Factors affecting the binding of trout HbI and HbIV to washed cod mince model system and their influence on lipid oxidation

Electrostatic interactions between haemoglobin (Hb) and muscle components of fish may be an initial step of Hb-mediated lipid oxidation. This mechanism was investigated by examining the interaction of anionic HbIV and cationic HbI with insoluble components of washed cod mince under different pH and salt conditions. Lipid oxidation was monitored in parallel using the thiobarbituric acid reactive substances (TBARS) test. Higher binding of HbI to washed cod mince occurred compared to HbIV, yet HbIV better promoted lipid oxidation. An increase in pH from 5.7 to 6.3 and further to 7.0 lowered both Hb-binding and TBARS development. Addition of NaCl decreased Hb-binding but still did not influence Hb-mediated lipid oxidation. Thus, Hb binding had no consistent effect on lipid oxidation of washed cod mince. Rapid haemin release from the anionic Hb appeared to be a primary facilitator of lipid oxidation, overshadowing the greater binding ability of the cationic Hb.