Validation of Baking of White Chocolate Chip Macadamia Nut Cookie Dough

Introduction: In 2009, flour was implicated in the E. coli O157:H7 outbreak in frozen cookie dough.  More recently, macadamia nuts have been recalled due to Salmonella contamination.  White chocolate chip macadamia nut (WCCMN) cookie dough, containing relatively large or dense chips and macadamia nut pieces, may pose a challenge from a thermal processing standpoint should an ingredient be contaminated.  While baked products are generally perceived as microbiologically safe, a FSMA-compliant Food Safety Plan should include data showing that baking yields an appropriate log reduction.

Purpose: The purpose was to determine the log reduction of three specific pathogens in inoculated WCCMN cookie dough after baking.

Methods: Dough samples were individually inoculated with strains of Salmonella, Listeria monocytogenes, and E. coli O157:H7 to achieve target levels of 10⁶ to 10⁷ CFU/g.  Following inoculation, samples were baked at 350°F for 7.5 minutes.  After baking, each cookie was analyzed to determine the log reduction for each pathogen. 

Results: In WCCMN cookies inoculated with Salmonella, Listeria monocytogenes, and E. coli O157:H7 a minimum 4-log reduction was achieved.  For each pathogen category, two trials were conducted on separate days.  Each trial consisted of three baking replications of two test cookies for twelve results for each pathogen. 

Significance: These data suggest WCCMN cookies (of a specified size) are not a microbiological food safety risk when baked for 7.5 minutes in a 350°F oven.  Generally, the FDA uses a minimum 5-log reduction for food safety.  However, an internal risk assessment on macadamia nuts determined 4 logs to be adequate, and prevalence data for flour show that contamination levels for pathogens is very low.  Purchasing pre-treated nuts or flour is not necessary to ensure food safety as long as these minimum baking parameters are achieved.