Effect of Different Pre-Growth Temperatures on the Survival Kinetics of Salmonella enterica and Listeria monocytogenes in Fresh-Cut Salad during Refrigerated Storage

Abstract

The effect of the pre-growth temperature of bacterial cultures on their subsequent survival kinetics in fresh-cut produce during refrigerated storage was investigated in this study. Three-strain cocktails of Listeria monocytogenes and Salmonella enterica, cultured at different growth temperatures (4, 21, and 37 °C) were inoculated on fresh-cut mixed salad and on individual produce in the mixed salad. The inoculated samples were stored at 4 °C and 80 ± 2% relative humidity (RH) for up to 72 h and the growth, survival, or death kinetics were determined at regular intervals. The results indicate that depending upon the type of pathogen tested, the pre-growth temperature(s) and the type of produce showed a significant (p ≤ 0.05) effect on the survival kinetics. Among the tested produce, mixed salad showed the highest reduction in L. monocytogenes pre-grown at 37 °C (1.33 log CFU/g) followed by red cabbage (0.56 log CFU/g), iceberg lettuce (0.52 log CFU/g), and carrot (−0.62 log CFU/g), after 72 h, respectively. In the case of Salmonella, carrot showed the highest reduction (1.07 log CFU/g for 37 °C pre-grown culture) followed by mixed salad (0.78 log CFU/g for 37 °C pre-grown culture), cabbage (0.76 log CFU/g for 21 °C pre-grown culture), and lettuce (0.65 log CFU/g for 4 °C pre-grown culture), respectively. Among the tested ComBase predictive models, the Baranyi–Roberts model better fitted the experimental data. These findings indicate that the appropriate selection of pre-growth environmental conditions is critical to better understand the kinetics of foodborne pathogens.

Modelling the Growth of Listeria monocytogenes on Fresh-Cut Cucumbers at Various Storage Temperatures

“…In this study, L. monocytogenes growth on fresh green coconut was successfully modelled using the Baranyi model [22], and, then, a secondary model based on the Ratkowsky model was derived to predict growth parameters (maximum growth rate, lag time, and maximum population) as a function of temperature (5-35 • C) [23]. The growth of Listeria monocytogenes on fresh-cut mixed salad at different pre-growth temperatures (4, 21, and 37 • C) was fit using the Baranyi-Roberts mode [24]. The growth kinetics of Salmonella on three types of mangoes ('Ataulfo', 'Kent', and 'Tommy Atkins') was also evaluated with Linear and Baranyi models at 12, 20, and 30 • C [25].…”