Chemical and nutritional characterization of non-conventional marine sources from the Atlantic coast of southwest Europe

This study aims to provide required data for the valorization of 24 underutilized seafood industry by-products, focusing on their proximate composition, amino acid and fatty acid profiles, mineral content, and nutritional indices. A total of 15 samples were from 5 species of fish: skipjack tuna ( Katsuwonus pelamis ), yellowfin tuna ( Thunnus albacares ), blue whiting ( Micromesistius poutassou ), horse mackerel ( Trachurus trachurus ) and turbot ( Scophthalmus maxima ). Another 4 biomasses were from mussels ( Mytilus galloprovincialis ), 1 sample from octopus ( Octopus vulgaris ), and finally 4 by-products were from different squid species ( Sepia officinalis, Dosidicus gigas, Illex argentinus and Loligo vulgaris ). Results indicated that protein are predominant across all samples, remarkably in yellowfin and skipjack tuna viscera (72.74% and 68.28%, respectively), tuna trim blend (72.65%) and blue whiting and horse mackerel head (68.03% and 60.40%, respectively). Leucine and lysine were identified as the most prevalent essential amino acids (EAA), with concentrations between 13.72%-25.86% and lysine between 10.27%-21.71% from total EAA. Additionally, EAA index (EAAI) identified yellowfin tuna trim blend (110%), squid gladius (105%), and squid viscera (102%) as EAA-rich by-products. Regarding fatty acids, turbot viscera and skipjack tuna head stood out as lipid-rich samples (51.32% and 38.56%, respectively) and squid viscera showed the highest EPA (27,572.10 ± 3,938.73 mg/kg) and DHA (42,770.63 ± 5,430.86 mg/kg) content. In conclusion, this work not only provides an overview of the nutritional profile of underutilized seafood industry by-products, but also remarks their subsequent valorization. Current market trends highlight a growing demand for proteins that are healthy (nutritious and well-balanced diets), sustainable (from environmental, economic and social perspectives) and ethically obtained. • Comprehensive nutritional profiling was conducted on 24 marine by-products • Several by-products exceeded 70% protein with excellent amino acid quality • Cephalopod viscera showed the highest EPA and DHA concentrations • Mussel shells, broths, and fish bones were rich in Ca, Fe, and Zn • Results support future sustainable valorization and industrial innovation