INACTIVATION OF ESCHERICHIA COLI O157:H7 DURING THE STORAGE UNDER REFRIGERATION OF APPLE JUICE TREATED BY PULSED ELECTRIC FIELDS

Abstract

The sensitivity of pulsed electric fields (PEF)-treated E. coli O157:H7 cells to subsequent holding in apple juice has been evaluated. Escherichia coli O157:H7 cells in apple juice were resistant to PEF. A PEF treatment of 400 m s at any electrical field strength was not sufficient to inactivate one log 10 cycle of cells. However, PEF injured a large proportion of E. coli O157:H7 cells that became sensitive to a subsequent storage under refrigeration in apple juice. The total lethal effect of the combined process depended on the electrical field strength and storage time. The combination of a PEF treatment at 25 kV/cm for 400 m s and a subsequent storage of the apple juice under refrigeration for 48 h allowed five log 10 cycles of inactivation to be achieved. The combination of PEF and maintenance under refrigeration has been demonstrated to be an effective pasteurization method, by sufficiently reducing the presence of E. coli O157:H7 in apple juice in order to meet U.S. FDA recommendations.

Synergistic combination of heat and ultrasonic waves under pressure for Cronobacter sakazakii inactivation in apple juice

“…The study of the evolution of survival counts in refrigerated apple juice after MTS treatments was encouraged, among other reasons, because we supposed that its acidic pH would lead to the death of sublethally damaged cells caused by MTS as already observed with Escherichia coli for others technologies such as high pressure (García-Graells, Hauben, & Michiels, 1998) or pulsed electric fields (García, Hassani, Mañas, Condón, & Pagán, 2005), which would provide an additional advantage for acidic products. Results obtained indicate that C. sakazakii cells progressively died during refrigerated storage, but even upon 96 h, a certain proportion of cells still remained damaged in their cytoplasmic and outer membranes.…”

The Impact of Thermosonication and Pulsed Electric Fields on Staphylococcus aureus Inactivation and Selected Quality Parameters in Orange Juice

“…Possible recovery of the bacterial cells after treatment was investigated by spreading the samples on modified TSA (addition of 3% sodium chloride that is broadly in agreement with the method used by García et al 2005) in the same manner as stated before and extending the incubation period to 48 h. The amount of sublethally injured cells was estimated by comparing the bacterial counts after 24 h growth on non-selective TSA to the counts after 48 h on selective, modified TSA.…”

Relationship between Sublethal Injury and Inactivation of Yeast Cells by the Combination of Sorbic Acid and Pulsed Electric Fields

“…It has also been demonstrated that sublethally PEF-injured cells lose viability during subsequent storage under acidic conditions. Consequently, the combination of PEF treatment applied to apple juice and subsequent storage under refrigeration for 48 h guarantees the inactivation of at least log 10 5 cell cycles of the pathogen Escherichia coli O157:H7 (12).…”

“…Combined processes using PEF treatment must incorporate conditions that prevent the repair of cell envelopes (10,12) by the addition of food preservatives (7,9,14,18,19,23). Permeable membranes resulting from PEF treatment may facilitate the entry of antimicrobial compounds, such as organic acids, thereby increasing the antimicrobial action of the compounds (19).…”