Effect of pH on lipid oxidation using trout hemolysate as a catalyst: A possible role for deoxyhemoglobin

Hemoglobin-mediated lipid oxidation was studied by adding hemolysate to was hed cod muscle. Three pH values were examined (pH 7.6, 7.2, and 6.0). The l ag time prior to rancidity and thiobarbituric acid reactive substance devel opment decreased greatly as the pH was reduced (p < 0.01). Formation of met hemoglobin due to autoxidation of the heme pigment was found to occur more rapidly at reduced pH. Also, the level of deoxyhemoglobin was found to shar ply increase with pH reduction in the range of pH 7.6-6.0. This suggested a potential role for deoxyhemoglobin as a catalyst. ATP lowered hemoglobin o xygenation at pH 7.2. Peroxidation of linoleic acid by oxy/deoxyhemoglobin and methemoglobin was investigated at two levels of preformed lipid hydrope roxides. At a reduced level of preformed lipid hydroperoxides, oxy/deoxyhem oglobin stimulated peroxidation of linoleic acid, whereas methemoglobin did not. At the higher level of preformed lipid hydroperoxides, both oxy/deoxy hemoglobin and methemoglobin were active. This investigation suggests that reduced hemoglobins played an important role in lipid oxidation processes.