The emulsion (3 g) was transferred into 20-mL serum bottles, which were then tightly capped with rubber stoppers and aluminum caps. Samples with added iron were covered with aluminum foil to exclude light. All samples in bottles were oxidized in an Labtech Co., Seoul, Korea) under 1700 lux light and maintained at 25 °C for 10 d until taken out for analyses. All samples were prepared in duplicate.