The effectiveness of various disinfectants against two potentially pathogenic Yersinia enterocolitica strains (Y. enterocolitica W1024 O:9 [strain A] and Y. enterocolitica B1 O:5 Lis Xz [strain B]) on shredded lettuce was examined. Dip-wash treatments using 25,
100, and 300 ppm of chlorine at 4 and 22°C, 0.2% Orenco Peel 40, 0.1% Tergitol, 0.5% acetic acid, and 0.5% lactic acid at 22°C were performed. Surfactants and organic acids were also tested in combination with 100 ppm of chlorine. Reductions of Y. enterocolitica counts with
100 ppm (2.68 log10 for strain A and 2.36 log10 for strain B at 22°C) and 300 ppm of chlorine (3.15 log10 for strain A and 2.55 log10 for strain B at 4°C) were observed after 10 min. Inhibitory effect of different chlorine solutions was not
significantly (P < 0.05) influenced by temperature. Surfactants in combination with chlorine were more effective than surfactants alone. Treatment with 0.2% Orenco Peel 40 plus 100 ppm of chlorine resulted in reductions of 2.69 log10 CFU/g for strain A and 3.18 log10
CFU/g for strain B at 10 min. Dip solutions containing 0.1% Tergitol plus 100 ppm of chlorine produced a significant reduction of 2.73 log10 CFU/g in strain A (P < 0.05). With the 0.5% lactic acid plus 100 ppm of chlorine combination, inactivation of Y. enterocolitica
was >6 log10. The bactericidal effect of disinfectants was related to the concentration, exposure time, combination with chlorine (surfactants and organic acids), and susceptibility of each strain. Since the presence of pathogenic Y. enterocolitica on ready-to-use vegetables
represents a health hazard, treatments as effective as 0.5% lactic acid plus 100 ppm of chlorine are recommended for washing of fresh lettuce.
Document Type: Research Article
Microbiología General, Area Microbiología, Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis, Argentina
Publication date: June 1, 1999
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