Purpose: To monitor the survival of three pathogenic bacteria during storage of fermented table olives, approaching the cross-contamination scenario during the packaging process of olives.
Methods: Τhe survival of Escherichia coli O157:H7, Salmonella Enteritidis and Listeria monocytogeneswas studied during the storage of fermented green table olives in brine at 20°C, and fermented black table olives in air at 4 and 20°C. Each pathogen was tested as a mixed culture (3 or 5 strains of each pathogen were used for black or green olives, respectively).
Results: In green olives packed in brine, the population of E. coli O157:H7 and S. Enteritidis was reduced gradually and detected until the 19th and 27th day of storage, respectively, while L. monocytogenes could be detected until the end of storage period (48 days). The population of all pathogens in aerobically packed black olives showed a remarkable decrease below the detection limit after the first day of storage, at both storage temperatures. E. coli O157:H7 and S. Enteritidis could not be detected after 5 and 6 days of storage, respectively, at both temperatures. The population of L. monocytogenescould not be detected after the 6th day of storage at 20°C, but almost all samples at 4°C were found enrichment positive at the end of storage.
Significance: The results showed that successfully fermented table olives generally do not support the growth of pathogens. However, the adaptation and survival of pathogens is possible and for this reason risk-assessment studies and application of strictly good manufacturing practices are needed to reduce the possibility of cross contamination.