Effects of paprika pigments on oxidation of linoleic acid stored in the dark or exposed to light

We examined the antioxidant effects of paprika pigments on oxidation of linoleic acid and on decoloration of the sample when stored at 37 degrees C in the dark or exposed to fluorescent light for 8 h per day. (1)H nuclear magnetic resonance with dioxane as an external proton reference was used to estimate the oxidative deterioration of linoleic acid. Oxidation was estimated by observing the ratio of the divinylmethylene proton signal area in linoleic acid vs the proton signal area in dioxane. The addition of paprika pigments suppressed the oxidation of linoleic acid during storage in the dark, and the effect was markedly increased with increasing concentrations (0.02, 0.2, and 2%). When the linoleic acid with added paprika pigments was exposed to light, only a slight suppression of oxidation was observed, and the color of the sample disappeared more rapidly than that in the dark. At the time of decoloration of the sample with added pigments, considerable oxidation of linoleic acid occurred. As the color change is due to degradation of the pigment, an increase in oxidation at the time of discoloration is consistent with the pigments functioning as antioxidants. The addition of alpha-tocopherol to paprika pigments stabilized degradation of the pigments by light. Although the addition of alpha-tocopherol to linoleic acid with added paprika pigments prolonged the decoloration of the sample under light, the prevention of oxidation under the light condition was not as effective as for the samples stored in the dark.