Kinetic Behavior of Listeria monocytogenes in Diced Radish Kimchi

Introduction: Although kimchi is known to become safe microbiologically through fermentation, foodborne outbreaks and recalls, especially for Listeria monocytogenes, have been occurred.

Purpose: The objective of this study was to develop a predictive model to describe the kinetic behavior of L. monocytogenes in diced radish kimchi.

Methods: A 9-strain mixture of L. monocytogenes (NCCP10805, NCCP10806, NCCP10807, NCCP10808, NCCP10809, NCCP10810, NCCP10811, NCCP10920, and NCCP10943) was inoculated in diced radish kimchi, and the target level was 4 log CFU/g. The samples were then stored at 4°C (14 days), 15°C (10 days), and 25°C (10 days), and L. monocytogenes (PALCAM) and lactic acid bacteria (de Man, Rogosa and Sharpe agar) were enumerated. L. monocytogenes cell count data were fitted to a primary model (Baranyi model) to calculate death rate (log CFU/g/h).

Results: In the primary model, the death rates of L. monocytogenes sin diced radish kimchi were decreased slightly as storage temperature increased, thus, the secondary model was not developed. However, the bacteria maintained survival at initial level during fermentation at all temperatures, indicating that the pathogen might not be affected by lactic acid bacteria.

Significance: This result indicates that L. monocytogenes may be a risk if they present initially in diced radish kimchi during fermentation.