This study (IAFP membership or purchase required) investigated whether there are environmental (i.e. non-adulterations) explanations for foreign tuna DNA in canned tuna. It was prompted by reports that DNA of undeclared tuna species had been found in cans labeled as skipjack. Only one species of tuna is allowed in a can sold in the European Union if the muscle structure of the tuna is visible.
Previous reports had identified environmental DNA (eDNA) from various Thunnus and other species in the ocean and on the tuna catcher vessels and further tracked to the first stage of raw tuna processing in tuna canning (thawing).
The authors built on this work to further investigate if eDNA can be found in other parts of the cannery supply chain during tuna processing in the stages after thawing.
They collected 99 samples from raw/frozen and unfrozen tuna, precooked tuna, and retorted (heat preserved) tuna. A total of 225 DNA analyses were performed on these samples using Polymerase Chain Reaction (PCR) methods and Sanger sequencing, real-time PCR and NGS-SBS.
They report that DNA fragments from other tuna species are present during tuna harvesting and processing operations. They suggest that eDNA from various Thunnus and other species could be found at multiple levels of the cannery processing chain.
They conclude that their results highlights the drawbacks of using traditional DNA barcoding for the purpose of detecting fraud or mislabeling with retorted canned tuna. They present mitigation measures for solving the problem of multiple species of muscle meat in tuna products during the canning process.
Photo by Dillon Lobo on Unsplash
