Persistence of Listeria monocytogenes on dried apple products: influence of storage temperature, water activity, cultivar, and product style.

Although low-moisture foods do not support growth, Listeria monocytogenes can remain viable for extended periods, and long-term survival data for dried fruit systems remain limited. In this study, we evaluated the survival of a three-strain cocktail of L. monocytogenes on dried apple products under different water activities (aw), storage temperatures, apple cultivars, and product styles during 48 weeks of storage. L. monocytogenes (∼9.0 log10 CFU/g) was inoculated onto homemade and commercially prepared apple products and equilibrated to aw 0.25 or 0.45 before storage at 22 °C or 4 °C. Across the evaluated conditions, L. monocytogenes populations consistently declined more at 22 °C than at 4 °C. At 22 °C, populations on homemade Granny Smith and Gala slices decreased by ∼7.8- and 5.3-log, respectively, over 48 weeks, compared with reductions of ∼1.9 and 0.9-log, respectively, at 4 °C. Greater population reductions occurred at aw 0.45 than at aw 0.25, particularly at 22 °C (e.g., ∼7.0- vs 4.7-log, respectively, on commercial slices). L. monocytogenes exhibited greater persistence on Gala than on Granny Smith slices. Survival patterns also differed between homemade and commercially prepared products and among product styles. At 22 °C and aw 0.45, reductions on small (1 × 1 cm) commercial slices reached ∼7.0-log, compared with ∼5.0-log on larger (3 × 3 cm) slices. Differences among product styles were less pronounced at 4 °C, where reductions ranged from ∼1.5 to 2.0-log across conditions. Overall, L. monocytogenes demonstrated long-term persistence in dried apple products, with the magnitude of population decline varying with storage temperature, aw, cultivar, preparation method, and product style. These findings provide commodity-specific data relevant to evaluating L. monocytogenes survival in dried fruit products.