Effect of pH and ATP on lipid oxidation in unwashed and washed seabass mince (Lates calcarifer) mediated by hemoglobin

Hemoglobin-mediated lipid oxidation was studied by using washed and unwashed seabass mince with and without added hemoglobin. Three pH values of postmortem fish were examined (physiological pH (6.5), 6.2, and 7.0). The lag time prior to thiobarbituric acid reactive substance development in the unwashed mince without added hemoglobin decreased greatly as the pH was reduced (p<0.05). Addition of hemoglobin decreased the lag time especially at the pH 6.2. In addition, the level of deoxyhemoglobin was found sharply increase with pH reduction in the range of pH 7.0 to 5.0. This suggested a potential role for deoxyhemoglobin as a catalyst. ATP lowered hemoglobin oxygenation at all pHs studied. Washing effectively prevented lipid oxidation in the washed mince without added hemoglobin. However, by addition of hemoglobin significant development of TBARS at low pH values except at pH 7.0. The results proved that ATP and low pH values increased oxidative activity of seabass hemoglobin. This investigation suggests that deoxyhemoglobin was a potent pro-oxidant