Effects of Postharvest Handling Conditions on Internalization and Growth of Salmonella enterica in Tomatoes †

Salmonellainternalization in tomatoes during postharvest handling is a major food safety concern. This study was conducted to determine the effect of immersion time, immersion depth, and temperature differential between bacterial suspension and tomato pulp on the internalization of Salmonella entericain tomato fruits. The effect of storage temperature and duration on the survival and growth of internalized Salmonellacells was also evaluated. Overall, immersion time significantly affected the incidence and extent of S. entericainternalization (P< 0.0001), with a linear correlation between immersion time and Salmonellainternalization. The depth of Salmonellainternalization in tomato tissues also increased with increasing immersion time. Immersion time also significantly influenced the degree to which the temperature differential affected Salmonellainternalization. With an immersion time of 2 min, the temperature differential had no significant effect on Salmonellainternalization (P= 0.2536). However, with an immersion time of 15 min, a significantly larger Salmonellapopulation became internalized in tomatoes immersed in solutions with a −30°F (−16.7°C) temperature differential. Internalized S. entericacells persisted in the core tissues during 14 days of storage. Strain type and storage duration significantly affected (P< 0.05) both the frequency detected and the population of internalized Salmonellarecovered, but storage temperatures of 55 to 70°F (12.8 to 21.1°C) did not (P>0.05). These findings indicate the importance of preventing pathogen internalization during postharvest handling.