News

Given the diversity of traded bivalve molluscs (scallops, oysters, mussels etc), broad taxonomic coverage is essential for untargeted screening to verify species authenticity. 

To address this challenge, the authors of this paper (open access) developed and validated a DNA metabarcoding approach employing two PCR assays, a singleplex and a duplex, to amplify mitochondrial 16S rDNA fragments (160–203 bp) across seven families: Ostreidae, Pectinidae, Mytilidae, Pharidae, Veneridae, Glycymerididae, and Cardiidae.

Taxa were identified at the species or genus level in 38 reference samples and four model food samples, with individual species detected at concentrations as low as 0.008–0.014% (w/w).

They report that all main and most minor components were detected in 40 DNA extract mixtures, with a small number of false negatives which they hypothesise result from primer-template mismatches causing amplification bias.

In a follow-up surveillance exercise they tested 70 commercial food products. They concluded that 29% of samples were mislabeled (either adulteration or substitution), with scallops being the most frequently affected family.

They conclude that the method is suitable for detecting species substitution and adulteration. This study presents the first DNA metabarcoding method targeting a broad taxonomic range of bivalves. The validated approach is particularly-suited for qualitative screening in routine food authentication and can support laboratories and regulatory agencies in enforcing international monitoring strategies.

Thanks to FAN member, and author, Julia Andronache for flagging this paper.  If you have a publication that it would be useful to share with our members then please get in touch.

Shellfish harvesting is highly regulated in most countries, including the UK.  Harvest areas are opened or closed by regulatory authorities depending on water quality and potentially toxic algal blooms.  Illegal harvesting from closed areas puts consumers at risk as they can carry E coli, norovirus or be contaminated with high levels of toxic chemicals..  It is a perennial problem and previous incidents have involved large-scale organised crime.

A recent crackdown by authorities (the council, Sussex Police, Food Standards Agency, National Food Crime Unit, Inshore Fisheries and Conservation Authority and Gangmaster Labour Abuse Authority) on the English South Coast led to the seizure of illegally harvested shellfish.

This case was part of Operation Pearl and involved months of covert investigations had taken place to understand how the illegally harvested shellfish were reaching food businesses and consumers.