How does feed with different levels of vegetable origin affect the sensory quality of ice storage Rainbow trout (Oncorhynchus mykiss)?

Background Fish from the aquaculture sector make up a steep raising share of the total fish consumed and play in that respect an essential role. The most important farmed fish in Denmark is rainbow trout (Oncorhynchus mykiss). However the aquaculture sector, raising fish species which are primarily carnivores, is facing major challenges as a consequence of the limited access in future sustainable resources of wild fish or other sea living organisms from a lower trophic level for feed production. Consequently, alternative feeding regimes are now considered e.g. use of components of vegetable origin such as soy oil or rapeseed oil combined with vegetable proteins. Such a change in feeding regime will result in a “green fish” and may affect flesh quality and eating quality. The objective was to study the effect of vegetable based feed on sensory of ice storage farmed rainbow trout. Experimental design and methods Feed trials Rainbow trout were farmed in tanks at Biomar A/S, Hirtshals and fed on six different diets covering only marine, only vegetables and mixture of marine and vegetable feeds. Trout for the quality study were slaughtered, vacuum-packed and stored at -80°C until analysis. Sensory Quality Changes in sensory quality were determined by objective descriptive sensory methods using profiling carried out by a trained panel. The fish samples were thawed and ice storage for 3, 5, 7 and 12 days. Results The sensory characterization of the trout feed with 100% marine and 100% vegetable feed showed after 3 days of ice storage that the trout feed with marine fed were more firm, juicy and the texture was more flacky that trout feed with vegetable feed. This sensory difference increased with increasing ice storage.