Amino acid and bioactive signatures of yellowfin tuna loins: ocean-specific patterns across major fishing grounds

Background Tunas are among the most valuable and consumed fish worldwide. In 2022, global tuna landings reached 8.3 million tonnes, with Yellowfin tuna ( Thunnus albacares ; YFT) representing 18.8% of the total, and ranking fifth among the most landed finfish. This study tested three null hypotheses: H01: Total protein content and the amino acid composition do not vary between geographic origin; H02: Bioactive compound profiles do not differ among regions; H03: There are no compositional differences that allow discrimination of tuna by oceanic origin. Methods Sixty loins (20 per ocean) were analyzed for total protein content (Kjeldahl), AA profile (by fluorescence detection), and bioactive molecules (by HPLC-UV/Vis). Results Protein content (25.3 g/100 g) and general AA composition confirmed H 01 , though 11 of 17 AAs differed ( p < 0.05). Bioactive compounds were mostly similar (H 02 ), with higher anserine and creatine in Indian Ocean fish. Essential AA indices remained high across samples. Conclusion YFT loins showed consistent total protein content (25.3 g/100 g of edible portion), supporting a ‘high-protein’ nutritional claim, and confirming that protein content and overall amino acid (AA) profile do not differ significantly among specimens from different oceans (H01). Likewise, muscle bioactive compounds were generally comparable across origins (H02), indicating that AA signatures and bioactive compound levels cannot reliably trace geographic origin.