Defining treatment conditions for pulsed electric field pasteurization of apple juice

The influence of temperature and the presence of N-alpha-lauroyl ethylester (ethyl lauroyl arginate. LAE) on the inactivation caused by continuous pulsed electric field treatments (PEF) in Escherichia coli O157:H7 suspended in apple juice have been investigated to define treatment conditions applicable at industrial scale that promote an equivalent safety level when compared with thermal processing. In the range of experimental conditions investigated (outlet temperature: 20-40 degrees C, electric field strength: 20-30 kV, treatment time: 5-125 mu s) at outlet temperatures equal or lower than 55 +/- 1 degrees C, the inactivation of E. coli O157:H7 treated in apple juice ranged from 0.4 to 3.6 Log(10) cycles reduction and treated in apple juice supplemented with LAE (50 ppm) ranged from 0.9 to 6.7 Log(10) cycles reduction. An empirical mathematical model was developed to estimate the treatment time and total specific energy input to obtain 5 Log(10) cycles reduction in the population of E. coli O157:H7 suspended in apple juice supplemented with 50 ppm of LAE at different electric field strengths and inlet temperatures. Treatment conditions established for E. coli O157:H7 were validated with other PEF resistant Gram-positive (Listeria monocytogenes, and Staphylococcus aureus) and Gram-negative (Salmonella enterica serovar Typhimurium) strains. When the treatment was applied to the apple juice, a treatment of 25 kV/cm for 63 mu s corresponding with an outlet temperature of 65 degrees C and input energy of 125 kJ/kg was required to achieve more than 5 Log(10) cycles in the four strains investigated. The addition of LAE reduced the treatment time required to obtain an equivalent inactivation (>5 Log(10)) cycles) in the four microorganisms to 38.4 Its, the outlet temperature to 55 degrees C, and the input energy to 83.2 kJ/kg. (C) 2011 Elsevier B.V. All rights reserved.