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Applied and Environmental Microbiology, June 2007, p. 3814-3821, Vol. 73, No. 12
0099-2240/07/$08.00+0     doi:10.1128/AEM.00517-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

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

M. Somolinos, D. García, S. Condón, P. Mañas, and R. Pagán*

Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, C/ Miguel Servet, 177, 50013 Zaragoza, Spain

Received 7 March 2007/ Accepted 17 April 2007

The objective of this study was to investigate the occurrence of sublethal injury after the pulsed-electric-field (PEF) treatment of two yeasts, Dekkera bruxellensis and Saccharomyces cerevisiae, as well as the relation of sublethal injury to the inactivating effect of the combination of PEF and sorbic acid. PEF caused sublethal injury in both yeasts: more than 90% of surviving D. bruxellensis cells and 99% of surviving S. cerevisiae cells were sublethally injured after 50 pulses at 12 kV/cm in buffer at pHs of both 7.0 and 4.0. The proportion of sublethally injured cells reached a maximum after 50 pulses at 12.0 kV/cm (S. cerevisiae) or 16.5 kV/cm (D. bruxellensis), and it kept constant or progressively decreased at greater electric field strengths and with longer PEF treatments. Sublethally PEF-injured cells showed sensitivity to the presence of sorbic acid at a concentration of 2,000 ppm. A synergistic inactivating effect of the combination of PEF and sorbic acid was observed. Survivors of the PEF treatment were progressively inactivated in the presence of 2,000 ppm of sorbic acid at pH 3.8, with the combined treatments achieving more than log10 5 cycles of dead cells under the conditions investigated. This study has demonstrated the occurrence of sublethal injury after exposure to PEF, so yeast inactivation by PEF is not an all-or-nothing event. The combination of PEF and sorbic acid has proven to be an effective method to achieve a higher level of yeast inactivation. This work contributes to the knowledge of the mechanism of microbial inactivation by PEF, and it may be useful for improving food preservation by PEF technology.

* Corresponding author. Mailing address: Dpto. PACA, Facultad de Veterinaria, Universidad de Zaragoza, C/ Miguel Servet, 177, 50013 Zaragoza, Spain. Phone: 34-976-762675. Fax: 34-976-761590. E-mail: pagan{at}unizar.es

{triangledown} Published ahead of print on 27 April 2007.

Applied and Environmental Microbiology, June 2007, p. 3814-3821, Vol. 73, No. 12
0099-2240/07/$08.00+0     doi:10.1128/AEM.00517-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Somolinos, M., Garcia, D., Pagan, R., Mackey, B. (2008). Relationship between Sublethal Injury and Microbial Inactivation by the Combination of High Hydrostatic Pressure and Citral or tert-Butyl Hydroquinone. Appl. Environ. Microbiol. 74: 7570-7577 [Abstract] [Full Text]  


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