evaluation of α-tocopherol acetate, peel and extract pomogrante antioxidative potential in diet contained fish oil on meat quality boiler chicken

introduction poultry meat enriched with long-chain polyunsaturated fatty acids n-3 (pufa lc n-3) can make a nutritionally meaningful contribution to western diets in which consumption of pufa lc n-3 is low. enrichment of poultry meat with this fatty acid is usually achieved by inclusion of fish oil in broiler diet (23, 24). however, meat enriched in this way is susceptible to quality deterioration by lipid oxidation during storage or cooking, leading to reduction in nutritive value and accumulation of lipid oxidation products (10). oxidation is a very general process affecting lipids, pigments, proteins, dna, carbohydrates, and vitamins (11). the objective of this study was to evaluate the effects of dietary α-tocopherol (α-toc), pomegranate peel extract (ppe) and pomegranate peel (pp) on fatty acid profile, aoxidation and phenolic compounds in raw thigh and breast meat during refrigeration. materials and methods peels of pomegranate were harvested in october 2011 from pomegranate trees (ardestani, variety) in khorasan razavi province (east, iran). dried powders of peels (2.5 g) were extracted with 40 ml of methanol solvent at room temperature for 6 hours. three hundred and eighty four 1-d-old male broiler chicks (ross 308) were randomly allotted to 8 groups with 4 replicates of 12 birds. eight dietary treatments including control diet without feed additives, control diet mixed with 200 mg/kg α-toc, control diet mixed with ppe (100, 200 and 300 mg/kg), and control diet mixed with pp (1, 2 and 3 g/kg). in all diets 2% fish oil were added to enhance the enrichment of unsaturated n-3 fatty acid in birds. one broiler chick was randomly selected from each pen of 42 d of age. the antioxidative potential and various meat quality characteristics were determined on 0, 7, and 11 days of refrigerated storage. total phenols content in the aqueous supernatant was estimated by the folin-ciocalteu method (33). 1, 1-diphenyl-2-picrylhydrazyl (dpph) radical scavenging activity was estimated according to blois’ (2). lipid oxidation in sample was determined as the tbars value by using the method described by ahn et al. (1). fatty acid profile of samples was determined by gas chromatography (7). data were subjected to anova using the glm procedures of sas (27). results and discussion the fa composition of the diets, particularly pufa lc n-3, was modified and increased by the inclusion of fish oil in diet. the concentration of saturated fatty acid in the thigh and breast meat was not influenced in broilers fed pp, ppe, and α-toc diets as compared to control group. the results indicated that the tissue of broilers have a limited capacity for alteration of their saturated fatty acids (7). monounsaturated fatty acid (mufa) content in thigh and breast was decreased in birds fed diet containing pp, ppe and α-toc compared to control group (p<0.05). the increase storage of pufa decreased the synthesis of mufa by inhibiting the activity of 9-desaturase complex which is the key enzyme needed to convert sfas to mufas and this is compatible with our results (25). concentration storage of linolenic acid, eicosapentaenoic acid, docosapentaenoic acid, and docosahexaenoic acid in the thigh and breast meat of broilers fed diet containing pp, ppe and α-toc were higher than that of the control birds. this can be due to the antioxidative effects of phenolics compound added in diets. diet-containing antioxidant may inhibit the oxidation of pufa (13). thigh and breast meat of the broilers fed α-toc and ppe diets had significantly higher total phenolic content when compared with control or pp diets. polyphenolic compounds in ppe are distributed, retained, and remained functional in muscle (28). nagendra prasad et al. (20) suggested that polyphenol content showed highest relations with total antioxidant capacity. the development of lipid oxidation in the thigh and breast meat from broilers was delayed by diets antioxidants (pp, ppe, and α-toc). the thigh and breast meat from the broilers fed ppe, α-toc and pp diets produced low mda in spite of the higher content of pufa lc n-3 in diets which deteriorates the quality of the meat. these results agree with the other studies which depicted that the oxidation lipid decreased in broilers fed on various pufa levels and α-toc acetate. this was inhibited due to the antioxidant activity of α-toc acetate (11). the large amount of phenolics contained in pp and ppe diets may cause its strong antioxidant ability, extend the shelf life, and improve the quality of meat products. the dpph radical scavenging activity of the thigh and breast meat from the broilers fed α-toc and 200 and 300 mg/kg ppe in diets were significantly higher than that of the control group during the entire storage period, whereas lower significant difference was found in broilers fed pp diet compared to control birds. phenolic compounds present in the natural plant oils react with lipid and hydroxyl radicals and convert them into stable products (13). conclusion the results of the present study demonstrate that breast and thigh meat in broiler may be successfully enriched with lc pufa n-3 by the addition of fish oil to the diet. long-chain fatty acid n-3 was higher in broilers fed α-toc and/or ppe at the rate of 200 or 300 mg/kg diets. the dpph radical scavenging activity, tbars, and total phenolic content in the thigh and breast muscle were improved significantly in the ppe and α-toc fed birds. in conclusion, supplementation of diets with 200 and 300 mg ppe / kg can improve the anti-oxidative potential and functional qualities of thigh and breast meat in broilers. the ppe was an effective antioxidant as α-tocopherol in enriching the broiler meat.