Survival of Listeria monocytogenes on organic Honeycrisp and Fuji apples during storage at 5, 12 and 22.5°C

Abstract

This study aimed to evaluate the survival of Listeria monocytogenes on organic Honey Crisp ( HC ) and Fuji ( FJ ) apples during storage at various temperatures. Fresh organic HC and FJ apples (without waxing coating) obtained from local wholesale market were inoculated with a 2-strain mixer of L. monocytogenes followed by storing at 5.0 [22.9% Relative Humidity (RH)], 12.0 (37.0% RH), and 22.5 °C (50.4% RH) for 60, 35, 7 days, respectively, and periodically (day-0 to 60) analyzing microbial populations. Surviving L. monocytogenes were spread-plated on Modified-Oxford agar after 10 or 100-fold serial dilution. Data was analyzed using the mixed-model-procedure of SAS and GinaFit software. The initial populations of L. monocytogenes on HC and FJ apples were 6.23–6.89 log 10 CFU/apple for storage at 5, 12, and 22.5 °C. The pathogen survival cell counts decreased ( P < 0.05) to 2.34 to 4.05, 2.72 to 2.98, and 2.47 to 3.75 log 10 CFU/apple by the end of the storage at 5, 12, and 22.5 °C. L. monocytogenes was more vulnerable ( P < 0.05) on FJ than HC apples and at room temperature than cold storage temperatures. The inactivation parameters calculated from the Linear, Weibull, and Biphasic models generally are consistent with the pathogen survival curves with few exceptions. Results of this study filled the data gap for understanding of microbiological risks associated with postharvest practices of tree fruit production. Future studies are needed to quantify the natural wax amount on various organic apples and develop pre- and postharvest intenvention strategies for inactivation of foodborne pathogens on apples as well as other tree fruits. • L. monocytogenes decreased on apples during storage. • L. monocytogenes was more vulnerable on Fuji than Honey Cripsy apples. • Inactivation parameters fit the Linear, Weibull, and Biphasic models.