MODELING THE RESPONSE OFSALMONELLAMUENCHEN IN ORANGE JUICE

Abstract

ABSTRACT Salmonella Muenchen in orange juice declined (1.36, 1.18, 1.21 and 2.5 log cfu/mL) after 5–11 days at 6, 10, 15 and 20C, respectively. Modified Weibull, Power and Gompertz models were developed. The primary Gompertz, Power and Weibull models had a root mean square error (RMSE) between 0.04 and 0.14. The primary Gompertz model predicted (6C) a lag time period and an exponential decline rate of 4.1 days and 0.211 log cfu/mL/day, respectively. As the temperature increased (from 6 to 20C), the death rate constant, b, of the primary Power model increased (from 0.0498 to 0.579 cfu/mL/day), while the first decimal population reduction, δ, of the primary Weibull model decreased (from 9.3 to 2.6 days). The secondary Weibull model had the lowest RMSE of 0.0836. The secondary Power, Weibull and Gompertz models under predicted the S. Muenchen population and were characterized by bias factor values of the 0.96, 0.72 and 0.51, respectively. PRACTICAL APPLICATIONS This study modeled the response of Salmonella Muenchen in orange juice (OJ). Using three mathematical models (primary and secondary modified Weibull, Power and Gompertz), it evaluated the decline of this pathogen over time (up to 11 days), at temperatures in the range of 6–20C. This study may assist the industry applying similar models for the evaluation of the survival of pathogens such as Salmonella during processing, treatments and storage conditions. The applications of models may save time and materials in some quality controls operations and in establishing and evaluating Hazard Analysis and Critical Control Points programs. It became clear that although S. Muenchen declined, it was not totally eliminated during a storage period of up to 11 days. Thus, if OJ and similar juices become contaminated with a pathogen such as S. Muenchen, a safety hazard may exist.