Recent apple-related recall and outbreak events have exposed a need for better food safety controls along the supply chain. Following harvest apples can be stored under a controlled atmosphere for up to one year after harvest before packing and distribution, making the crop susceptible to many opportunities for contamination that increase the quantity of postharvest losses. Botrytis cinerea (BC) and Penicillium expansum (PE) cause significant rot-associated losses to the apple industry. These fungi can colonize and destroy apple tissue as storage duration increases, which may also impact the growth of saprophytic foodborne pathogens like Listeria monocytogenes . Thus the objective of this study was to observe population changes of Listeria innocua (LI) as a surrogate for L. monocytogenes on apples inoculated with BC or PE under long-term controlled atmosphere cold storage conditions to identify the effect of postharvest mold growth on growth patterns of a food safety-relevant microorganism. ‘Gala’ and ‘WA 38’ apples (n = 1,080) were harvested, treated with pyrimethanil, and inoculated with LI only, or LI and one of the mold species on wounded and unwounded portions of the apple equator. Apples were treated with 1-methylcyclopropene and stored at a controlled atmosphere (2kPa O 2 , 1kPa CO 2 , 1°C) for 1 week and 1, 3, 6, 9 and 11 months before enumeration. After three months LI consistently fell below the limit of detection (2.35 log CFU/g) and samples were enriched following a modified BAM method with PCR confirmation. Listeria persistence was dependent on the storage duration and type of fungal contamination ( p < 0.05). Surface wounding may impact these trends, depending on the apple variety. Prevalence of LI was greater in ‘Gala’ apples. Future studies should more closely examine the interactions on the fruit surface that occur during the seemingly critical timeframe of three-to-six months in storage.
Persistence of Listeria innocua on Fresh Apples During Long-Term Controlled Atmosphere Cold Storage with Postharvest Fungal Decay
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Alexis Hamilton, Blanca Ruiz-Llacsahuanga, Manoella Mendoza, James Mattheis, Ines Hanrahan, Faith J. Critzer; Persistence of Listeria innocua on Fresh Apples During Long-Term Controlled Atmosphere Cold Storage with Postharvest Fungal Decay. J Food Prot 2021; doi: https://doi.org/10.4315/JFP-21-232
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