Singlet oxygen and ascorbic acid effects on dimethyl disulfide and off-flavor in skim milk exposed to light

The light-induced off-flavor and dimethyl disulfide increased as fluorescent light exposure increased from 0, 2, 4, 6, to 8h (P < 0.05), Sensory evaluation and identified compounds suggest that dimethyl disulfide was mainly responsible for the light-induced off-flavor in skim milk. Dimethyl disulfide was formed by the singlet oxygen oxidation of methionine in milk. Gas chromatographic analysis and sensory evaluation showed that 200, 500, and 1000 ppm ascorbic acid, which is a singlet oxygen quencher, lowered the formation of dimethyl disulfide and off-flavor in skim milk(P < 0.05).