The objective of this research was to evaluate the ability of O/W microemulsion containing astaxanthin and α-Tocopherol to inhibit the formation of dimethyl disulfide in an aqueous model system containing methionine, skim milk, and full cream milk due to riboflavin photosensitization. In addition, the formation of hexanal and the presence of sunlight flavor were also determined in skim milk and full cream milk. Astaxanthin 200 ppm and α-Tocopherol 1000 ppm were incorporated into the O/W microemulsion. Two percent of O/W microemulsion containing astaxanthin and α-Tocopherol was added to the samples and exposed to fluorescence light at 2000 Lux in the showcase at 100C for up to 8 h. The O/W microemulsion containing astaxanthin and α-Tocopherol effectively inhibited the formation of dimethyl disulfide in an aqueous model system containing methionine, skim milk and full cream milk. Hexanal formation was inhibited in skim milk and full cream milk. The presence of sunlight flavor in skim milk and full cream milk could be detected by panelists after 2 and 4 h of fluorescent light exposure, respectively. However, the sunlight flavor was not detected when O/W microemulsion containing astaxanthin and α-Tocopherol was added to the skim milk and full cream milk.