Fillet shelf-life of Atlantic halibut Hippoglossus hippoglossus L. fed elevated levels of α-tocopheryl acetate

Fish fillet quality may be influenced by the antioxidant level in preslaughter diet. Thus, the effects of dietary alpha-tocopheryl acetate supplementation and feeding time on the flesh quality of farmed Atlantic halibut Hippoglossus hippoglossus L. were investigated. Halibut of mean initial weight of 312 +/- 12.3 g were divided into two groups and fed commercial diets, supplemented with different levels of alpha-tocopheryl acetate at the dietary inclusion levels of 189 and 613 mg kg(-1) diet. Fish were sampled after 6,9,12 and 24 weeks. Over the experimental period, they reached a final mean weight of 1320 +/- 108.4 g. Tissue alpha-tocopherol of fillet and liver was significantly affected by the levels of alpha-tocopheryl acetate given with the diets (P < 0.001). In storage on ice, fillets of fish fed the diets high in α-tocopheryl acetate exhibited significantly lower (P < 0.001) levels of lipid oxidation. The colour of fillets in all groups deteriorated slightly, but diet did not affect this process. Halibut fed the supplemented diets for longer periods were better protected against lipid oxidation (P < 0.001) and colour deterioration (P < 0.01) than those fed for shorter periods. However, after 9 days of storage, lipid oxidation levels were still extremely low [< 0.6 μg malondialdehyde (MDA) g(-1) fillet], even in fillets of fish fed the low α-tocopheryl acetate diet for a short period preslaughter. Different slaughtering methods tested at the end of the trial showed that percussive stunning can delay the onset of rigor mortis by 8-12 h compared with bleeding of the fish. These results suggest that halibut fillets have enhanced shelf-life stability even at low doses of dietary α-tocopheryl acetate, and that other factors in the antioxidant defence mechanisms of the species might play a major role in the prevention of lipid oxidation.