Development of Predictive Model for Campylobacter jejuni Survival on Beef Tartare

Introduction: Recently, foodborne illness caused by Campylobacter spp. has been increased in S. Korea, especially by raw meat. Beef tartare is a food eaten raw, and this is consumed commonly in certain countries. For this reason, the probability of Campylobacter foodborne illness could be high.

Purpose: This study developed the models to predict the survival of Campylobacter jejuni in beef tartare.

Methods: A mixture of C. jejuni strains ATCC33560 and NCTC11168 was prepared, and 0.1 ml of the mixture were inoculated into beef tartar samples (25 g) to obtain 6-7 log CFU/g, followed by aerobic-storage at 4°C, 10°C, 15°C, 25°C, and 30°C for up to 984 h, depending on temperature. During storage, samples were analyzed microbiologically to enumerate C. jejuni populations with modified CCDA-Preston. The survival data were analyzed with the Weibull model to calculate δ which is required time (h) for first decimal reduction and p which describes the shape of curves. The parameters were then further analyzed with the Davey model to describe the effect of temperature on the parameters. Subsequently, root mean square error (RMSE) was calculated to evaluate the differences between observed and predicted data from models.

Results: C. jejuni cell counts were gradually decreased at low temperatures (4°C and 10°C), but the cell counts were dramatically decreased (P<0.05) at 15°C, 25°C, and 30°C. δ values decreased from 657.1 h to 9.7 h as storage temperature increased, and temperature effect on curve shape was observed. In addition, the secondary model with the Davey model was appropriate with 0.927 and 0.731 of R² in δ and p, respectively^. From validation, RMSE with 0.475 suggested that prediction by the developed model was appropriate.

Significance: These results indicate that C. jejuni can survive longer at lower temperature, and the developed models should be useful in predicting C. jejuni survival in beef tartare.