Pigmentation of juvenile coho salmon with carotenoid oil extracted from Antarctic krill

Abstract

Pigmentation of the flesh of juvenile coho salmon ( Oncorhynchus kisutch) in fresh water was investigated by feeding diets supplemented with an oil extracted from Antarctic krill ( Euphausia superba). The oil contained ( 3R,3′R)-astaxanthin diester as a main carotenoid. Small fish (80 g) fed the supplemented diet showed very little flesh pigmentation. However, marked pigmentation was observed when fish with an initial weight of approximately 180 g were reared on diets containing 7.2 mg astaxanthin 100 g diet for 4 weeks. The carotenoid content of flesh was about 0.2 mg 100 g and it consisted almost exclusively of astaxanthin. Fish fed a diet containing krill oil for 8 weeks retained most of the carotenoids laid down in the flesh throughout a following 24-week period on a non-carotenoid diet. Structural isomer composition of astaxanthin in the flesh of fish fed a diet containing 14.4 mg astaxanthin 100 g was 93, 4–5 and 2–3% for all- trans-, 9- cis- and 13- cis-astaxanthin at the end of the experiment, respectively. Optical isomer composition of the all- trans-astaxanthin fraction was 74, 10 and 16% for ( 3R,3′R)-, ( 3S,3′R) meso- and ( 3S,3′S)-astaxanthin, respectively. No isomerization of astaxanthin deposited in the flesh was found.