Influence of the practices used in lettuce salads preparation in a catering unit in terms of food safety

Nowadays, the consumption of vegetables has assumed particular importance. Several studies over the last decade have shown that the consumption of vegetables may reduce the occurrence of cancers and lessen the risk of coronary heart disease. However, leafy green vegetables may represent some microbiological hazards. In spite of this, catering units that offer these kinds of products have to guarantee their quality and safety. The present study intended to evaluate the practices used in lettuce salads preparation in a catering unit and their influence on the quality and safety of the final product. Physic-chemical and microbiological analyses were performed on lettuce subjected to two treatments of disinfection - diluted solutions of vinegar and chlorine–tablet -, applied for 5, 10 and 15 minutes. The practice of cutting the lettuce was also evaluated. In all assays performed, none disinfectant residues were found in the lettuce washing solution obtained after the disinfection treatment. Moreover, it was found that the only type of chlorine specie found in solutions obtained with the chlorine-tablet disinfection method was free chlorine and monochloroamines, dichloroamines and trichloroamines were not detected. In microbiological terms (yeasts, mesophiles, coliforms, E. coli and moulds), the treatment with vinegar was not effective to make the product satisfactory. On the other hand, the chlorine tablet was effective in reducing microbial population to values considered acceptable, provided that the lettuce was not subjected to cutting prior to the disinfection process