Orientador: Prof. Dr. Ricardo Pereira Ribeiro 

 Data da Defesa: 19/10/2015



INTRODUCTION. Tilapia (Oreochromis niloticus) is the second most farmed fish group worldwide and over the past decade has quadrupled in production. Tilapias possess the ability to desaturate and chain elongate linoleic acid (18:2n-6, LA) to arachidonic acid (20:4n-6, AA) and linolenic acid (18:3n-3, LNA) to eicosapentaenoic acid (20:5n3, EPA) and docosahexaenoic acid (22:6n-3, DHA). The consumption of n-3 PUFA such as EPA and DHA plays an important role in human nutrition, disease prevention, and health promotion. Diet is a well-established factor that determines the fatty acid composition in meat, especially affecting the n‐6/n‐3 ratios in freshwater fish. Several studies have demonstrated the increase n-3 PUFA in tilapia through dietary supplementation with vegetable sources rich in omega-3. Perilla (Perilla frutescens) a traditional oilseed from Asian countries, is an excellent source of alpha-linolenic fatty acid (LNA), containing approximately 60% of total fatty acid. The use of antioxidants in animal diets is recommended to decrease oxidative processes and preserve the quality of meat and meat products, especially those enriched with n-3 PUFA. Due to the potential toxic effects of synthetic antioxidants, natural antioxidant sources especially fruits are being preferred now-a-days for use in different meat products. Several study has demonstrated the possibility of recovering high amounts of polyphenols from agroindustrial co-products, who could be explored as source of natural antioxidants. AIMS. The objective of this study was to evaluate the effect of dietary supplementation with strawberry co-product extract (SCE) rich in polyphenols or vitamin E (VE) on lipid profile and nutritional quality of tilapia GIFT fillets enriched with n-3 fatty acid. Moreover, to investigate the influence of supplementation on antioxidant capacity and lipid oxidation. MATERIALS AND METHODS. Two hundred twenty-five Nile tilapia (Oreochromis niloticus) of the GIFT (Genetic Improvement of Farmed Tilapia) strain were cultivated for a period of 60 days. The fish were fed with five experimental diets: a basal diet without antioxidant (CON, control), and four diets which were supplemented with different antioxidants (150 mg kg-1): butylated hydroxytoluene (BHT; synthetic antioxidant), strawberry co-product extract (SCE; natural antioxidant), vitamin E (VE, α-tocopherol) and blend of SCE+VE (1:1). All experimental diets were rich in omega-3 fatty acids, with addition 4% perilla oil as lipid source. Analysis of fatty acid (FA) composition by GC–FID and triacylglycerol (TAG) composition by ESI (+)-MS were used to evaluate the lipid profile of tilapia fillets from different treatments. Based on the FA data, were calculated nutritional quality indices of lipids. Analysis of total phenolic compounds (TPC) and antioxidant capacity, for different assays (ABTS, DPPH and ORACFL) were measured in fractions of hydrophilic and lipophilic of tilapia fillets at 0, 30 and 60 days of experiment. The lipid oxidation (TBARS index) was determined at 0, 30, 60 and 90 days during frozen storage (-18 °C). RESULTS AND DISCUSSION. After 60 days of experiment, was observed a decrease in the concentration of SFA and MUFA, and a significant increase of PUFA in tilapia GIFT fillets. As a result, there was an increase of n-3 fatty acids. SCE showed the highest concentration for n-3, which represented an increase of approximately 457% 13 compared to the initial sample, and treatments could be ranked in the following sequence: SCE>SCE+VE>BHT>CON>VE. Concerning to nutritional quality indices of lipids, there was a decrease the ratio n-6/n-3, AI and TI. SCE and SCE+VE presented the smallest values. Results of TAG analysis exhibited a concordance with FA composition, which demonstrated that fillets from SCE and SCE+VE diets presented higher concentrations of n-3 fatty acids. TPC in tilapia fillets was increased, which SCE showed the highest result. Both treatments supplemented with strawberry co-product extract, SCE and SCE+VE presented highest antioxidant capacity of all employees assays. In general, the hydrophilic fraction of tilapia fillets demonstrated superior results than the lipophilic fraction for all treatments, which can be confirmed by the good correlation of the TAC between H-ORACFL (r = 0.9827) and TPC (r = 0.8423) . The PCA analysis separated the treatments and distinguished SCE and SCE+VE, confirming the high antioxidant capacity of the treatments with the addition of strawberry co-product extract. Low lipid oxidation value. CONCLUSIONS. Therefore, strawberry co-product extract demonstrated a positive effect in the incorporation of fatty acids n-3, could be used as a natural antioxidant in the diet of animals, improving the quality of lipid profile in muscle tissue. Furthermore, supplementation of antioxidants in the diet promoted a protective effect against lipid oxidation during storage. Therefore, strawberry co-product extract proved to be a promising natural antioxidant to improve antioxidant capacity and quality of fish fillet, to be used in animal diets.

 Key-words: alpha-linolenic; omega-3 fatty acid; lipid profile; Perilla frutescens; natural antioxidant, co-product; antioxidant capacity; lipid oxidation. 




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