D García1, N Gómez, P Mañas, S Condón, J Raso, R Pagán. 1. Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Zaragoza, Spain.
Abstract
AIMS: The objective was to investigate the occurrence of sublethal injury after pulsed electric field (PEF) depending on the treatment time, the electric field strength and the pH of the treatment media in two Gram-positive (Bacillus subtilis ssp. niger, Listeria monocytogenes) and six Gram-negative (Escherichia coli, Escherichia coli O157:H7, Pseudomonas aeruginosa, Salmonella serotype Senftenberg 775W, Salmonella serotype Typhimurium, Yersinia enterocolitica) bacterial strains. METHODS AND RESULTS: A characteristic behaviour was observed for the Gram-positive and Gram-negative bacteria studied. Whereas Gram-positive bacteria showed a higher PEF resistance at pH 7.0, the Gram-negative were more resistant at pH 4.0. In these conditions, in which bacteria showed their maximum resistance, a large proportion of sublethally injured cells were detected. In most cases, the longer the treatment time and the higher the electric field applied, the greater the proportion of sublethally injured cells that were detected. No sublethal injury was detected when Gram-positive bacteria were treated at pH 4.0 and Gram-negative at pH 7.0. CONCLUSIONS: Sublethal injury was detected after PEF so, bacterial inactivation by PEF is not an 'all or nothing' event. SIGNIFICANCE AND IMPACT OF THE STUDY: This work could be useful for improving food preservation by PEF.
AIMS: The objective was to investigate the occurrence of sublethal injury after pulsed electric field (PEF) depending on the treatment time, the electric field strength and the pH of the treatment media in two Gram-positive (Bacillus subtilis ssp. niger, Listeria monocytogenes) and six Gram-negative (Escherichia coli, Escherichia coli O157:H7, Pseudomonas aeruginosa, Salmonella serotype Senftenberg 775W, Salmonella serotype Typhimurium, Yersinia enterocolitica) bacterial strains. METHODS AND RESULTS: A characteristic behaviour was observed for the Gram-positive and Gram-negative bacteria studied. Whereas Gram-positive bacteria showed a higher PEF resistance at pH 7.0, the Gram-negative were more resistant at pH 4.0. In these conditions, in which bacteria showed their maximum resistance, a large proportion of sublethally injured cells were detected. In most cases, the longer the treatment time and the higher the electric field applied, the greater the proportion of sublethally injured cells that were detected. No sublethal injury was detected when Gram-positive bacteria were treated at pH 4.0 and Gram-negative at pH 7.0. CONCLUSIONS: Sublethal injury was detected after PEF so, bacterial inactivation by PEF is not an 'all or nothing' event. SIGNIFICANCE AND IMPACT OF THE STUDY: This work could be useful for improving food preservation by PEF.
Authors: Felix Schottroff; Antje Fröhling; Marija Zunabovic-Pichler; Anna Krottenthaler; Oliver Schlüter; Henry Jäger Journal: Front Microbiol Date: 2018-11-20 Impact factor: 5.640
Authors: Felix Schottroff; Justus Knappert; Pauline Eppmann; Anna Krottenthaler; Tobias Horneber; Christopher McHardy; Cornelia Rauh; Henry Jaeger Journal: Front Bioeng Biotechnol Date: 2020-04-30