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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Publications at this Location » Publication #295829

Title: Effects of post-harvest handling conditions on internalization and growth of Salmonella enterica in tomatoes

item ZHOU, BIN - University Of Maryland
item Luo, Yaguang - Sunny
item Nou, Xiangwu
item YANG, YANG - University Of Maryland
item WU, YUNPENG - University Of Maryland
item WANG, QI - University Of Maryland

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2013
Publication Date: 3/1/2014
Publication URL:
Citation: Zhou, B., Luo, Y., Nou, X., Yang, Y., Wu, Y., Wang, Q. 2014. Effects of post-harvest handling conditions on internalization and growth of Salmonella enterica in tomatoes. Journal of Food Protection. 77:365-370.

Interpretive Summary: Infiltration of pathogenic bacteria into the internal tissues of tomatoes during packing house operation is a major food safety concern. A comprehensive study was conducted to evaluate the internalization of Salmonella enterica, a human pathogen previously associated with tomato outbreaks, as affected by typical tomato wash tank operation conditions. In addition, its survival and growth in tomatoes as affected by storage temperature and duration was also assesed. These studies demonstrate that shortening tomato immersion time in wash tank can significantly reduce bacterial internalization. This research provides critical information to the FDA and the tomato industry for developing science-based preventative control measures to improve tomato food safety.

Technical Abstract: Internalization during post-harvest handling is a significant route of tomato contamination by phytopathogens and foodborne human pathogens. This study was conducted to determine the effect of immersion time, immersion depth, and the temperature differential between bacterial suspension and tomato pulp on the internalization of Salmonella enterica in tomato fruits. The effect of storage temperature and duration on the survival and growth of internalized Salmonella cells was also evaluated. Overall, immersion time significantly affected the incidence and extent of S. enterica internalization, with a linear correlation between immersion time and Salmonella internalization. The depth of Salmonella internalization in tomato tissues also increased with increasing in immersion time. Immersion time also affects of the effect of temperature differential on Salmonella internalization. With immersion time of 2 min, temperature differential had no significant effect on Salmonella internalization. However, with immersion time of 15 min, a significantly larger Salmonella population internalized tomatoes immersed in solutions with a -30 oF temperature differential. Internalized S. enterica cells persisted in the core tissues during a 14 day storage. Both the frequency and population size of Salmonella internalization was significantly affected by strain type and storage duration, but not by storage temperature (55 and 75 °F). These findings underline the importance of preventing pathogen internalization during post harvest handling.