Mathematical Model to Describe Campylobacter Survival in Processed Ground Meat Products

Introduction: In recent, Campylobacter foodborne outbreaks have been increased and the outbreaks are usually caused by cross-contamination between raw meat and cooked meat products, which have a short shelf-life at cold temperature.

Purpose: The objective of this study was to develop the mathematical model to describe Campylobacter survival in processed ground meat products.

Methods: One tenth-milliliter aliquots of C. jejuni strains ATCC33560 and NCTC11168 were inoculated into 25-g of frozen pork cutlets (model food for processed ground meat products) to obtain 6-7 Log CFU/g. The samples were stored at 4°C, 10°C, 15°C, 25°C, and 30°C in aerobic condition, and C. jejuni surviving cell counts were determined by plating the samples on modified CCDA-Preston at appropriate time interval. The survival data were fitted by the Weibull model to determine δ (the time of first decimal reduction, h) and p (shape of curve). δ and p data were further analyzed by the Davey model as a function of storage temperature. The performance of the developed model was evaluated with the root mean square error (RMSE) by comparing predicted values to observed values.

Results:  C. jejuni cell counts were decreased at all temperatures (4°C, 10°C, 15°C, 25°C, and 30°C). Low temperatures (4-15^oC) showed longer (P < 0.05) δ values (37.2-94.2 h) than those (3.0-3.9 h) of high temperatures (25-30°C). p values were ranged from 0.5 to 1.2, and temperature effect on p values was observed. In addition, the secondary model (Davey model) of δ and p was appropriate with 0.890 and 0.910 of R². Validation result showed that the performance of developed model was appropriate with 0.589 of RMSE.

Significance: These results indicate that C. jejuni can survive in processed ground meat products for long time at lower temperature, and the developed model is appropriate to describe the kinetic behavior of Campylobacter in processed ground meat products.