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    Application of pulsed electric fields to skim milk inoculated with Staphylococcus aureus
    (Academic Press Inc Elsevier Science, 2004) Evrendilek, GA; Zhang, QH; Richter, ER
    Application of pulsed electric fields (PEF) to skim milk inoculated with Staphylococcus aureus was conducted in the study. Skim milk samples were treated by PEF, using fluid handling systems of both circulation and stepwise modes. Parameters for the PEF were 3.7 mus pulse duration time, 250 Hz pulse repetition rate, 1 ml s(-1) flow rate, 460 mus total treatment time, and 3.5 kV mm(-1) electric field strength. After the PEF-treatment, the samples were plated onto both tryptic soya agar and Baird Parker agar with egg yolk tellurite enrichment to enumerate the number of inactivated and injured cells. Survivals of PEF-treated S. aureus cells were also enumerated at refrigeration temperature for 2 weeks. There was a significant decrease in S. aureus cells caused by the two fluid handling systems (probability P < 0.05). The difference in the inactivation due to the PEF treatment with the fluid handling systems was not significant (P > 0.05). After the PEF treatment, there was no significant injury of the PEF-treated cells (P > 0.05). Relative to the control samples, there was a significant reduction in the number of the PEF-treated cells at 4degreesC for 2 weeks (P < 0.05). (C) 2003 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd.
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    Pulsed electric field treatment of liquid whole egg inoculated with Salmonella enteritidis
    (Wiley, 2004) Hermawan, N; Evrendilek, GA; Dantzer, WR; Zhang, QH; Richter, ER
    The effects of pulsed electric fields (PEF) on the inactivation of Salmonella Enteritidis inoculated into liquid whole egg (LWE) and on the physical properties and the shelf-life of LWE were studied. PEF processing conditions were 1.2 mL/s flow rate, 200 pps frequency, 2.12 mus pulse duration, 25 kV/cm electric field strength, and 250 lis total treatment time. The PEF processing caused up to 1 log(10) cfu/mL reduction in S. Enteritidis population in LWE. The PEF-treated samples were subjected to heat at 55C for 3.5 min to inactivate the remaining bacteria without denaturing the LWE. ne combination of PEF and heat treatments led to a 4.3 log(10) cfu/mL reduction in S. Enteritidis population (P < 0.05) and caused no significant change in viscosity, electrical conductivity, color, pH, and degreesBrix, relative to control samples (P > 0.05). The PEF+55C treated LWE samples presented significantly longer shelf-life at 4C compared with the control and heat treated samples (P < 0.05).