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Survival and Growth of Listeria monocytogenes on Fresh-Cut Apple Slices and Its Interaction with Glomerella cingulata and Penicillium expansum

The food-borne human pathogen Listeria monocytogenes survived and its populations increased on cv. Delicious apple slices at 10 or 20°C in air or controlled atmosphere of 0.5% O₂ and 15% CO₂, but did not grow at 5°C. Controlled atmosphere had no significant effect on the survival or growth of L. monocytogenes. The pathogen populations declined over time when grown in various concentrations of apple juice and the decline was greater as the concentration of the juice decreased. Populations of L. monocytogenes inoculated into decayed apple tissue continually increased on fruit decayed by Glomerella cingulata but did not survive after 5 days on fruit decayed by Penicillium expansum. The pH of the decayed area declined from pH 4.7 to 3.7 in the case of P. expansum, but in the case of G. cingulata the pH increased from pH 4.7 to 7.0. This pH modification may be responsible for affecting the growth of the food-borne pathogen. Storage temperature, as well as the absence of postharvest pathogens such as G. cingulata, is important for maintaining the safety of fresh-cut apples.