The effects of dietary α-tocopherol and oxidised lipid on post-thaw drip from catfish muscle

DL-α-tocopheryl acetate was added at different concentrations (20 or 100 mg kg−1) to catfish diets containing either fresh or oxidised (rancid) oil to determine the effects on tissue α-tocopherol levels, fatty acid composition and post-thaw exudative moisture loss from fillets of African catfish (Clarias gariepinus). ing a 56-day feeding trial in which duplicate groups of twenty 15.7-g catfish were fed diets at a ration level of 3% body weight per day, it was recorded that for any given oil status, muscle α-tocopherol responded significantly (P < 0.05) to elevations in dietary DL-α-tocopheryl acetate. Oil quality exerted a profound effect on muscle α-tocopherol levels, with fillets from fish fed oxidised diets exhibiting significantly (P < 0.05) lower α-tocopherol concentrations, despite similar dietary tocopherol-ester contents. Decreased PUFA content was recorded in fillets from fish fed rancid-oil diets, although dietary α-tocopherol was successful in lessening the effect. haw exudative moisture losses from fillets after refrigerated storage for 48 h was significantly (P < 0.05) greater in treatments fed oxidised-rather than fresh-oil diets. Within the oxidised treatments, elevated dietary α-tocopheryl acetate inclusion resulted in a lessening of the moisture loss, thus demonstrating the protective effect of vitamin E against freeze damage of muscle-tissue membranes. After 96 h, the significant differences (P < 0.05) in exudative losses between treatments was solely due to muscle α-tocopherol concentration. Hence, α-tocopherol was shown to be the most important factor in the maintenance of post mortem membrane stability. s investigation supplemental dietary vitamin E afforded some degree of protection to Clarias tissues, against the stresses involved with the consumption of rancid feeds.