Depuration of striped venus clam (Chamelea gallina L.): effects on microorganisms, sand content, and mortality

This study was focused on the evaluation of the microbiological indices, defined by European legislation, before and after the depuration of clams (Chamelea gallina) landed in category B seawater. The survival of depurated clams and the meat yield were also evaluated. The results obtained from October 2002 to September 2003 evidenced a mean microbial reduction during depuration of 62% for Escherichia coli and 54% for fecal coliforms (FC). All the samples had FC counts below the limit after 24 h depuration with the exception of the August samples. E. coli was found in concentration slightly higher than the legal limit only in the samples of December and January. In August, the E. coli concentration did not decrease during the depuration, while in the other samples significant reduction of E. coli concentration was observed. Salmonella spp. and V. parahaemolyticus were never detected in the clams harvested between March and September. Vibrio alginolyticus was found in the clams harvested in May and September both before and after the depuration process. 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. The meat yield was not influenced by the depurative treatment in C. gallina; the mean value found before depuration, 10.47% (with 1.95 SD), did not significantly vary after the treatment (10.58%, SD 2.07). In conclusion, the depuration conditions can improve the quality of C. gallina; however, its effects on microbiological quality depended on environmental conditions.