Influence of alpha-tocopherol acetate on the short- and long-term storage properties of fillets from Atlantic salmon Salmo salar fed a high lipid diet

During refrigeration, lipid oxidation is a major factor contributing to pos t-mortem deterioration of flesh quality. Polyunsaturated fatty acids (PUFA) , especially n-3 PUFA, are present in high concentration in fish tissues, a nd in oils used in diets, and are readily susceptible to peroxidation. alph a-Tocopherol (AT) can reduce tissue lipid peroxidation in vivo and post mor tem. The effect of increasing the tissue level of AT by dietary supplementa tion of alpha-tocopherol acetate (ATA) was therefore investigated. Commerci al salmon diets C, M and H, high in lipids, containing 184, 573 and 565 mg ATA kg(-1) diet DM (dry matter) were fed to 18 fish per treatment. Dietary AT: PUFA ratios were 2.0, 6.3, and 9.5 mg g(-1) for diets C, M and H, respe ctively. Fish (mean initial live weight 630 g) were slaughtered after 50 an d 78 days of feeding. Fillet samples were analysed fresh or after storage a t 4 degrees C for 12 days and -20 degrees C for 12 months. Lipid oxidation was measured using the thiobarbituric acid test. Colour score, but not caro tenoid content, of fillets was significantly higher between 6 and 12 days o f fresh storage in fish fed diets M and H compared with those fed diet C. C olour score, carotenoid content and AT content decreased and the content of lipid oxidation products increased following storage of fillets at -20 deg rees C for up to 12 months, although lipid oxidation was always significant ly lower in fish fed diets M and H.