcus aureus and Bacillus cereus in Flour-based Batters during Routine Manufacturing Conditions

Tuesday, August 5, 2014
Exhibit Hall D (Indiana Convention Center)
Balasubrahmanyam Kottapalli, ConAgra Foods, Inc., Omaha, NE
Brad Ziebell, ConAgra Foods, Inc., Omaha, NE
Yanyan Huang, ConAgra Foods, Inc., Omaha, NE
Stefanie Gilbreth, ConAgra Foods, Inc., Omaha, NE
Steven Hermansky, ConAgra Foods, Inc., Omaha, NE
Introduction: Flour-based batter systems (aw > 0.91) used for bakery products may support the growth of Staphylococcus aureus and/or Bacillus cereus and, given favorable conditions, may produce heat stable enterotoxin during routine manufacturing.

Purpose: The purpose of this study was to evaluate the role of competitive inhibition and the microbiological growth profile of S. aureus and B. cereus in batters.

Methods: Batter samples were individually inoculated in triplicate with strains of S. aureus and B. cereus to achieve a target level of 102 to103 CFU/g. Following inoculation, samples were stored at 20 or 35°C and analyzed at several time points between 0 and 72 hours. Batter samples were analyzed for S. aureus, B. cereus, and lactic acid bacteria (LAB) using scientifically valid methods. In accordance with FDA published guidance, the food safety limit was defined as 105 CFU/g for S. aureus and 106 CFU/g for B. cereus.

Results: At a temperature of 20°C for 72 hours, neither S. aureus nor B. cereus reached the food safety limit. At a temperature of 35°C, both S. aureus and B. cereus reached the FDA prescribed limits of food safety around 16 hours.  However, both S. aureus and B. cereus decreased (P < 0.05) after 24 hours to below the FDA prescribed limits for food safety. The observed trends at both temperatures were attributed to the growth of naturally occurring LAB.

Significance: Data for S. aureus and B. cereus suggest the important role of ‘competitive inhibition’ from naturally occurring LAB at 20 and 35°C in flour-based batters.  The study findings indicate competitive inhibition resulted in no significant food safety risk at a temperature of 20°C and a reduction in S. aureus and B. cereus growth at 35°C. Further investigation of the toxigenic ability of these strains at 35°C is warranted. The data generated in this study provide scientific basis to support manufacturing processes for flour-based batters.