30A-3 |
Oxidative stability of oil-in-water emulsions as a function of iron and surfactant hydroperoxide concentrations |
C. D. NUCHI, D. J. McClements, and E. A. Decker. Department of Food Science, University of Massachusetts, Chenoweth Lab, Amherst, MA 01003 Lipid oxidation is important in determining the shelf life of lipid containing foods. The mechanism of lipid oxidation in bulk oils has been widely studied. However, lipids are commonly found as emulsions in processed foods. Transition metals are important prooxidants in emulsions due to their ability to decompose hydroperoxides into free radicals. Hydroperoxides are important in the oxidative stability of emulsions since they are found in many ingredients including surfactants. The objective of this work was to determine the role of surfactant hydroperoxides and iron on the oxidation of lipids in oil-in-water emulsions. Two model systems were used: micelles and emulsions. Tween 20 was exposed to UV light to increase its hydroperoxide concentration. Methyl linoleate was solubilized in Tween 20 micelles and the pH was adjusted to 7.0. Micelles and salmon oil-in-water emulsions were prepared using Tween 20 with initial hydroperoxide concentrations ranging from 3 to 16 mmole/g. Ferrous concentrations ranged from 0 to 50 mM. Oxidation was followed by measuring headspace aldehydes and lipid hydroperoxides. In the absence of iron there was no significant difference in the oxidation rate of micelles for the samples prepared with Tween 20 regardless of their hydroperoxide concentrations. When ³ 10 mM ferrous sulfate was added, hexanal generation was significantly greater in the micelles prepared with higher levels of Tween 20 hydroperoxides (almost three times higher after 8 hours). In the emulsion systems containing iron (³ 1mM) significant differences in oxidation rates were observed as a function of Tween 20 hydroperoxide concentration. After 72 hours of incubation, the propanal concentration was three times higher for the sample prepared with the Tween 20 containing 15.6 mmole/g of hydroperoxides. These results suggest that surfactant peroxides could decrease the oxidative stability of iron containing foods.
Session 30A, Food Chemistry: Lipids
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