Tracking diarrheagenic Escherichia coli throughout mozzarella cheese production: Identification of critical control points and sanitation gaps

Escherichia coli in food indicates fecal contamination, and certain strains may compromise food safety, such as diarrheagenic strains (DEC). This study aimed to track the presence of DEC throughout mozzarella production and identify postpasteurization critical control points. The E. coli counts and DEC characterization were performed across different batches of mozzarella, from raw milk to the final 120 d of shelf life. Among the 58 isolates collected from raw milk, 15.52%, 8.62%, and 3.35% were identified as enteropathogenic (EPEC), enteroaggregative (EAEC), and enteroinvasive E. coli, respectively. Pasteurization significantly affected (P < 0.05), reducing E. coli counts to undetectable levels and eliminating all DEC isolates. Nonetheless, during the coagulation step, which immediately follows pasteurization, the median count rose to 2 (±1.51) log cfu/mL, and both EPEC and EAEC were detected. These same pathotypes remained detectable after fermentation, with counts increasing to 3.3 (±0.55) log cfu/mL. From the stretching and brining stages onward, no DEC strains were detected, and only nonpathogenic E. coli isolates remained. By the end of the shelf-life period, no E. coli isolates were recovered. Although various stages of mozzarella cheese production contributed to reducing E. coli counts and DEC presence, pasteurization remains the only critical control point that is sufficiently effective in ensuring the microbiological safety of mozzarella. Furthermore, the results suggest that the coagulation vats may represent a critical point for fecal contamination in mozzarella production. These findings emphasize the need for strengthened postpasteurization hygiene protocols to ensure mozzarella safety.