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

Abstract

In this study, the growth of Arcobacter butzleri in poultry was evaluated as a function of storage temperature (5, 22.5, and 40°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 (R2 ≥ 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 × pH) – 0.001312 (Temp × NaCl) – 0.018802 (pH × NaCl) + 0.000467 (Temp2) – 0.041711 (pH2) – 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°C) and at a pH of 9 (in the presence of 8% NaCl, at 5°C). The surface response model was statistically significant, with P < 0.0001, as evident from the Fisher F test and from coefficient determination (R2, 0.95). This model was also verified by the bias factor (Bf, 0.839), accuracy factor (Af, 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.