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RESULTS. REFERENCES. ABSTRACT. OBJECTIVES. CONCLUSION. INTRODUCTION. MATERIALS AND METHODS. Effects of Dietary Alpha-tocopheryl Acetate on Lipid Oxidation of Omega-3-enhanced Farmed Rainbow Trout ( Oncorhynchus mykiss ). Y. C. Chen, J. Nguyen, K. Semmens, S. Beamer, and J. Jaczynski

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  1. RESULTS REFERENCES ABSTRACT OBJECTIVES CONCLUSION INTRODUCTION MATERIALS AND METHODS Effects of Dietary Alpha-tocopheryl Acetate on Lipid Oxidation of Omega-3-enhanced Farmed Rainbow Trout (Oncorhynchus mykiss) Y. C. Chen, J. Nguyen, K. Semmens, S. Beamer, and J. Jaczynski West Virginia University, Animal & Veterinary Sciences This experiment was a full factorial design (9 treatments). A commercial trout diet was supplemented with 0, 8.5, or 15% (w/w) of flaxseed oil (FO) and 0, 300, or 1500ppm of alpha-tocopheryl acetate (α-TA). Trout were harvested on days 0, 30, 60, 90, and 120. Trout were filleted to obtain boneless, skinless butterfly fillets. Total fat and alpha-tocopherol contents, as well as thiobarbituric acid reactive substances (TBARS) values of fillets were measured immediately following the fish harvest. Regardless of supplementing trout diets with FO and α-TA, no (P>0.05) differences of the total fat contents and TBARS values in trout fillets were measured. The highest (P<0.05) alpha-tocopherol content in fillets was only observed when supplementing trout with 1500ppm of α-TA for 120 days. No effects of retarding oxidation in trout fillets when supplementing trout with FO and α-TA might be due to the freshness of the fillets and a slow cumulative effect of α-TA in trout fillets. Our results indicate that lipid oxidation of omega-3-enhanced trout fillets cannot be reduced by supplementing trout diets with α-TA. Therefore, the synergetic effect of other antioxidants and anaerobic conditions with α-TA on the reduction of lipid oxidation in omega-3-enhanced trout fillets should be investigation. We also conducted storage stability study using the omega-3-enhanced fillets. The overall objective was to investigate the effects of α-TA supplementation on lipid oxidation of omega-3-enhanced trout fillets. Table1. Fat (%) and TBARS of trout fillets as affected by feed supplemented with flaxseed oil and alpha-tocopheryl acetate Table2. alpha-tocopherol content (mg/kg meat) of trout fillets as affected by feed supplemented with flaxseed oil and alpha-tocopheryl acetate FO: flaxseed oil; α-TA: alpha-tocopheryl acetate FO: flaxseed oil; α-TA: alpha-tocopheryl acetate No differences were observed between the groups within a row (P>0.05) Flaxseed oil (FO) contains high concentration of alpha-linolenic acid (α-LNA), which is an omega-3 fatty acid (ω-3 FA). The American Heart Association suggests fish consumptions that are high in ω-3 FA at least twice a week. Hence, the FO may be used to supplement trout diets to increase ω-3 FA content in fillets. However, the ω-3 FA is unsaturated, and therefore, susceptible to oxidation. Hence, supplementing trout diets with an antioxidant may decrease the lipid oxidation of fillets. Castell and others (1972) reported that supplementing fingerlings with linoleic (18:2ω-6) and linolenic (18:3ω-3) fatty acids increased the concentration of these fatty acid and that of EPA and DHA in the muscle tissues. However, they did not determine the effects of the increased concentration of polyunsaturated fatty acid (ω-3 PUFA) on lipid oxidation or human health. Chaiyapechara and others (2002) designed the fish diets supplemented with vitamin E at 300 and 1500 mg of dl--tocopheryl acetate per kg of feed. Sensory analysis of trout fillets obtained from fish fed diets with 30% of lipids and 300 mg/kg of vitamin E showed off-flavor, which was correlated with such flavor attributes as fishy, musty, sour, and bitter. The dl--tocopheryl acetate at 1500 mg/kg of feed reduced the rate of lipid oxidation and the formation of undesirable off-flavors. Our hypothesis is that supplementing alpha-tocopheryl acetate (α-TA) into fish diet containing high concentration of FO can reduce the lipid oxidation of omega-3-enhanced farmed rainbow trout fillets. • Regardless of feeding period, total fat level (%) and TBARS values of trout fillets were not (P>0.05) affected by supplementing trout basal diet with flaxseed oil and alpha-tocopheryl acetate. • Supplementing rainbow trout with flaxseed oil and alpha-tocopheryl acetate does not (P>0.05) alter alpha-tocopherol content in trout fillets until 90 days. • However, after 120 days of feeding, the highest (P<0.05) alpha-tocopherol content in trout fillets was observed when supplementing trout with a 1500ppm of alpha-tocopheryl acetate. • Hence, no cumulative effect on alpha-tocopherol contents of trout fillets in different treatments until 90 days of feeding and freshness of trout fillets might be attributed to non-differences of TBARS values of trout fillets among treatments. • FO: flaxseed oil; α-TA: alpha-tocopheryl acetate • Test parameters: total fat content, alpha-tocopherol contents, and thiobarbituric acid reactive substrances value. Fig 1: Alpha-tocopherol content of trout fillets as affected by supplementing trout with alpha-tocopheryl acetate Castell JD, Lee DJ, Sinnhuber RO. 1972. Essential fatty acids in the diet of rainbow trout (Salmo gairdneri), lipid metabolism and fatty acid composition. J Nutr 102:93-100. Chaiyapechara S, Casten MT, Hardy RW, Dong FM. 2002. Supplementing high lipid rainbow trout feeds with vitamin E minimizes the off flavors and lipid oxidation in fillets. Abstract # 56-5. Presented at the IFT annual meeting (Anaheim, CA). June 15-19

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