Feed ration prior to slaughter -: a potential tool for managing product quality of Atlantic salmon (Salmo salar)

During a 110-day winter period, five duplicated groups of 50 Atlantic salmon (3.9 kg initial weight) were fed 0.0, 0.25, 0.5, 0.75 and 1.0 times maximum feed intake before slaughter with the purpose of studying body composition and quality related characteristics in raw and smoked salmon fillets. Final weights increased linearly with feed ration from 3.5 to 4.9 kg at ration 0.0 and 1.0, respectively. Decreasing feed ration resulted in a slimmer body shape (i.e., lower condition factor), increased carcass-yield and decreased fillet-yield, and decreased fillet fat content. Al though fillet protein content was not significantly affected by ration level, the percent of water-soluble proteins in white muscle was increased by feed ration. Decreased content of free and increased content of protein-bound hydroxyproline in white muscle was found with increasing feed ration. White muscle pH, in post-rigor state, but not at slaughter, decreased with increasing ration level, reflecting in vivo glycogen and post-rigor lactate levels. After filleting, a significant increase of fillet gaping was found with increasing ration. Sensory analyses of smoked fillets revealed that fatness, juiciness and coarseness increased, whereas hardness decreased with increasing feed ration. Further, acidulous flavour and odour in smoked fillet increased significantly. Despite an increased astaxanthin content in raw fillet, the sensory scores for colour intensity decreased and whiteness increased with increasing feed ration. Consequently, reduced ration before slaughter can be a tool for improving slaughter-yield, reducing fat content and gaping in raw fillet, slightly improving colour intensity and changing textural properties of smoked fillet. The costs in terms of lost weight and less fillet-yield will, however, be substantial. (C) 1999 Elsevier Science B.V. All rights reserved.