Multiple recalls and outbreaks involving Listeria monocytogenes-contaminated apples have been linked to the post-harvest packing environment where this pathogen persists. The research presented here addresses the effect of both apple fruit attributes and post-harvest conditions on L. monocytogenes survival. First, L. monocytogenes survival was assessed on apples as affected by harvest year, apple cultivar, storage atmosphere, and growth conditions. The second portion of the study investigated the chemical composition and morphology differences of cuticular wax in Gala and Honeycrisp apples. The influence of natural cuticular wax composition and structure is important to investigate as it impacts apple fruit quality and food safety. Finally, before apple fruit are shipped to market, they are treated with commercial coatings to enhance quality. We assessed L. monocytogenes survival to determine the impact shellac and carnauba surface coatings have during storage in solution or applied to a contaminated surface. On the surface of apples, L. monocytogenes populations gradually decreased but were still quantifiable in most samples after 7 months. Apple cultivar significantly impacted L. monocytogenes survival (p < 0.05) during both harvest years with greater reductions (p < 0.05) seen on Gala compared to Granny Smith and Honeycrisp. Gala apples had more alkanes (g/cm2 of peel) overall for alkane compounds compared to Honeycrisp. In Gala apples the main component of the cuticular wax was nonacosane. Nonacosane content (g/cm2 of peel) in the cuticular waxes was greater (p < 0.01) on Gala (108.77±0.36) than on Honeycrisp (46.12±4.86). After just 12 hours of storage, in the shellac surface coating solution, L. monocytogenes was no longer detectable, compared to the carnauba surface coating solution which still supported survival (2.4-4.0 log CFU/mL) after 14 days. These findings should aid in the development of improved L. monocytogenes intervention strategies and inform manufacturers looking for natural food safety solutions.
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