| Pulsed Electric Field (PEF) treatment is a nonthermal food preservation method that provides inactivation of both spoilage and pathogenic organisms while minimizing the loss in physical properties during processing and storage. Microbial inactivation of microorganisms by PEF is essential to evaluate effectiveness of this emerging technology.; As a first step, fresh apple juice samples inoculated with E. coli O157:H7 and E. coli 8739 (reference organism) were treated with selected PEF parameters as a function of electric field strength and treatment time. Maximum of 5 and 5.4 log reductions in viable survivors of E. coli O157:H7 and E. coli 8739 were determined. Treatment temperature was kept under 35°C.; As a second step, skim milk samples were inoculated with S. aureus and treated by PEF using circulation and stepwise fluid handling systems. PEF parameters were 450 μs maximum total treatment time and 35kV/cm peak electric field strength. Inactivation, recovery, and survival of PEF treated S. aureus cells were studied. Inactivation of S. aureus in skim milk with both fluid handling systems resulted in a significant of 3.7 and 3 log reductions (P < 0.05). Recovery of the cells was not significantly different from control cells ( P > 0.05). Survival studies at 4°C presented that PEF treated cells were more sensitive than control cells to 2 weeks of storage ( P < 0.05).; In order to measure the effect of different stresses on PFF (20, 25 or 30 kV/cm electric field strengths) and heat (60°C for 3 min) inactivation of E. coli O157:H7, the cells were exposed to sublethal PEF treatments, acid, or temperature before PEF and heat treatments. Results showed that once the cells were exposed to pH 3.6, 4°C or 40°C temperatures for 6 h, they developed resistance to further PEF and heat treatments. ( P < 0.05). Sublethal PEF treatments, pH 5.2, pH 7.0 and 35°C temperature had no effect on the inactivation of E. coli O157:H7 cells by PEF and heat treatment (P > 0.05).; This study enhances the knowledge about PEF inactivation of significant pathogens and the effect of different stresses on the effectiveness of PEF inactivation. It helps to evaluate PEF technology as an alternative or complement to traditional methods for food preservation. |
