Purpose: The purpose of this study was to evaluate the microbiological growth profile of S. aureus and B. cereus in dough systems.
Methods: Dough samples were individually inoculated in triplicate with strains of S. aureus or B. cereus to achieve a target level of 102 to103 CFU/g. Following inoculation, samples were stored at 25 or 30 or 35°C and analyzed at several time points between 0 and 24 h. Dough samples were analyzed for S. aureus or B. cereus, lactic acid bacteria (LAB), yeast, pH and water activity using scientifically valid methods. In accordance with FDA published guidance, the limit of food safety was defined as 105 CFU/g for S. aureus and 106 CFU/g for B. cereus.
Results: At all of the evaluated temperatures, neither S. aureus nor B. cereus reached the food safety limit. S. aureus populations significantly (P < 0.05) decreased during the storage time while B. cereus populations declined and remained stable following 18 h of storage. The observed trends at all the temperatures may be attributed to the growth of LAB and yeast populations added as a part of the dough formulation. Water activity did not change (P > 0.05) during storage. pH significantly (P < 0.05) decreased with increase in LAB populations.
Significance: Data for S. aureus and B. cereus suggest the important role of ‘competitive inhibition’ from LAB and yeasts at 25, 30 or 35°C in dough based systems. The study findings indicate competitive inhibition resulted in no significant food safety risk at all of the evaluated temperatures and storage times. The data generated in this study provide scientific basis to support manufacturing processes for artisan bread dough manufacturing systems.