Survival of Foodborne Pathogens in Commercial Ready-to-Bake Raw Cookie Dough in Two Different Storage Conditions

Introduction: Since the multistate outbreak of Escherichia coli O157:H7 in 2009 associated with commercial ready-to-bake cookie dough, cookie dough is considered as a novel vehicle for transmission of Shiga toxin-producing E. coli. Additionally, use of raw eggs, a common source of Salmonella, as an ingredient increases the food safety risk associated with cookie dough.

Purpose: The purpose of this study was to examine the survival rate of two foodborne pathogens, Salmonella serovar Enteritidis and E. coli O157:H7 in commercial raw cookie dough during its storage.

Methods: Cookie dough samples were inoculated with 6.3 log CFU/g and 6.0 log CFU/g of Salmonella Enteritidis and E. coliO157:H7, respectively, and stored for 8 weeks at 4°C or  -18°C. Samples (20 g) were taken immediately after inoculation, and then every 2 to 4 days for plate counting.     

Results: During the 8 week-storage, 2.42 log reduction and 2.35 log reduction were observed at 4°C and -18°C, respectively, for Salmonella Enteritidis. For E. coliO157:H7, 2.23 log reduction and 1.99 log reduction were observed at 4°C and -18°C, respectively. This study indicates, even with a low moisture and high sugar content, pathogens can survive in cookie dough products stored under refrigeration or freezing, the conditions recommended by manufacturers, for more than 2 month.

Significance: The results suggest the prevention of pathogen contamination of cookie dough by good manufacturing practices and effective monitoring system would be the best way to prevent foodborne illnesses associated with cookie dough products. Also, it is strongly advised for consumers not to consume raw cookie dough as pathogens, if present in cookie dough, would not be easily eliminated during storage.