Purpose: This study isolated and serotyped L. monocytogenes from smoked salmon, and developed a dynamic model to predict L. monocytogenes survival in smoked salmon.
Methods: Thirty two of smoked salmon samples from retail markets were plated on PALCAM agar. Isolated L. monocytogenes colonies were identified by 16s rRNA analysis, and presences of hlyA and prs genes were investigated by PCR. Serotypes were also determined by multiplex PCR. To develop a dynamic model, L. monocytogenes cell counts were obtained from smoked salmon during aerobic storage at 4-20oC for 8 days. The Baranyi model (primary model) was fitted to the microbiological data to calculate maximum specific growth rate (µmax; log CFU/g/h) and lag phase duration (LPD; h). Polynomial equations (secondary model) were then fitted to the kinetic parameters. A dynamic model was developed with primary and secondary models. Root mean square error (RMSE) was calculated to evaluate the model performance.
Results: Of 32 smoked salmon samples, one sample (3.1%) was contaminated with L. monocytogenes, and the serotype was determined to be 1/2a. At 4-20°C, L. monocytogenes cell counts in smoked salmon increased at 0.01-0.13 log CFU/g/h of µmax. LPDs were decreased from 74.2 to 4.8 h as temperature increased. Developed secondary model was appropriate to describe the effect of storage temperature on the kinetic parameters with 0.973-0.990 of R2. The performance of developed dynamic model was appropriate at changing temperature with 0.368 of RMSE.
Significance: The results indicate that L. monocytogenes is contaminated in smoked salmon in S. Korea, and the developed dynamic model should be useful in describing kinetic behavior of L. monocytogenes.