New approach for vitamin E extraction in rainbow trout flesh: Application in fish fed commercial and red seaweed‐supplemented diets

A vitamin E extraction method for rainbow trout flesh was optimized, validated, and applied in fish fed commercial and Gracilaria vermiculophylla ‐supplemented diets. Five extraction methods were compared. Vitamers were analyzed by HPLC/DAD/fluorescence. A solid‐liquid extraction with n ‐hexane, which showed the best performance, was optimized and validated. Among the eight vitamers, only α‐ and γ‐tocopherol were detected in muscle samples. The final method showed good linearity (>0.999), intra‐ (<3.1%) and inter‐day precision (<2.6%), and recoveries (>96%). Detection and quantification limits were 39.9 and 121.0 ng/g of muscle, for α‐tocopherol, and 111.4 ng/g and 337.6 ng/g, for γ‐tocopherol, respectively. Compared to the control group, the dietary inclusion of 5% G. vermiculophylla resulted in a slight reduction of lipids in muscle and, consequently, of α‐ and γ‐tocopherol. Nevertheless, vitamin E profile in lipids was maintained. In general, the results may be explained by the lower vitamin E level in seaweed‐containing diet. Practical Applications: Based on the validation results and the low solvent consumption, the developed method can be used to analyze vitamin E in rainbow trout. The results of this work are also a valuable information source for fish feed industries and aquaculture producers, which can focus on improving seaweed inclusion in feeds as a source of vitamin E in fish muscle and, therefore, take full advantage of all bioactive components with an important role in fish health and flesh quality. Muscle samples from rainbow trout fed a commercial diets were used to select, optimize, and validate an extraction method for vitamin E. The final method was used to extract α and γ‐tocopherol in muscle from rainbow trout fed a control (CTRL) and a seaweed‐supplemented diet (GRA).