Impact of lipid composition and muscle microstructure on myoglobin-mediated lipid oxidation in washed cod and pig muscle.

• Understanding of the endogenous factors which effect lipid oxidation are needed. • Myoglobin promoted lipid oxidation in WCM but not WPM. • Two phospholipids (polyenoic indexes: 282, 24) showed similar oxidation rate in WPM. • Muscle microstructure plays critical roles in Mb-mediated lipid oxidation. • Accessibility of phospholipids to Mb was more important than its unsaturation. The roles of lipid oxidation substrates and muscle microstructure in lipid oxidation were investigated in two muscle models (cod and pig). Added myoglobin (Mb) promoted lipid oxidation in washed cod muscle (WCM) but not in washed pig muscle (WPM). The differing microstructure of WCM e.g. more exposed fat cells or membrane of muscle cells compared to the "denseness" or "wrapped" structure of WPM, may have contributed to the better ability of Mb to facilitate lipid oxidation in the WCM. Added phospholipids with polyenoic indexes of 282 and 24 activated Mb as an oxidant similarly in WPM while added neutral lipids and added free fatty acids had little effect. It is suggested that muscle microstructure and accessibility of Mb to phospholipids play critical roles in relation to Mb-mediated lipid oxidation while the degree of unsaturation in the phospholipids was less important. [ABSTRACT FROM AUTHOR]