Thermal destruction of Listeria monocytogenes in a partially-fermented dill pickle intended for refrigerator storage

Abstract

Listeria monocytogenes can be found on fresh produce and the bacteria can survive and grow in slightly acid refrigerated foods. One homemade refrigerator dill pickle procedure calls for partial fermentation of cucumbers in a salt brine at room temperature; pickles are then refrigerated up to 3 months. This study examined heat treatment procedures to ensure safety from L. monocytogenes for this procedure. Cucumbers were inoculated with a five-strain cocktail of L. monocytogenes and fermented for 7 days. Pickles were then heated at 71.1˚C, 82.2˚C, and 100˚C, and samples taken of the brine, core and skin during heating time. Total populations of L. monocytogenes were measured and log reductions in L. monocytogenes were calculated. Results revealed variability in reductions within a treatment, but the population generally decreased with increased heating time. Findings also suggest that heating at 100˚C is most practical but for additional time than what was studied.