Effect of myoglobin from Eastern little tuna muscle on lipid oxidation of washed Asian seabass mince at different pH conditions.

The effect of pH (6.0, 6.5, and 7.0) on lipid oxidation in washed Asian seabass (Lates calcarifer) mince mediated by oxymyoglobin from the dark muscle of little Eastern tuna (Euthynnus affinis) during 8 d of refrigerated storage was studied. Metmyoglobin formation and discoloration increased with increasing storage time and the changes were more pronounced at lower pH. The highest lipid oxidation and off-odor development were observed when myoglobin was incorporated in washed mince at pH 6.0. At low pH, oxidation of myoglobin took place and lipid oxidation in washed mince was enhanced. This was concomitant with the increased fishy and rancid off odor in the sample containing myoglobin, especially at pH 6.0. Washed mince containing myoglobin at pH 6.0 had 1-octen-3-ol and hexanal as the major volatile compounds. Thus, postmortem pH and myoglobin played an essential role in lipid oxidation and off odor in fish muscle during the extended storage. Myoglobin plays a role in the color of fish muscle. The change of myoglobin affects not only consumer acceptability, but also lipid oxidation as well as odor. The control of pH of muscle could be a potential means to lower the lipid oxidation mediated by myoglobin. As a consequence, the prime quality of fish with a negligible fishy odor could be maintained during postharvest handling or storage.