Influence of sodium chloride on antioxidant enzyme activity and lipid oxidation in frozen ground pork

Ground pork containing 0-2.0% NaCl was stored at -15 °C for 10 weeks. During storage both thiobarbituric acid reactive substances (TBARS) and lipid peroxides increased with increasing NaCl concentrations. The activity of catalase (CAT), glutathione peroxidase (GSH-Px) and Superoxide dismutase (SOD) decreased 8, 32 and 27%, respectively, after 10 weeks of storage. CAT and SOD activity decreased primarily during the first week while GSH-Px activity decreased for up to 4 weeks. To determine if NaCl influenced enzyme inactivation rates, the activity of the antioxidant enzymes from stored, salted (0.5-2.0%) ground pork were determined at equal ionic strengths. Under these conditions, NaCl was not observed to accelerate CAT, SOD and GSH-Px inactivation in ground muscle during storage. However, altering ionic strength (0.5-2.0% NaCl) in the enzymes assays decreased the activity of muscle-extracted CAT, SOD and GSH-Px suggesting that NaCl could alter the activity of these enzymes in salted pork. The ability of NaCl to reduce the activity of the antioxidant enzymes could be partially responsible for the lower oxidative stability of salted muscle foods.