Purpose: This project evaluated the effect of storage duration and temperature on the survival and growth of Salmonella cells internalized through infiltration during simulated tomato dump tank handling.
Methods: Green mature tomatoes were inoculated with Salmonella enterica, including S. Newport, S. Typhimurium, and S. Thompson. Batches of tomatoes (90°F) were submerged in cell suspensions (80°F) of individual Salmonella strains for 15 min, treated with surface disinfectant and stored at 54°F and 70°F for up to two weeks. Samples of the core tissue (11mm x 15mm disc, 20mm below stem scar surface) were excised on days 0, 7, and 14 to enumerate Salmonella cells infiltrating and surviving inside tomato tissues using a microplate MPN.
Results: The frequency of Salmonella presence in the core tissues was significantly affected by strain type (P < 0.05) and storage time (P < 0.05). The cell populations for selected strains of S. Thompson and S. Typhimurium in tomato core tissue increased by 1.71 and 3.65 log MPN/g after the storage for 14 days, respectively. This indicated a significant proliferation by certain strains in tomato tissues during the storage. The increase in cell counts was significantly affected by strain type (P < 0.0001) and storage time (P < 0.0001). Although the tested strains responded to the storage differently, they were all capable of survival and even proliferated in the ripening tomato tissues.
Significance: These findings underline the importance of preventing pathogen infiltration during post-harvest processing.