Survival of Salmonella in Cookie and Cracker Sandwiches Containing Inoculated, Low-Water Activity Fillings

Introduction: Low-Water activity (a_w) fillings in cookie and cracker sandwiches have not been considered as likely vehicles of foodborne pathogens.  An outbreak of salmonellosis associated with a marshmallow confectionery and observations that Salmonella can survive for 8 months or more in fondant, halva, and dried fruits, however, have raised interest in learning more about its survival in high-sugar products.

Purpose: The purpose of this study was to determine the rate of inactivation of Salmonella in crème and non-crème fillings in cookies and cracker sandwiches.

Methods: Two types of cookies, crackers, and high-sugar fillings (a_w 0.18), along with peanut butter- and cheese-based fillings (a_w 0.25), were obtained from commercial sources.  Sandwiches containing fillings dry- or wet-inoculated with Salmonella at high and low levels were stored at 25°C for 1 and 6 days and for 3, 5, 10, 16, and 26 weeks.  Sandwiches were analyzed for populations and presence (by enrichment) of Salmonella.

Results: At initial populations of 3.4 and 3.6 log CFU/g of chocolate crème and peanut butter crème cookie sandwiches, Salmonella survived for at least 26 weeks; initially at 0.38 log CFU/g, the pathogen survived for 5 and 10 weeks, respectively.  Initially at 2.9 and 3.4 log CFU/g of cracker sandwiches containing peanut butter- and cheese-based fillings, respectively, Salmonella survived for 26 and 16 weeks; initially at 0.53 log CFU/g, the pathogen survived in cracker sandwiches containing peanut butter-based and cheese-based fillings for 6 days and 5 weeks, respectively.  Inactivation was more rapid in wet-inoculated peanut butter crème filling than in dry-inoculated filling but unaffected by type of inoculum in peanut butter-based filling.

Significance: The ability of Salmonella to survive for up to 26 weeks in cookie and cracker sandwiches demonstrates a need to assure that filling ingredients do not contain the pathogen and contamination does not occur during manufacture.