Comparison of Different Washing and Disinfection Protocols Used by Food Services in Southern Brazil for Lettuce ( Lactuca sativa)

Abstract

Different protocols have been used for washing and disinfecting leafy vegetables in Brazilian food services, however its effect on microbial reduction was barely studied. The aim of this study was to evaluate the effectiveness of lettuce washing and disinfecting protocols used by food services. The treatments evaluated were: washing in potable tap water (T 1); washing and dipping in potable tap water (T 2); washing with potable tap water and dipping in a solution of sodium hypochlorite (200 ppm of free chlorine) for 15 min (T 3); and 30 min (T 4); washing with potable tap water and dipping in 2% vinegar solution (T 5); and 20% vinegar solution (T 6). After the treatments, the samples were microbiologically evaluated to measure bacterial reductions. The microbial counts showed that the mean total mesophile reductions were: 0.64 log for T 1 , 0.75 log for T 2 , 2.06 log for T 3 , 2.46 log for T 4 , 1.68 log for T 5 and 1.72 log for T 6 , and the mean total coliform reductions were: 1.11 log for T 1 , 1.09 log for T 2 , 2.29 log for T 3 , 2.35 log for T 4 , 1.6 log for T 5 and 2.09 log for T 6 . Based on these results it can be concluded that protocols which used 200 ppm sodium hypochlorite for 15 to 30 min (T 3 e T 4), were the most effective, followed by treatment with 20% vinegar solution (T 6). The latter method, however, turned the lettuce dark during the distribution period.