Purpose: This study was conducted to determine the effect of immersion time and temperature differential between tomato pulp and wash solution on the internalization of S. entericain tomatoes, and its distribution once internalized.
Methods: Freshly harvested mature green tomatoes held at 90°F (32.2°C) were immersed in water containing approximately 100,000 CFU/ml S. enterica Newport. Tomato variety (cv. BHN602 and Sun Bright), temperature differential (-30, -10, 0, 10°F) between tomato pulp and the inoculated wash solution, and immersion time (2, 5, 10, 15 min) were evaluated for their effects on S. enterica internalization, as well as the effects of these postharvest handling conditions on the infiltration depth. The incidence and cell populations were determined via culture enrichment and most probable number methods, respectively.
Results: The incidence and extent of S. enterica internalization was significantly impacted by the range of temperature differential and immersion time and their interactions. Significantly more severe pathogen internalization was observed with a 15-min immersion time than a 2-min immersion time. With a 15-min immersion time, significantly more pathogen internalization was observed with temperature differentials of -10 and -30°F than with temperature differentials of 0 and 10°F. However, with a 2-min immersion time, no significant difference for pathogen internalization was observed among the temperature differentials of 10 to -30°F under the testing conditions.
Significance: This study provides critical information for the tomato industry and the FDA to develop science-based food safety regulations and guidelines to prevent pathogen internalization.