Development of an absorbance-based response model for monitoring the growth rates of Arcobacter butzleri as a function of temperature, pH, and NaCl concentration

In this study, the growth of Arcobacter butzleri in poultry was evaluated as a function of storage temperature (5, 22.5, and 40 degrees C), pH (5, 7, and 9), and NaCl concentration (0, 4, and 8%). A predictive model was developed using the absorbance-based response surface methodology to describe the growth rate. The primary model was obtained to predict a growth rate with a good fit (R-2 >= 0.95), and the secondary model was obtained by nonlinear regression analysis and calculated as follows: Growth rate = -2.267274 - 0.024181 (Temp) + 0.6459384 (pH) + 0.1926227 (NaCl) + 0.0024661 (Temp x pH) - 0.001312 (Temp x NaCl) - 0.018802 (pH x NaCl) + 0.000467 (Temp(2)) - 0.041711 (pH(2)) - 0.007426 (NaCl2). Our data showed that the growth of A. butzleri can be completely inhibited at a pH of 5 (in the absence of NaCl, at 5 degrees C) and at a pH of 9 (in the presence of 8% NaCl, at 5 degrees C). The surface response model was statistically significant, with P < 0.0001, as evident from the Fisher F test and from coefficient determination (R-2, 0.95). This model was also verified by the bias factor (B-f, 0.839), accuracy factor (A(f), 1.343), and mean square error (MSE, 0.0138). The newly developed secondary models of growth rate for A. butzleri could possibly be incorporated into a tertiary modeling program such as Pathogen Modeling Program (U.S. Department of Agriculture [USDA]) and Food Micro Model (in the United Kingdom). As a result, they could be used to predict the growth kinetics of A. butzleri as a function of a combination of environmental factors. Ultimately, the developed model can be used to reduce A. butzleri in poultry production, processing, and distribution, thereby enhancing food safety.