Effects of Dietary Red Grape Extract on the Quality Traits in Juvenile European Sea Bass (Dicentrarchus labrax L.)

SIMPLE SUMMARY: The need to satisfy the growing demand of aquaculture production has led to an increase of intensive fish farming techniques that are held responsible for the occurrence of various stressors that affect the health of cultured animals. Polyphenols are plant-derived compounds with known biological activities and positive influences on the performances and immunity of fish. The aim of the present study was to evaluate the effects of dietary inclusion of a polyphenol extract obtained from Nero di Troia red grape, tested at two concentrations, on the quality of juvenile farmed sea bass (Dicentrarchus labrax) fillets. The two diets containing polyphenol extracts overall improved the fish quality features; in particular, dietary inclusion of grape extracts lowered the concentration of total fat and saturated fatty acids along with the Atherogenic index, with benefits for human health. No differences arose between the two GPE concentrations tested; therefore, the polyphenol-rich extract showed its antioxidant effectiveness in preventing lipid oxidation and enhancing fish fillet quality already at the lower concentration. Further investigation is needed in order to study the effects of the experimental diets on fish performances, immune status, and flesh quality upon achievement of the sea bass market size. ABSTRACT: Intensive fish farming is responsible for the occurrence of various stressors that negatively affect the health of cultured animals. Polyphenols are plant-derived compounds with biological activities and positive influences on the performances and immunity of fish. The aim of the present study was to evaluate the effects of dietary inclusion of a polyphenol extract obtained from Nero di Troia red grape on the quality of farmed sea bass (Dicentrarchus labrax) fillets. Three diets were tested: control (n = 90) received a conventional feed, whereas the two experimental groups (n = 90 each) received the control feed supplemented with the red grape polyphenol extract (GPE) at the concentration of 100 (GPE 100) or 200 mg/kg (GPE 200). The two GPE diets lowered (p < 0.05) the red (a *) and yellow (b *) indexes, fillet hardness, and total lipid content. Chewiness, concentration of saturated fatty acids, and the Atherogenic Index were higher (p < 0.05) in the control group; GPE diets increased (p < 0.05) the polyunsaturated fatty acids content. Furthermore, the concentration of malondialdehyde was lower (p < 0.05) in fillets of the GPE groups, thus confirming the antioxidant effect of the red grape extract and its effectiveness in preventing lipid oxidation.