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Research Project: Characterization and Mitigation of Bacterial Pathogens in the Fresh Produce Production and Processing Continuum

Location: Environmental Microbial & Food Safety Laboratory

Title: Internalization of Listeria monocytogenes in cantaloupes during dump tank washing and hydrocooling

Author
item MACARISIN, DUMITRU - Food And Drug Administration(FDA)
item WOOTEN, ANNA - Food And Drug Administration(FDA)
item DE JESUS, ANTONIO - Food And Drug Administration(FDA)
item HUR, MINJI - Food And Drug Administration(FDA)
item BAE, SEONJAE - Food And Drug Administration(FDA)
item Patel, Jitu
item EVANS, PETER - Food And Drug Administration(FDA)
item BROWN, ERIC - Food And Drug Administration(FDA)
item HAMMACK, THOMAS - Food And Drug Administration(FDA)
item CHEN, YI - Food And Drug Administration(FDA)

Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2017
Publication Date: 6/19/2017
Citation: Macarisin, D., Wooten, A., De Jesus, A., Hur, M., Bae, S., Patel, J.R., Evans, P., Brown, E., Hammack, T., Chen, Y. 2017. Internalization of Listeria monocytogenes in cantaloupes during dump tank washing and hydrocooling. International Journal of Food Microbiology. 527:165-175.

Interpretive Summary: Recent listeriosis outbreaks and recalls associated with cantaloupes urge for studies to understand the mechanisms of cantaloupe contamination by Listeria monocytogenes. Current postharvest practices such as washing and hydrocooling could facilitate contamination of cantaloupes by human pathogens. We investigated the potential for L. monocytogenes internalization into cantaloupes during dump tank washing and immersion-type hydrocooling in water contaminated with L. monocytogenes. The effect of cantaloupe variety, water temperature, and harvesting technique on L. monocytogenes internalization was also evaluated. L. monocytogenes infiltrated both full slip and clipped cantaloupes through the stems, and was then distributed along the vascular system through the edible portion of the cantaloupe via secondary vascular bundles. The internalization of L. monocytogenes was significantly affected by harvesting technique of cantaloupes (clipped vs full slip) but not by water temperature or cantaloupe variety. The current study demonstrates that L. monocytogenes can internalize into warm cantaloupes during immersion in contaminated cold water. The research findings benefit produce processing industries.

Technical Abstract: Recent listeriosis outbreaks and recalls associated with cantaloupes urge for studies to understand the mechanisms of cantaloupe contamination by Listeria monocytogenes. Postharvest practices such as washing and hydrocooling were suggested to facilitate the contamination of fresh fruits by human pathogens. This study assessed the potential for L. monocytogenes internalization into cantaloupes during dump tank washing and immersion-type hydrocooling in water contaminated with L. monocytogenes. The effect of cantaloupe variety, water temperature, and harvesting technique on L. monocytogenes internalization was also evaluated. Full slip Western and Eastern cantaloupes were pre-warmed to 42°C and then immersed in water at 6°C and 18°C containing 4 and 6 log CFU/ml of L. monocytogenes. Clipped Western and Eastern cantaloupes were pre-warmed to 42°C and then immersed in water at 6°C containing 6 log CFU/ml of L. monocytogenes. Water containing L. monocytogenes infiltrated both full slip and clipped cantaloupes through the stems/stem scars and was then distributed along the vascular system in hypodermal mesocarp reaching the calyx area of the fruit. Water influx spread through the middle-mesocarp (edible portion of the cantaloupe) via secondary (smaller) vascular bundles. The current study demonstrated that, under experimental conditions, L. monocytogenes can internalize into warm cantaloupes during immersion in cool water contaminated by L. monocytogenes. The incidence and levels of L. monocytogenes internalized in the middle-mesocarp were not significantly affected by water temperature or cantaloupe variety. Significantly lower incidence and numbers of internalized L. monocytogenes were detected in clipped than in full slip cantaloupes.