The killing effect of pulsed electric fields (PEF) on Escherichia coli (ATCC 8739) suspended in an orange juice and milk beverage was studied. Bipolar square pulses with a pulse width of 2.5 μs were applied. Electric field strength and treatment times ranged from 15 to 40 kV/cm, and from 0 to 700 μs, respectively. A maximum of 3.83 log reductions was achieved at 15 kV/cm and 700 μs. The experimental data were fitted to Bigelow and Hülsheger models and Weibull distribution function. Results indicated that Weibull function best described the experimental data (lowest mean square error). As there were no significant differences in the values of the shape factor (n) at the electric field strength of 25-40 kV/cm, the number of parameters in the Weibull model were reduced, leading to a simplified model with a fit similar to that obtained with the full model.
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Acknowledgements The authors are grateful to the Consejo Superior de Investigaciones Científicas for providing a grant to the author and to the Generalitat Valenciana for granting the research group aid 03/147. This study was carried out with funds from CICYT project no. AGL 2003-05236-C02-01.
- Escherichia coli
- Inactivation kinetics
- Orange juice-milk
- Pulsed electric fields