Oxidative stability of sardine and mackerel lipids with reference to synergism between phospholipids and α‐tocopherol

Relationships between oxidative stability and the compositions of sardine and mackerel lipids were investigated in view of possible synergism between phospholipids and α ‐tocopherol ( α ‐Toc). The total lipids extracted from viscera were highly susceptible to autoxidation, compared with lipids of white and red muscles and of skin. This seemed to be due to lower concentrations of α ‐Toc and phosphatidylethanolamine (PE) in the tissue, but not to the level of polyunsaturated fatty acids. The synergistic effect of PE with α ‐Toc seemed to be slightly affected by the degree of unsaturation of its fatty acyl chains. The synergistic ability of O ‐phosphoethanolamine, the base moiety of PE, was higher than that of O ‐phosphoserine. O ‐Phosphocholine was only slightly effective. During the induction period of autoxidation, the α ‐Toc level decreased rapidly, and rapid lipid oxidation began only after α ‐Toc was almost exhausted.