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Tuna cans are relevant seafood products for which mixtures of different tuna species are not allowed according to European regulations. In order to support the prevention of food fraud and mislabelling, a next-generation sequencing methodology based on mitochondrial cytochrome b and control region markers has been tested. Analyses of defined mixtures of DNA, fresh tissue and canned tissue revealed a qualitative and, to some extent, semiquantitative identification of tuna species. While the choice of the bioinformatic pipeline had no influence in the results (p = 0.71), quantitative differences occurred depending on the treatment of the sample, marker, species, and mixture (p < 0.01). The results revealed that matrix-specific calibrators or normalization models should also be used in NGS. The method represents an important step towards a semiquantitative method for routine control of this analytically challenging food matrix. Tests of commercial samples uncovered mixed species in some cans, being not in compliance with EU regulations.

Seafood authenticity is a key parameter for seafood quality, particularly in Europe where regulations provide a strict framework for seafood labeling. A wide variety of methods are commonly used in control laboratories (private or public) to identify seafood species, but emergent approaches for the development of new and fast DNA- and protein-based methods for species differentiation are also considered. To address the challenges in controlling further labeling requirements in the latest European legislation on seafood product traceability and labeling (Regulation (EU) 1379/2013), a review of the development of methods to identify fishing areas and to distinguish between wild and farmed fish, as well as an overview of the advanced methods that could be used for differentiation of fresh and frozen-thawed fish, is given. These methods will become increasingly important in the near future as the risk-based control of food authenticity is prescribed by the new EU control regulation (Regulation (EU) 2017/625)

Conventional Sanger sequencing of PCR products is the gold standard for species authentication of seafood products. However, this method is inappropriate for the analysis of products that might contain mixtures of species, such as tinned tuna. The purpose of this study was to test whether next-generation sequencing (NGS) can be a solution for the authentication of mixed products. Nine tuna samples containing mixtures of up to four species were prepared and subjected to an NGS approach targeting two short cytochrome b gene (cytb) fragments on the Illumina MiSeq platform. Sequence recovery was precise and admixtures of as low as 1% could be identified, depending on the species composition of the mixtures. Duplicate samples as well as two individual NGS runs produced very similar results. A first test of three commercial tinned tuna samples indicated the presence of different species in the same tin, although this is forbidden by EU law