Does Dietary Lipid Level Affect the Quality of Triploid Rainbow Trout and How Should It Be Assessed?

Organoleptic properties and nutritional value are the most important characteristics of fish fillet quality, which can be determined by a series of quality evaluation indexes and closely related to fish nutrition. Systematic organoleptic and nutritional quality evaluation indexes consisting of 139 indexes for physical properties and chemical compositions of triploid rainbow trout were established. Besides, effects of dietary lipid levels (6.6%, 14.8%, 22.8% and 29.4%) on the quality of triploid rainbow trout were analyzed in the study. The main results showed that, for fillet appearance quality, fish fed diets with lipid levels above 22.8% had higher fillet thickness and redness but lower gutted yield and fillet yield (p p p p < 0.05). For nutritional value, a high lipid diet could increase the lipid nutrition level (such as the content of long chain polyunsaturated fatty acids increased from 3.47 to 4.41 g/kg muscle) but decease tryptophan and selenium content (from 2.48 to 1.60 g/kg muscle and from 0.17 to 0.11 g/kg muscle, respectively). In total, a high lipid diet could improve the quality of triploid rainbow trout. The minimum dietary lipid level for triploid rainbow trout should be 22.8% to keep the better organoleptic and nutritional quality