Scanning Electron Microscopy of Thermo-Sonicated Listeria Innocua Cells
Listeria innocua cell structure was studied after conducting thermo-sonication treatments (24 kHz, 400 W, 120μm, 63°C) in order to establish a possible mechanism of cell inactivation. Raw and whole cow’s milk was used as the medium of treatment, and samples were analyzed after 10 min of thermo-sonication. Scanning electron microscopy (SEM) was used to identify possible injuries in cells after the treatment. The control sample showed complete integrity and non-disruption of the cell membrane, the characteristic rod shape of Listeria cells could be seen, and a smooth surface was clearly observable. After 10 min of sonication, the lethal effects of caviation were observed as the presence of small holes in the cell surface, perforations outside the cell wall, surface granules and disruption of the cell membrane. These preliminary effects are responsible for cell inactivation during the first minutes of treatment, and they increase the lethality of the sonication with longer treatment times.
KeywordsListeria Monocytogenes Ultrasonic Irradiation Early Stationary Phase Microbial Inactivation Longe Treatment Time
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- Bermúdez-Aguirre, D., Mobbs, T., Versteeg, K., and Barbosa-Cánovas G.V., 2005, Inactivation of Listeria innocua by Ultrasound of Low Frequency in Raw Whole Milk, in: 2005 IFT Annual Meeting Book of Abstracts. Institute of Food Technologists, New Orleans, 16–20.Google Scholar
- Cabeza, M.C., Ordóñez, J.A., Cambero, I., De la Hoz, L., and García M.L., 2004, Effect of Thermoultrasonication on Salmonella Enterica Serovar Enteridits in Distilled Water And Intact Shell Eggs . J. Food Protect. 67(9):1886–1891.Google Scholar
- Jay J., 1992, Modern Food Microbiology. 4th ed., Van Nostrand Reinhold, New York.Google Scholar
- Martin, S.E., and Fisher C.W., 2000, Listeria monocytogenes, in: Encyclopedia of Food Microbiology, R.K. Robinson, C.A. Batt and P.D. Patel (eds.), Academic Press, Great Britain, Vol. 2, pp. 1228.Google Scholar
- Raso, J., Pagán, R., Condón, S., and Sala F.J., 1998, Influence of Temperature and Pressure on the Lethality of Ultrasound. Appl. Environ. Microb. 64 (2):465–471.Google Scholar