Effects of antioxidants on copper induced lipid oxidation during salting of cod (Gadus morhua L.)

A model system for studying lipid oxidation of salted cod muscle was used for investigating the interaction effects of antioxidants and copper in the brine. The results showed that ascorbate might have pro-oxidative or antioxidative effects depending on the ascorbate and metal concentrations. Without added copper in the brine, concentrations of < 500 ppm ascorbate had a pro-oxidative effect. With 5 ppm copper added in the brine, low concentrations of ascorbate (< 50 ppm) inhibited the formation of TBARS (thiobarbituric acid - reactive substances) in the cured product. At slightly higher concentrations (100-200 ppm), the antioxidative properties were lost. Above 200 ppm the added ascorbate reduced the oxidation level in the salt-ripened product. The application of ascorbate as an antioxidant in salt curing of cod requires the use of high concentrations (> 1,000 ppm) in the brine. When similar concentrations (0.5 mM) of EDTA (ethylenediaminetetraacetic acid), citrate or ascorbate were included with 3 ppm copper in the brine, EDTA was the only compound that efficiently inhibited copper-induced lipid oxidation.