Inter-species variability in bivalve purification processes: Towards evidence-based optimization

Purification represents a critical post-harvest step in ensuring the suitability and the safety of bivalve molluscs intended for human consumption, as it enables reducing the microbial load potentially accumulated during harvesting. In this study, the effectiveness of a flow-through purification system in reducing concentrations of Escherichia coli was evaluated in five commercially relevant bivalve species: Mytilus galloprovincialis, Magallana gigas, Ruditapes philippinarum, Chamelea gallina, and Callista chione. A standardized contamination protocol was first developed to account for species-specific bioaccumulation kinetics, as short-term exposure experiments revealed marked variability in the uptake of E. coli. Using linear modelling and inverse prediction approaches, the contamination conditions required to obtain target bacterial loads in bivalves were estimated, allowing the achievement of concentration levels representative of Class B and Class C areas. Following this, a standardized experimental design was used to monitor species-specific microbiological clearance over 48 h of purification. Both log-linear regression and one-phase decay modelling were applied to describe microbial decline, enabling robust characterization of purification kinetics. Magallana gigas and Callista chione consistently showed the most rapid decreases in bacterial load (18 h of depuration to achieve safe levels under Class B conditions), whereas Chamelea gallina exhibited significantly slower purification. Overall, data indicate that applying uniform purification durations may lead to suboptimal or excessive treatments, depending on the species and initial contamination levels. Therefore, a shift towards species-specific purification strategies is warranted to ensure both food safety and environmental-economic sustainability, particularly when using flow-through purification systems, which offer significant operational advantages under appropriate physicochemical conditions.