Oxidative and flavor stability of oil from lipoxygenase-free soybeans

Soybeans that lack or contain three lipoxygenase (LOX) isozymes, LOX-1, LOX-2, and LOX-3, were evaluated for oxidative and flavor stability at 60 degrees C in the dark and at 35 degrees C in the light. Although the two types of soybeans had a similar genetic background, there were significant differences (P less than or equal to 0.01) in fatty acid percentages between the lipoxygenase-free and normal oils before and after storage at both temperatures. The linolenic acid content of oil from LOX-free germplasm before storage averaged 7.2%, while normal lines averaged 6.6%. The linoleic acid content after storage averaged 6.9% for LOX-free and 6.6% for normal oils. LOX-free oil was not significantly different from normal oil in flavor, as judged by a sensory panel, or in concentrations of volatiles during storage at either storage condition. LOX-free oil had less hexanal than normal oil before storage, but had significantly greater(P less than or equal to 0.05) levels after storage for two weeks at 35 degrees C. Peroxide values of oil from LOX-free soybeans were significantly greater(P less than or equal to 0.01) than oil from the normal soybean after storage at 60 and 35 degrees C. LOX-free oil had significantly greater (P less than or equal to 0.01) levels of alpha-, beta-, and gamma-tocopherols. In general, oil from LOX-free soybeans did not have improved flavor or oxidative stability. Differences between the two oil types in peroxide value and in production of a few volatiles were probably a result of the differences in initial fatty acid composition.