Microbiological quality and vitality after striped venus clam (Chamelea gallina L.) depuration

This work was focused on the evaluation of the microbiological indices, defined by European legislation, during the depuration of clams (Chamelea gallina): the survival of depurated clams was also evaluated. The clams were subjected to a depuration conducted in 15.000-liter commercial baths with a open-circuit seawater-disinfection system that uses both filtration and ozone. Analysis for the determination of fecal coliforms, Escherichia coli, Salmonella spp, Vibrio spp, Aeromonas hydrophila, Listeria spp, clam yield, sand content and mortality were performed. The results obtained over a year period, evidenced a mean microbial reduction during depuration of 62% for E. coli and 54% for fecal coliforms. On the other hands, in a few samples both E. coli and fecal coliforms increased slightly after depuration. The viability of clam was not negatively affected by depuration: in fact, an increase of viability was observed with the exception of the samples of April. In conclusion, the depuration conditions can improve the quality of C. gallina. However its effects on microbiological quality was extremely variable, depending on environmental conditions.