Role of iron and hydroperoxides in the degradation of lycopene in oil-in-water emulsions.

Lycopene has recently received interest as an antioxidant in human tissues. These antioxidant properties, however, present challenges to preventing oxidative degradation of lycopene within food products. In this research, oxidation of lycopene in a model emulsion system was examined. Lycopene loss was monitored using a spectrophotometer with an integrating sphere. Light was found to have little influence on the degradation of lycopene at pH 3, 5, or 7. The pH of the emulsion had a significant impact on the stability of lycopene, with most rapid degradation occurring in emulsions at pH 4 and below. Addition of EDTA significantly increased the stability of lycopene. Addition of TBHQ showed little impact on lycopene stability at pH 3, but exhibited a greater effect at pH 7. These results suggest that transition metal induced oxidation of lycopene may be the predominant mechanism of degradation at low pHs. At higher pHs, attack by free radicals was found to be a contributing mechanism to lycopene oxidation.