Mathematical Models to Describe Kinetic Behavior of Campylobacter jejuni in Dried Meat Products

Introduction: Campylobacter jejuni has been cause of foodborne outbreaks. Even though C. jejuni has susceptibility to various factors such as temperature, water activity and pH, the pathogen is found in raw meat as well as processed meat products. In addition, many studies indicated that low temperatures and vacuum packaging may increase C. jejuni outbreak.

Purpose: The objective of this study was to develop mathematical models to predict the kinetic behavior of C. jejuniin dried meat products.

Methods: Purchased seasoned and non-seasoned dried meat products were cut into 10-g portions. A mixture (0.1 mL) of C. jejuni strains ATCC33560 and NCTC11168 was inoculated into samples to obtain 5-6 Log CFU/g, and the samples were stored aerobically at 10^oC, 20^oC, 25^oC, and 30^oC. C. jejuni cell counts were enumerated on modified CCDA-Preston, and these results were used to develop a primary model (Weibull model) to calculate Delta (time required for first decimal reduction) and p (shape of curves). Delta values were further analyzed with a secondary model (Cubic model and Modified simple exponent model) as a function of storage temperature. To evaluate the accuracy of the model prediction, root mean square error (RMSE) was calculated by comparing the predicted data with observed data.

Results: In both seasoned and non-seasoned dried meat products, C. jejuni surviving cell counts gradually decreased at all temperatures. The Delta values from the primary model were longer (P<0.05) in 10-25^oC than 30^oC. No differences in p values were observed among temperatures. The secondary model well-described the temperature effect on Delta with 0.972-0.983 of R². RMSE values with 0.643 (seasoned jerky) and 0.519 (non-seasoned jerky) suggested that the model performance was acceptable.

Significance: This result suggests that the developed models should be useful in describing the kinetic behavior of C. jejuniin dried meat products.