The effect of dietary antioxidants on hyperpigmented fillet spots of Atlantic salmon (Salmo salar L.)

M-AA

إنجليزي. Superficial discolored spots on Atlantic salmon fillets is a serious problem for the farmingindustry. Fillets with large dark stained spots are downgraded by the processing industrywhile smaller spots are removed, requiring extra labour. The main aim of the present studywas to investigate the effect of diet on appearance, location and size of dark stained spots.The fish used were Atlantic salmon (Salmo salar L.) fed a standard commercial feed (Control)or the same feed added antioxidants (vitamin C, E and selenium) (Antioxidant). Theexperiment was carried out from 7th January to 13th March 2015. The results showed thatthe supplementation of antioxidants had no significantly effect on growth (average bodyweight 4 kg) or other biometric traits, but improved the fillet quality. Significantly loweroccurrence of spots (31% vs. 45%), lower number of dark stained muscle segments (1.4 vs.2.3), smaller fillet spot size (0.6 vs. 2.2 score) and lower fillet gaping score (0.8 vs. 1.0) werefound of the Antioxidant group as compared to the Control group. Results showed that themelanin (40%) and a combination of melanin and scar (25%) were dominating the visualappearance of spots. Colorimetric analysis of the dark stained spots of the Antioxidant grouprevealed paler (higher L* value), less redness (lower a* value) and less yellowness (lower b*value) as compared to the Control group. Colorimetric characteristics of the dark spots werestable during one week of ice storage. Image analysis showed significantly higher lightness(higher L* value), less yellowness, larger area and wider width of myocommata of theAntioxidant group compared with the Control group. It is concluded that dietarysupplementation of antioxidants reduced fillet gaping, occurrence of dark spots, spots sizeand number of dark stained muscle segments significantly.