MYCOLab Ai Logo - gold and army green

Eumelanin Detection in Melanized Focal Changes but Not in Red Focal Changes on Atlantic Salmon (Salmo salar) Fillets

Summary

Farmed Atlantic salmon sometimes develop unsightly black and red spots that reduce market value. Researchers analyzed these discolored areas and found that the black spots contain a type of melanin pigment (eumelanin) produced by immune cells called melanomacrophages. The red spots contain different compounds formed from oxidized proteins rather than true melanin. Understanding the chemical differences between these two types of spots could help salmon farmers develop better prevention strategies.

Background

Superficial discolored spots on Atlantic salmon fillets represent a major quality problem in commercial seafood farming. Black spots (melanized focal changes) and red spots (red focal changes) appear on farmed salmon, with increasing prevalence over time, but their chemical composition has not been thoroughly characterized.

Objective

To chemically characterize melanized focal changes (MFCs) and red focal changes (RFCs) in Atlantic salmon fillets using alkaline hydrogen peroxide oxidation and hydroiodic acid hydrolysis to determine whether these discolorations contain melanin and identify the type of melanin present.

Results

MFCs contained significant levels of DOPA-derived eumelanin, particularly DHICA-rich eumelanin, while RFCs contained only trace amounts of eumelanin or pheomelanin. RFCs showed elevated levels of melanogenic metabolites including HI-DOPA and protein-bound 5-cysteinyldopa, suggesting protein conjugations of DOPAquinone and DOPAchrome.

Conclusion

The pigment in MFCs is DOPA-derived eumelanin from melanomacrophages, while RFCs contain oxidized proteins produced by DOPAquinone and/or DOPAchrome binding to salmon muscle proteins. MFCs and RFCs derive from distinct chemical pathways and cellular origins, with different prevention strategies likely needed for each.
  • Published in:International Journal of Molecular Sciences,
  • Study Type:Analytical Research Study,
  • Source: PMID: 38069120, DOI: 10.3390/ijms242316797
Scroll to Top