Effect of randomization on the oxidative stability of corn oil

Abstract

Randomized corn oil TAG oxidized much faster than natural oil, but after purification with alumina, they oxidized at the same rate. We showed that this effect could not be attributed to a difference in total tocopherols in the randomized and natural oils. Polar material recovered from the alumina treatment was fractionated by TLC, and a pro-oxidant effect was found in the fractions containing MAG and DAG. However, MAG and DAG, although mild pro-oxidants, could not account for the prooxidant effect generated by randomization. No other compounds could be detected in the MAG fraction by MS. The pro-oxidant effect of randomized oil disappeared when EDTA or citric acid was added in sufficient amounts. The pro-oxidant effect of randomized corn oil was increased by the incorporation of additional copper or iron at a concentration that did not catalyze oxidation of the purified oil. Treatment of corn oil with ascorbic acid, ascorbyl-6-palmitate, ethyl acetoacetate, ethyl diacetoacetate, and acetylacetone did not reproduce the effect of the unknown pro-oxidant. Although the identity of the pro-oxidant is still unknown, we have confirmed that it is produced during randomization; it does not have pro-oxidant activity alone, but it facilitates the catalytic activity of the transition metal ions.

The Role of Plasmalogen in the Oxidative Stability of Neutral Lipids and Phospholipids

“…Therefore, the soybean oil after removal of tocopherols is a good model for studying antioxidant effects because of its richness in double bonds. Our previous test with the same procedure showed that at least 99% of the naturally occurring tocopherols were removed by purification with activated alumina (28).…”

Influence of sn‐1,3‐lipase‐catalysed interesterification on the oxidative stability of soybean oil‐based structured lipids

“…Mistry and Min 21 reported that MAG and DAG acted as pro-oxidants at concentrations of 0.25-0.5% at 55 • C in purified soybean oil. Wang et al 17 reported that polar material recovered from randomised corn oil by using an alumina column after TLC fractionation had a pro-oxidant effect. Therefore, we purified SLs and SBO using a silica column.…”

“…It was found that the addition of a small amount of metal ions significantly decreased the oxidative stability index (OSI) of randomised corn oil. 17 Akoh and Moussata 16 reported that SL which was produced by enzymatic interesterification of canola oil or fish oil and CA was less stable than the unmodified canola or fish oil. In contrast, Kimoto et al 18 determined that enzymatic interesterification with random lipase caused an increase of oxidative stability of fish oil because the level of highly unsaturated TAGs was decreased.…”

Oxidative Stability of Egg and Soy Lecithin as Affected by Transition Metal Ions and pH in Emulsion

“…Lecithin, 5 g, was first subjected to saponification by following AOCS official method Ca 6a-40 (10), and the unsaponifiable matter was extracted. The extract was used for HPLC quantification for tocopherols.…”