The role of tocopherol on photooxidation reactions palm oil emulsion in water

Abstract

Lipid oxidation is one of the main deteriorative reactions that takes place during preparation and storage of many food products. This can make it unacceptable for human consumption.. In food emulsion, oxidation reaction can be occurred by either diradical triplet oxygen or nonradical singlet oxygen. The singlet oxygen can be formed from triplet oxygen by photooxidation. The purpose of this research was to study the effect of singlet oxygen quencher such as tocopherol on lipid oxidation rate in the erythrosine-sensitized photooxidation of oil-in-water emulsion. Palm oil-in-water emulsion, containing erythrosine 100 ppm and tocopherol 0, 25, 50, 75 and 100 ppm, were prepared with polyoxyethylene sorbitan monolaurate (Tween 20). The mixtures were stored under 4,000 lux fluorescent light for 10 h and peroxide values were measured at 2 h interval. Erythrosine greatly increased the photooxidation of palm oil-in-water emulsion, as expected. Lipid oxidation rates, as determined by the formation of lipid hydroperoxides in palm oil-in-water emulsions containing erythrosine decreased with increasing tocopherol concentration. At pH 3, the peroxide value was higher than at pH 7, ie., from 8,03 to 6.08 respectively. The results indicate that tocopherol is an effectively singlet oxygen quencher in palm oil-in-water emulsion.