Chelators impact pro-oxidant activity of iron in oil-in-water emulsions.

Pro-oxidants, such as iron, are naturally present in food emulsions at levels high enough to promote lipid oxidation. Many oil-in-water emulsions contain chelators that can alter lipid oxidation rates. One way that chelators--small molecules that bind very tightly to metal ions--can impact lipid oxidation is through their ability to alter the physical location of iron.

University of Massachusetts scientists evaluated the ability of chelators to influence the physical location and pro-oxidant activity of iron in oil-in-water emulsions. Ferric ions were dissolved in corn oil. Iron-containing lipids (20%) were then emulsified with 64 mM polyoxyethylene-10-lauryl ether using a sonication technique. The researchers then added sodium tripolyphosphate (STPP), ethylene diaminetetraacetic acid (EDTA), citric acid and whey protein isolate (WPI) to the emulsion.

Emulsion droplets and continuous phases were separated using centrifugation. The scientists quantified ferric ions in the continuous phase spectrophotometrically. They used lipid hydroperoxides and headspace hexanal to follow the lipid oxidation process.

The continuous phase ferric ion concentration in the emulsions increased with increasing chelator concentrations and storage time, up to seven days. At pH 3.0, the continuous phase concentration of ferric ions was higher than at pH 7.0 in the presence of chelators. The formation of lipid hydroperoxides and headspace hexanal in corn oil-in-water emulsions containing ferric ions decreased with growing chelator concentrations.

These results indicate that chelators can alter the physical location and pro-oxidant activity of iron in oil-in-water emulsions. Understanding how chelators impact the pro-oxidant activity of iron could lead to the development of new antioxidant technologies.

Further information. D. Julian McClements, Department of Food Science, University of Massachusetts-Amherst, Chenoweth Laboratory, Box 31410, Amherst, MA 01003; phone: [phone]; email: [e-mail].