Pulsed electric field processing of different fruit juices: Impact of pH and temperature on inactivation of spoilage and pathogenic micro-organisms

Pulsed electrical field (PEF) technology can be used for the inactivation of micro-organisms and therefore for preservation of food products. It is a mild technology compared to thermal pasteurization because a lower temperature is used during processing, leading to a better retention of the quality. In this study, pathogenic and spoilage micro-organisms relevant in refrigerated fruit juices were studied to determine the impact of process parameters and juice composition on the effectiveness of the PEF process to inactivate the micro-organisms. Experiments were performed using a continuous-flow PEF system at an electrical field strength of 20 kV/cm with variable frequencies to evaluate the inactivation of Salmonella Panama, Escherichia coli, Listeria monocytogenes and Saccharomyces cerevisiae in apple, orange and watermelon juices. c data showed that under the same conditions, S. cerevisiae was the most sensitive micro-organism, followed by S. Panama and E. coli, which displayed comparable inactivation kinetics. L. monocytogenes was the most resistant micro-organism towards the treatment conditions tested. A synergistic effect between temperature and electric pulses was observed at inlet temperatures above 35 °C, hence less energy for inactivation was required at higher temperatures. Different juice matrices resulted in a different degree of inactivation, predominantly determined by pH. The survival curves were nonlinear and could satisfactorily be modeled with the Weibull model.