Effectiveness of various disinfectants in the elimination of Yersinia enterocolitica on fresh lettuce

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 degrees C, 0.2% Orenco Peel 40, 0.1% Tergitol, 0.5% acetic acid, and 0.5% lactic acid at 22 degrees 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 log(10) for strain A and 2.36 log(10) for strain B at 22 degrees C) and 300 ppm of chlorine (3.15 log(10) for strain A and 2.55 log(10) for strain B at 4 degrees 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 log(10) CFU/ g for strain A and 3.18 log(10) 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 log(10) 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 log(10). 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 an 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.