Determination the changes of E. coli depuration times in Ruditapes decussatus and Venus verrucosa by production area and species differences

Abstract

In this study, two important economic bivalve mollusc species, grooved carpet shell (Ruditapes decussatus) obtained from two different production areas (batch-A and batch-B) and warty venus (Venus verrucosa) were contaminated with Escherichia coli (E. coli), and the time-dependent changes in their ability to depuration process were determined.  At the same time, after the natural E. coli levels of these two species were determined, the natural depuration times were also investigated by subjecting them directly to depuration process separately.

The natural E. coli loads of the carpet shell and warty venus samples used in the research were determined as 1500 MPN/100 g in batch-A samples, 430 MPN/100 g in batch-B samples while the level was determined as 74 MPN/100 g warty venus samples. The natural sample depuration process was completed 18 hours after the start of the process for batch-A samples and 6 hours after the start of the process for batch-B and warty venus samples, and it was determined that the products reached Class A production area standards. Depuration time of samples after the contamination of samples with E. coli at the level of 2900 MPN was determined as 12 hours for warty venus, 18 hours for carpet shell. As for the samples contaminated at the level of 4600 MPN, carpet shell (batch-A) and warty venus samples reached the Class A production area standards after 24 hours and warty venus (batch-B) samples reached the Class A production area standard after 48 hours. As a conclusion, species, and sample collection sites may have effect on depuration characteristics of E. coli and this may be related to physiological conditions of the specimens during the collection sites.