Impact of Surface Active Compounds on Iron Catalyzed Oxidation of Methyl Linolenate in AOT–Water–Hexadecane Systems

Abstract

Edible oils contain minor surface active components that form micro-heterogeneous environments, such as reverse micelles, which can alter the rate and direction of chemical reactions. However, little is known about the role of these micro-heterogeneous environments on lipid oxidation of bulk oil. Our objective was to evaluate the ability of water, cumene hydroperoxide, oleic acid, and phosphatidylcholine to influence the structure of reverse micelles in a model oil system: sodium bis(2-ethylhexyl) sulfosuccinate (aerosol-OT; AOT) in n-hexadecane. The influence of reverse micelle structure on iron catalyzed lipid oxidation was determined using methyl linolenate as an oxidizable substrate. The size and shape of the reverse micelle were investigated by small-angle x-ray scattering, and water contents was determined by Karl Fischer titrations. Lipid hydroperoxides and thiobarbituric acid reactive substances were used to follow lipid oxidation. Our results showed that AOT formed spherical reverse micelles in hexadecane. The size of the reverse micelles increased with increased water or phosphatidylcholine concentration, but decreased upon addition of cumene hydroperoxide or oleic acid. Iron catalyzed oxidation of methyl linolenate in the reverse micelle system decreased with increasing water concentration. Addition of phosphatidylcholine into the reverse micelle systems decreased methyl linolenate oxidation compared to control and reverse micelles with added oleic acid. These results indicate that water, cumene hydroperoxide, oleic acid, and phosphatidylcholine can alter reverse micelle size and lipid oxidation rates. Understanding how these compounds influence reverse micelle structure and lipid oxidation rates could provide information on how to modify bulk oil systems to increase oxidative stability.

Influence of iron solubility and charged surface-active compounds on lipid oxidation in fatty acid ethyl esters containing association colloids

“…Chayasit reported similar results of this study in that iron (II) sulfate increased the oxidation rate of methyl linoleate in the sodium bis(2-ethylhexyl)sulphosuccinate (AOT) reverse micelle system, but did not change the oxidation rates without AOT reverse micelles (Chayasit et al, 2007). Both iron (II) sulfate and iron (III) sulfate are water-soluble and could partitioned into the water core of association colloids as iron (II) and iron (III) ions.…”

“…Iron is one of the most important prooxidative transition metals found in oils due to its high concentration. Water-soluble iron compounds, such as iron (II) sulfate and iron (II) chloride, were reported to be prooxidative in oils with association colloids (Chayasit, Stanley, Strey, McClements, & Decker, 2007;Chen, Panya, McClements, & Decker, 2012). However, the effect of oil-soluble and oil/water insoluble iron compounds has not been investigated.…”

Phospholipids in foods: prooxidants or antioxidants?

“…The ability of hydroperoxides to reduce interfacial tension and thus be amphiphilic was also confirmed by Nuchi et al Trunova et al reported that both cationic reverse micelles formed by cetyltrimethylammonium bromide (CTAB) and anionic reverse micelles formed by sodium dodecyl sulfate (SDS) increased the decomposition of ethylbenzene and limonene hydroperoxides . In another reverse micelle system that used AOT as surfactant (AOT/water/hexadecane), the authors found that lipid oxidation rates of methyl linolenate were altered upon the addition of cumene hydroperoxides, water, oleic acid or PC …”

“…70 In another reverse micelle system that used AOT as surfactant (AOT/water/hexadecane), the authors found that lipid oxidation rates of methyl linolenate were altered upon the addition of cumene hydroperoxides, water, oleic acid or PC. 77 The presence of phospholipid reverse micelles in bulk oils creates oil-water interfaces where hydrophilic (e.g. iron) and amphiphilic (e.g.…”

Effects of Deuterium Oxide on the Oxidative Stability and Change of Headspace Volatiles of Corn Oil

“…Major factors for lipid oxidation are the degree of unsaturation in lipids and the presence of oxygen molecules such as triplet or singlet oxygen. Also, minor components in oils including transition metals, moisture, phospholipids (PL), sterols, and the presence of antioxidants greatly influence oxidative stability [1][2][3][4].…”