Effect of Sunlight on Mixtures of Vegetable Oils and Pigments

Abstract

SUNLIGHT, according to recent work in these laboratories, is much more active in producing peroxides in the extracted crude lipids of certain vegetables (Lee, F. A., unpublished data), than in ordinary oils¹. It is known that peroxides are produced when chlorophyll dissolved in oils or in oleic acid is exposed to light^2,3 and that, in the presence of chlorophyll, certain oils autoxidize⁴. Since the crude lipid preparations from green vegetables contain carotenes as well as chlorophyll, the effect of sunlight on colourless or nearly colourless oils mixed either with carotene or with carotene and chlorophyll was investigated. Chevallier et al. ⁵ studied the changes taking place in mixtures of triolein and carotene. They found that β-carotene retards the oxidation of triolein in the dark, but accelerates it in the light of a mercury-vapour lamp. In addition, chlorophyll dissolved in triolein prevents the oxidation-accelerating action of β-carotene in the presence of mercury-vapour light. In that work the chlorophyll and the β-carotene solutions were separated by glass. The chlorophyll solution completely absorbed the violet and blue rays emitted by the lamp.