Wakamatsu, K.; Dijkstra, J.M.; Mørkøre, T.; Ito, S. Eumelanin Detection in Melanized Focal Changes but Not in Red Focal Changes on Atlantic Salmon (Salmo salar) Fillets. Int. J. Mol. Sci.2023, 24, 16797.
Wakamatsu, K.; Dijkstra, J.M.; Mørkøre, T.; Ito, S. Eumelanin Detection in Melanized Focal Changes but Not in Red Focal Changes on Atlantic Salmon (Salmo salar) Fillets. Int. J. Mol. Sci. 2023, 24, 16797.
Wakamatsu, K.; Dijkstra, J.M.; Mørkøre, T.; Ito, S. Eumelanin Detection in Melanized Focal Changes but Not in Red Focal Changes on Atlantic Salmon (Salmo salar) Fillets. Int. J. Mol. Sci.2023, 24, 16797.
Wakamatsu, K.; Dijkstra, J.M.; Mørkøre, T.; Ito, S. Eumelanin Detection in Melanized Focal Changes but Not in Red Focal Changes on Atlantic Salmon (Salmo salar) Fillets. Int. J. Mol. Sci. 2023, 24, 16797.
Abstract
Superficial discolored spots on Atlantic salmon (Salmo salar) fillets are a serious quality problem for commercial seafood farming. Previous reports proposed that the black spots (called melanized focal changes (MFC)) may be melanin, but no convincing evidence has been reported. In this study, we performed chemical characterization of MFC, and also of red pigment (called red focal changes (RFC)), of salmon fillets using alkaline hydrogen peroxide oxidation and hydroiodic acid hydrolysis. This revealed that the MFC contain 3,4-dihydroxyphenylalanine (DOPA)-derived eumelanin whereas the RFC only contain trace amounts of eumelanin. Therefore, probably, the black color of MFC can be explained by the presence of eumelanin from accumulated melanomacrophages. For the red pigment, we could not find a significant signature of either eumelanin or pheomelanin, and the red color is probably predominantly hemorrhagic in nature. However, we found that in RFC the level of pigmentation did increase together with some melanogenic metabolites. Comparison with a “mimicking experiment,” in which a mixture of a salmon homogenate + DOPA was oxidized with tyrosinase, suggested that the RFC include conjugations of DOPAquinone and/or DOPAchrome with salmon muscle tissue proteins. In short, the results suggest that melanogenic metabolites in MFC and RFC derive from different chemical pathways, which would agree with the two different colorations deriving from distinct cellular origins, namely melanomacrophages and red blood cells, respectively.
Keywords
Atlantic salmon; Melanized focal changes; Red focal changes; Eumelanin; Pheomelanin; PTCA; 4-AHP; AHPO; Melanomacrophages; Red blood cells
Subject
Biology and Life Sciences, Biochemistry and Molecular Biology
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
