The effect of dietary vitamin E and C level on market-size turbot (Scophthalmus maximus) fillet quality

Fish fillet quality has been shown to be influenced by the level of antioxidants in preslaughter diet. Thus, an experiment was conducted to study the effect of different levels of vitamin E and C on the fillet quality of market-size reared turbot (Scophthalmus maximus). Turbot of a mean initial weight of 347 +/- 20 g were divided into four groups and fed commercial turbot diets (60% protein, 12% fat), supplemented with alpha-tocopheryl acetate (mg kg (-1)) and ascorbyl-2 monophosphate (mg kg (-1)) at the following dietary levels: 500/100, 1000/100, 100/1000, 100/100 respectively. Over a dietary supplementation period of 15 weeks, fish were fed to satiation and reached a final mean weight of 916 +/- 29 g. alpha-Tocopherol levels increased significantly (P < 0.001) in tissue (i.e. muscle, liver, heart and kidney) of fish fed diets containing elevated levels of alpha-tocopheryl acetate. In ice storage, fillets of these fish exhibited significantly lower (P < 0.001) levels of lipid oxidation, and showed significantly less (P < 0.001) colour deterioration (higher hue angle and lower chroma). Elevated dietary alpha-tocopheryl acetate levels had a negative effect (P less than or equal to 0.001) on the concentration of ascorbic acid in muscle tissue. An increase in dietary vitamin C did not have any detectable effect on fillet quality. Prolonged feeding times had a negative effect on lipid oxidation (P < 0.001) and colour deterioration (P < 0.01). These results suggest that increased dietary alpha-tocopheryl acetate could prevent colour deterioration and lipid oxidation of turbot fillets in retail storage on ice.