OXIDATIVE STABILITY OF FREE FATTY-ACID MIXTURES FROM SOYBEAN, LINSEED, AND SARDINE OILS IN AN AQUEOUS-SOLUTION

The oxidative stability of free fatty acid (FFA) mixtures from soybean, linseed, and sardine oils in an aqueous solution was compared with that in air. Due to its high contents of DHA and EPA, sardine oil FFA was most rapidly oxidized in air, followed by linseed and soybean oil FFAs. However, this order was reversed in autoxidation in an aqueous solution (pH=7.4 at 37-degrees-C). Gas chromatographic analysis showed that sardine oil FFA was most oxidatively stable in the aqueous solution and about 78% of polyunsaturated fatty acids (PUFAs) remained unchanged after 168 h of oxidation, while soybean oil FFA was highly susceptible to autoxidation in the aqueous solution, losing more than 80% of PUFAs after only 40 h of oxidation. This unusual order of oxidative stability in an aqueous solution can be explained by correlation with the micellar conformations of individual FFA mixtures in an aqueous solution.