Purpose: The objective of this study was to evaluate microbiological safety of commercial ready-to-bake cookie dough products by studying prevalence of indicator bacteria and pathogens in these products.
Methods: Chocolate chip cookie dough products of three different brands were purchased from retail stores, and analyzed for the presence of coliform, generic Escherichia coli, Salmonella and STEC. Petrifilm was used to determine the presence of coliform and E. coli, and multiplex PCR for invA gene and stx1/stx 2 genes were used for detection of Salmonella and STEC.
Results: Out of 90 samples tested, 7 samples contained detectable coliforms with counts ranging from 30 to 250 CFU/g, and only 2 samples contained generic E. coli at the level of higher than 10 CFU/g, which is the tolerance limit for refrigerated cookie dough products. Interestingly, 86% of coliform and 100% of E. coli were detected in products from two brands. Neither Salmonella nor E. coli O157:H7 were detected in any of the tested samples. It was noted that 96.7% and 97.8% of the tested cookie dough samples were within standards required by the regulation for coliform and E. coli, respectively. Additionally, even though all tested product samples were analyzed before their best by dates, prevalence of coliform and E. colicounts showed significant positive correlation with the storage time.
Significance: These results suggest the microbiological risk of cookie dough products could increase with longer storage time. The results also indicate the brands, or more precisely, ingredients and/or the entire manufacturing process of each brand could have correlation with microbiological risks of the final products.