Effects of different sanitizing treatments on biofilms and attachment of Escherichia coli and Listeria monocytogenes on green leaf lettuce

• Published in: Food science & technology 2010-07, Vol.43 (6), p.964-970
• Main Authors: Ölmez, H., Temur, S.D.
• Format: Article
• Language: English
• Subjects: antibacterial properties; Ascorbic acid; bacterial adhesion; bacterial contamination; Biofilm; Biological and medical sciences; Escherichia coli; Food industries; Food microbiology; food pathogens; food spoilage; food surfaces; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; green leafy vegetables; Lettuce; Listeria monocytogenes; organic acids and salts; ozone; sanitizing; SEM; sodium hypochlorite
• ISSN: 0023-6438; 1096-1127
• DOI: 10.1016/j.lwt.2010.02.005

The effects of ozone (2 mg/L), chlorine (100 mg/L) and organic acid (0.25 g/100 g citric acid plus 0.50 g/100 g ascorbic acid) treatments at 10 °C for 2 min on the removal of Escherichia coli and Listeria monocytogenes cells embedded inside biofilms on the surface of lettuce leaves were studied. None of the sanitizing treatments were found effective in removing the bacterial biofilms. Initiation of biofilms was observed after 24 h of incubation. Bacterial cells appeared as individual cells, rather than clusters after 6 h incubation, thus 99.9% reductions in both E. coli and L. monocytogenes counts were achieved with all the three treatments. However, after 48 h incubation, none of the treatments resulted in higher than 90% reduction in microbial counts. Biofilm formation was demonstrated for the 48 h incubated samples with SEM images.