A model describing the kinetics of inactivation of Lactobacillus plantarum in a buffer system of different pH and in orange and apple juice

The pulsed electric fields (PEF) inactivation kinetics of Lactobacillus plantarum in McIlvaine buffer of different pH (3.5-7.0) was investigated. L. plantarum was more PEF sensitive at higher electric field strengths (E) and in media of low pH. For example a treatment at 22 kV/cm for 400 μs inactivated around 5.0, 2.8, 2.6 and 1.1 Log10 cycles the population of this microorganism at pH 3.5, 5.0, 6.5 and 7.0 respectively. A mathematical model based on the Weibull distribution accurately described concave upwards survival curves of L. plantarum. The relationship between the shape parameter (p value) of the Weibull model and the pH of the treatment medium was described by the Gompertz equation. Different multiple linear regression models were compared to describe the influence of the E and pH on the Log10 of the scale parameter (δ value) of the Weibull model. Between the models compared, a model that used two predictor variables (E, pH2) and other that used three predictor variables (E, pH, pH2) were the most suitable. The inactivation of L. plantarum in orange and apple juice was predicted satisfactory by two tertiary models developed in McIlvaine buffer.