Preservation of the endogenous antioxidant system of fish muscle by grape polyphenols during frozen storage

The capacity of a phenolic extract, OW, obtained from grape (Vitis vinifera) by-products, and of a purified fraction of procyanidins from OW, fraction IV, for preservation of endogenous antioxidants of fatty fish was investigated during frozen storage. They were used in muscle concentrations of 0.01% (w/w). Grape polyphenols were compared with propyl gallate, a synthetic antioxidant. The exogenous compounds were added to minced mackerel (Scomber scombrus) muscle and horse mackerel (Trauchurus trauchurus) fillets, before freezing at –10 °C. The results demonstrated that grape polyphenols and propyl gallate inhibit the depletion of endogenous -tocopherol, ubiquinone-10 and total glutathione. Grape polyphenols and propyl gallate showed similar efficiency for preservation of ubiquinone, in both minced and filleted muscle, and total glutathione, in minced muscle. Total glutathione in the fillets was better maintained by propyl gallate than grape polyphenols. The endogenous antioxidant more efficiently preserved by grape polyphenols and propyl gallate was -tocopherol. Its loss elapsed faster in the order control> OW>fraction IV>propyl gallate. The depletion of -tocopherol was highly correlated with the evolution of lipid oxidation. The development of lipid oxidation was repressed, while the concentration of -tocopherol was not reduced up to critical levels.