Levels of biotoxins, heavy metals, and cytotoxicity of underutilized seafood by-products from the Atlantic Coast of Southwest Europe

Despite the trend of fish by-products valorisation, only a few studies address their toxicity. In most cases, these studies have been hindered by the lack of specific legislation regulating the suitability and safety of new applications. This work aims to carry out the analysis of two important families of contaminants, biotoxins and heavy metals, as well as cytotoxicity studies (HepG2 and Caco2 cell lines), in 24 fish, mussel, and cephalopod non-conventional by-products from the fishing industry. All samples were within legal limits for marine biotoxins, though mussel broken viands and squid viscera contained low levels of lipophilic marine toxins, mainly okadaic acid (OA). Analysis of mercury (Hg), lead (Pb), cadmium (Cd), and arsenic (As) by ICP-MS showed that the content of Hg (< 0.75 mg/kg) and Pb (< 0.90 mg/kg) is safe in all by-products. Cd was high in three samples, skipjack tuna viscera (9.574 mg/kg), yellowfin tuna viscera (14.8 mg/kg), and squid viscera (59.8 mg/kg) and As was especially high in squid and octopus cooking broths (13.66 and 92.91 mg/kg, respectively), and squid viscera (22.85 mg/kg). However, by-products will be transformed and diluted in other products, which will have to be analyzed for these heavy metals in the final product. Legislation and monitoring of these contaminants are essential to ensure the safety of the final consumer. To the best of our knowledge, this is the first report of OA toxins in squid by-products. This work provides information to improve the legislation on marine by-products.