Thermal inactivation of Salmonella, Listeria monocytogenes and Enterococcus faecium NRRL B-2354 in desiccated shredded coconut

Abstract

Desiccated shredded coconut (DSC) products have been implicated in multiple Salmonella outbreaks and Listeria monocytogenes recalls. The objective of this study was to evaluate the thermal resistance of Salmonella and L.monocytogenes in DSC as impacted by water activity (aw), and the suitability of Enterococcus faecium NRRL B-2354 as a surrogate for these foodborne pathogens during thermal processing of DSC. The inactivation kinetics of each strain in DSC fitted the log-linear model well; their thermal tolerances were inversely related to aw. The D80°C-, D85°C-, and D90°C-values of Salmonella were 38.7, 15.5, and 6.0 min at aw 0.45 compared to 53.2, 28.0, and 12.5 min at aw 0.25 under respective temperatures. For aw 0.25 and 0.45 DSC, D-values of E. faecium ranged from 49.6 to 6.5 min and 85.5 to 24.2 min at 80–90 °C, which were 1.4–1.9 and 1.1–1.3 times of those of Salmonella at the tested temperatures, indicating E. faecium is an appropriate surrogate of Salmonella during thermal processing of DSC. Compared to Salmonella, L. monocytogenes exhibited less thermal resistance in DSC. This study provides useful information for the food industry to develop thermal inactivation strategies to control Salmonella and L.monocytogenes during the post-drying process of DSC.