14B-25

C. D. NUCHI¹, J. R. Mancuso², D. J. McClements¹, and E. A. Decker¹. (1) Department of Food Science, University of Massachusetts, Chenoweth Lab, Amherst, MA 01003, (2) General Mills, Minneapolis, MN

Lipid oxidation is an important factor that determines the shelf life of food emulsions. Tween 20, a commonly used food surfactant, usually contains preexisting peroxides, which could potentially be decomposed thus promoting lipid oxidation by forming free radicals.

The objective of this research was to determine how the peroxide content of surfactants could impact the oxidative stability of food emulsions.

Salmon oil (5%) and Tween 20 (17 mM) in an acetate - imidazole buffer (5 mM each) were mixed and then sonicated for 2 min to make the emulsion. Surfactant was used as purchased or was exposed to UV light to increase peroxide concentrations. The oxidation was monitored by measuring lipid peroxides and headspace aldehydes.

Surfactants such as Tween 20 contain peroxides with concentrations ranging from 0.2 to 34.9 umol/g Tween 20. Iron accelerates the decomposition of Tween 20 peroxides with decomposition being greater at pH 3.0 than 7.0. In micelle systems, the iron promoted decomposition of Tween 20 peroxides resulted in the oxidation of a-tocopherol with 100% and 27% oxidation occurring after 0.5 hr at pH 3.0 and 7.0, respectively. Tween 20 peroxides also accelerated the oxidation of methyl linoleate in micelle systems with headspace hexanal concentrations increasing 6-fold after 6 hr. Salmon oil-in-water emulsions prepared with Tween 20 that is low (3.2 umol/g) or high (14.4 umol/g) in peroxides had similar oxidation rates as determined by lipid peroxides and headspace propanal.

Decomposition of peroxides originating from Tween 20 can result in the oxidation of lipids. In micelle systems, Tween 20 peroxide decomposition will accelerate the oxidation of both a-tocopherol and methyl linoleate. However, in lipid emulsions increasing Tween 20 peroxide concentrations over 4-fold had little influence on oxidation rates suggesting that surfactant peroxides may not have a great impact on oxidative stability.