Evaluating the potential for contamination of leafy greens with Listeria when using retrofitted washing machines

Abstract A large portion of foodborne outbreaks are associated with leafy greens, including by the pathogen Listeria monocytogenes. Small and medium-sized leafy green growers commonly retrofit washing machines to dry triple-washed leaves, utilizing their spin cycle. The potential for this practice t...

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Bibliographic Details
Main Authors: Pragathi Kamarasu, Lynne McLandsborough, Matthew D. Moore, Amanda J. Kinchla
Format: Article
Language:English
Published: Nature Portfolio 2025-07-01
Series:npj Science of Food
Online Access:https://doi.org/10.1038/s41538-025-00489-6
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Summary:Abstract A large portion of foodborne outbreaks are associated with leafy greens, including by the pathogen Listeria monocytogenes. Small and medium-sized leafy green growers commonly retrofit washing machines to dry triple-washed leaves, utilizing their spin cycle. The potential for this practice to cause microbial contamination has not been explored. This work investigated the risk of cross-contamination of Listeria associated with this practice. Listeria innocua was inoculated and dried onto spinach prior to washing, after which leaves were dried in a retrofitted washing machine. After drying, three contact surface layers of the machine were sampled. Nearly complete recovery of 98% and 99% from some contact points were observed, with the highest level of recovery observed in the bottom water-collecting contact points of the machine. Further, L. innocua from contaminated loading baskets were transferred to uninoculated spinach during the spin-drying process with a microbial recovery of 101–102 CFU/g, suggesting a risk of cross-contamination.
ISSN:2396-8370