COMPARATIVE-STUDY ON THE OXIDATIVE STABILITY OF PHOSPHATIDYLCHOLINES FROM SALMON EGG AND SOYBEAN IN AN AQUEOUS-SOLUTION

The oxidative stability of phosphatidylcholine from salmon egg (salmon egg PC) was higher than that of soybean PC in an aqueous solution (pH = 7.4 at 37 degrees C) with Fe2+-ascorbic acid as a catalyst, although the average numbers of bisallylic positions in the salmon egg PC molecule and in the soybean PC molecule were 4.28 and 1.59, respectively. This high average with salmon egg PC was due to its high contents of docosahexaenoic acid (22:6n-3, 24.3 mol%) and eicosapentaenoic acid (20:5n-3, 14.2 mol%), while the major polyunsaturated fatty acid in soybean PC was linoleic acid (18:2n-6, 67.6 mol%). The oxidative stability of both PCs was strongly influenced by an emulsifier. PC was oxidatively most stable when it was dispersed with chicken egg albumin, followed by Tween 20 and deoxycholic acid sodium salt. These data suggest that the oxidative stability of polyunsaturated PC in an aqueous solution is mainly correlated with the conformation of the PC molecule and the phase behavior of PC aggregation.