In this survey a total of 107 tuna cans were collected between 2020 and 2022 from 7 different Portuguese commercial brands. Samples were purchased from main supermarket chains, large-scale distributors and local stores. Samples were categorised by the quarter of the year when the tuna was canned (inferred from the expiry date) with each sample was tested in triplicate. Extracted DNA was purified and iteratively tested using molecular metabarcoding methods.
The researchers report (open access) that the occurrence of different species was observed only in products canned in brine or water (i.e. all products canned in oil were Skipjack Tuna). Skipjack tuna was predominant across all canning liquids and brands analysed. Nonetheless, other species like Thunnus obesus and T. albacares, or Auxis spp. (not considered true tuna) were also detected. The use of different species was limited to cans produced during the second quarter of the year, which could reflect differences in seasonal availability of different tuna species or in sourcing strategies/market preferences of each company. For four brands, multiple species were detected inside the same can. This violates current European legislation.
The researchers conclude that these results provide the first broad assessment of species used in the Portuguese tuna canning industry and showed the inclusion of vulnerable species is limited.
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