Understanding a foodâs ability to support the growth and/or survival of a pathogen throughout the supply chain is essential to minimizing large-scale contamination events. The purpose of this study was to examine the behavior (growth and/or survival) of Listeria monocytogeneson broccoli and cauliflower florets stored under different post-harvest temperatures utilized along the supply chain. Broccoli and cauliflower samples were inoculated at approximately 3 log CFU/g and stored at temperatures: 23Â±2, 12Â±2, 4Â±2, and -18Â±2Â°C. Samples were enumerated at 0, 0.167 (4 h), 1, 2, 3, and 4 (23Â±2Â°C); 0, 0.167, 1, 2, 3, 4, 7, 10 and 14 (12Â±2Â°C); 0, 0.167, 1, 2, 3, 4, 7, 10, 14, 21 and 28 (4Â±2Â°C); and 0, 1, 7, 28, 56, 84, 112, 140 and 168 (-18Â±2Â°C) d. L. monocytogenes populations were determined from plating samples onto tryptic soy agar and modified Oxford agars supplemented with nalidixic acid. Broccoli and cauliflower supported the growth of L. monocytogenes at 23, 12, and 4Â°C, with higher growth rates observed at higher temperatures. Populations of L. monocytogenes on broccoli and cauliflower samples significantly increased within 1 d at 23Â°C (1.6 and 2.0 log CFU/g, respectively) (P â¤ 0.05). At 12Â°C, populations of L. monocytogenes on broccoli and cauliflower samples significantly increased over 14 d by 1.4 and 1.9 log CFU/g, respectively (P â¤ 0.05). No significant difference over time was observed in L. monocytogenes populations on broccoli and cauliflower samples held at refrigeration, until populations began to grow by d 10 for both commodities (P> 0.05). Under frozen storage (-18Â°C),populations of L. monocytogenes survived on broccoli and cauliflower at least up to 168 d. Broccoli and cauliflower may be stored at lower temperatures to minimize L. monocytogenes growth potential, as growth rates were lower at 4Â°C, compared to at 12 and 23Â°C.
ABSTRACT Listeria monocytogenes may be present in produce-associated environments (e.g., fields, packing houses); thus, understanding its growth and survival on intact, whole produce is of critical importance. The goal of this study was to identify and characterize published data on the growth and/or survival of L. monocytogenes on intact fruit and vegetable surfaces. Relevant studies were identified by searching seven electronic databases: AGRICOLA, CAB Abstracts, Center for Produce Safety funded research project final reports, FST Abstracts, Google Scholar, PubMed, and Web of Science. Searches were conducted using the following terms: Listeria monocytogenes, produce, growth, and survival. Search terms were also modified and “exploded” to find all related subheadings. Included studies had to be prospective, describe methodology (e.g., inoculation method), outline experimental parameters, and provide quantitative growth and/or survival data. Studies were not included if methods were unclear or inappropriate, or if produce was cut, processed, or otherwise treated. Of 3,459 identified citations, 88 were reviewed in full and 29 studies met the inclusion criteria. Included studies represented 21 commodities, with the majority of studies focusing on melons, leafy greens, berries, or sprouts. Synthesis of the reviewed studies suggests L. monocytogenes growth and survival on intact produce surfaces differ substantially by commodity. Parameters such as temperature and produce surface characteristics had a considerable effect on L. monocytogenes growth and survival dynamics. This review provides an inventory of the current data on L. monocytogenes growth and/or survival on intact produce surfaces. Identification of which intact produce commodities support L. monocytogenes growth and/or survival at various conditions observed along the supply chain will assist the industry in managing L. monocytogenes contamination risk. HIGHLIGHTS L. monocytogenes growth and/or survival on intact produce differed by commodity. Intact produce held at ≥20°C had the highest L. monocytogenes growth rates. Produce surface and storage conditions affected L. monocytogenes growth and/or survival. Microbial carrying capacity is crucial to characterizing growth and/or survival patterns. Studies need to describe experimental conditions (e.g., relative humidity) for modeling efforts.