Comparing the pulsed electric field resistance of the microorganisms in grape juice: Application of the Weibull model

- Effects of PEF treatment on three microorganisms in grape juice were studied.
- Both pathogenic and spoilage microorganisms in grape juice were investigated.
- The treatment time and specific energy were used as control parameters.

Pulsed electric field (PEF) technology is a nonthermal food preservation technology that is based on the use of electric field to eradicate microorganisms in foods. In present study, the PEF resistance of three strains of microorganisms (Staphyloccocus aureus, Escherichia coli DH5α and Saccharomyces cerevisiae) in grape juice was investigated by applying PEF treatments ranging from 9 kV/cm to 27 kV/cm and from 34 μs to 275 μs at an initial treatment temperature of 40 °C. The temperature measurement at particular locations in the processing line showed a general trend for all the composites: greater temperature increasing as the electric field strength and treatment time values increased. In all experimental conditions used in this investigation temperature increments were always lower than 8.8 °C. The obtained survival curves indicated that the inactivation of three strains increased with electric field strength and treatment time, or specific energy. The S. cerevisiae exhibited the least resistance to PEF treatments, S. aureus the second, E. coli DH5α the third. The experimental kinetics of inactivation by PEF of these microorganisms has been described by mathematical equations based on the modified Weibull model, using treatment time and specific energy as the control parameters. Both R2 and RMSE indicated a slightly higher degree of correlation between experimental and fitted values was achieved for models in terms of specific energy. Finally, the predicted inactivation curves from the established model were validated to evaluate the performance of the model using a total of 36 datasets for three microorganisms. Models built in terms of specific energy showed better accuracy than those in terms of treatment time. Whether treatment time or specific energy was used as control parameter of the model, all the bias factors ranged within the proposed acceptable limits. Overall, 80.6% and 85% of the mean prediction errors for above two models were in the acceptable prediction zone, more than 70% of which was considered as a threshold for a simulation model to provide acceptable predictions. The validation results indicated that the Weibull models were safe for predicting inactivation curves of S. aureus, E. coli DH5α and S. cerevisiae by PEF in grape juice. Therefore, the developed tertiary models were useful for assessing the lethal effects of different parameters on PEF treatment results and evaluating the relation between cost and benefit of a potential implementation of PEF technology in industrial production processes.