EFFECT OF DIETARY VITAMIN-E LEVELS ON OXIDATIVE STABILITY OF TROUT FILLETS

Rainbow trout weighing about 150 g were allocated to four dietary treatments (0, 50, 100, and 200 IU of supplemental vitamin E/kg feed). Pooled samples were taken after 29, 57 and 85 days (end of experiment) for analysis of α-tocopherol levels in plasma, liver and fillet. On day 85, the pooled samples from each dietary treatment were tested under forced oxidative conditions for generation of thiobarbituric acid (TBA) reactive compounds, expressed as equivalents of malondialdehyde (MDA). Furthermore, organoleptic tests to determine differences and preferences between the fillets of trout fed the different dietary treatments were performed. Levels of α-tocopherol in plasma, liver and fillet were directly related to dietary vitamin E levels. The quantity and characteristics of lipids were not influenced by vitamin E. A pronounced dependency of the measured MDA values on the dietary vitamin E level as well as on the α-tocopherol level in fillet was found. This strongly indicates that dietary supplementation of vitamin E effectively stabilized lipids in trout fillet. The relevance of these findings was underlined by the organoieptic tests which established significant differences between the dietary treatments; all significant preferences were for fillets with the higher vitamin E levels. © 1990.