Culture suspensions of 45 species and strains of Listeria were prepared in tryptic soy broth with 0.6% yeast extract (TSBYE) for 24 h at 37°C, and were then diluted with phosphate buffer solution and standardized to 0.10 ± 0.01 absorbance at 600 nm. Spectrophotometer tubes containing 5 ml of TSBYE (pH 7.2) were inoculated with 0.1 ml of the standardized cultures and incubated at 4, 10 or 37°C. Absorbance readings were taken during storage. Growth curves were fitted using the Gompertz function, and growth parameters were calculated. There were major differences in lag phase duration (LPD), generation time (GT) and exponential growth rate (EGR) among species and strains of Listeria tested. Values for LPD and GT decreased (P <0.05) with increasing temperature of incubation, while EGR and maximum population density (MPD) values increased. Lag phase duration and GT values at a given temperature were lower for Listeria monocytogenes compared to other Listeria spp. At 4°C, LPDs for L. monocytogenes strains ranged from 69.8 to 270.8 h. Of the L. monocytogenes cultures tested, strain Scott A had the longest average (209.8 ± 0.1) h LPD at 4°C. At l0°C, LPDs ranged from 36.5 to 68.9 h, with Scott A being again one of the strains with the longest average LPD (62.8 ± 0.7 h). At 37°C, LPDs ranged from 4.4 to 11.1 h. Variation was also observed in GT and EGR, especially at 4°C. Although there were major variations in growth parameters due to strain and temperature, no significant (P >0.05) trends were observed in average values among different serotypes of L. monocytogenes tested.
Sliced cooked turkey bologna with various additive formulations was surface-inoculated with Lisferiu monocytogenes (2.06-2.75 log CFU/g), vacuum packaged, and stored at 4°C. Sodium acetate was most inhibitory against growth of L. monocytogenes, followed by sodium lactate and potassium sorbate, while sodium bicarbonate allowed a maximum net growth of 6.78 log CFU/g, not significantly different @>0.05) from the control (6.43 log CFU/g). Addition of 0.5% sodium acetate, 2.0% sodium lactate, or 0.26% potassium sorbate may significantly (pCO.05) decrease growth of L. monocytogenes in refrigerated turkey bologna surface-inoculated after thermal processing and slicing.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.