| Abstract
| - The reducing and chelating capacities and the affinity for the incorporation into the fish muscle ofgrape procyanidins, hydroxytyrosol, and propyl gallate were studied together with their antioxidantactivity in frozen horse mackerel (Trauchurus trauchurus) fillets. Fillets were supplemented withphenolic antioxidants by (a) spraying an aqueous phenolic solution, (b) glazing with an aqueousphenolic solution, and (c) a previous washing of fillets with water plus spraying an aqueous phenolicsolution. The effect of washing on the endogenous pro-oxidant/antioxidant balance of the fillets wasalso determined. All phenolic compounds were effective delaying lipid oxidation in the fish fillets. Theorder of antioxidant efficiency in spraying and glazing was propyl gallate > hydroxytyrosol >procyanidins, which was similar to the reducing power of these phenolics, but did not show anycorrelation with their chelating capacity and their affinity to the fish muscle. Washing the fillets withwater prior to spraying phenols increased synergistically the antioxidant activity of grape procyanidinsand changed the relative antioxidant efficiency to propyl gallate ≈ procyanidins > hydroxytyrosol.This synergism may be a result of a better distribution of the procyanidins onto the fillet surfacebecause of the residual water that remained on the fillets surface after washing. Keywords: Frozen fish fillets; oxidation; grape procyanidins; hydroxytyrosol; washing; glazing;synergism
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