Muscle carotenoid content and colour of farmed rainbow trout fed astaxanthin or canthaxanthin as affected by cooking and smoke-curing procedures

Summary. Carotenoids and colour characteristics were studied in raw, steamed and smoke-cured muscle of rainbow trout fed synthetic astaxanthin (50 or 100mgkg-1 diet) or canthaxanthin (100mgkg-1 diet) for 15 months. In raw muscle main carotenoid concentration was strongly correlated with hue, chroma, and lightness. Diet and sex effects were significant on most traits, with little or no interaction. Female muscles contained much more carotenoid and were more coloured than male ones. Astaxanthin fed fish were more red than canthaxanthin fed fish. Significant mean effects of cooking were an apparent increase of carotenoid concentration and an increase of lightness. Hue and chroma were practically unchanged with high correlations between raw and cooked muscle measurements. Lightness increased and differences between sexes and individuals were reduced. Smoke-curing induced an increase of carotenoid concentration and a decrease of hue and lightness. Hue of canthaxanthin fed fish when smoke-cured was similar to that of raw fish fed astaxanthin. Lightness, still dependant on that of the raw muscle, was reduced and differences among diets, sexes and individuals were reduced.