Prooxidative and antioxidative properties of β-carotene in chlorophyll and riboflavin photosensitized oil-in-water emulsions

초록

Effects of beta-carotene on the oxidative stability of chlorophyll or riboflavin photosensitized oil-in-water (O/W) emulsions were determined by analysing the depleted headspace oxygen content, lipid hydroperoxides, fluorescence intensity, and headspace volatiles. As the concentration of beta-carotene increased from 0 to 10, 100, and 1000 mu M, the oxidative stability of samples containing chlorophylls decreased in a concentration-dependent manner under light, indicating that beta-carotene acted as a prooxidant. However, in riboflavin photosensitized O/W emulsions, 100 and 1000 mu M beta-carotene inhibited lipid oxidation. Although beta-carotene protected both photosensitisers in O/W emulsions, beta-carotene displayed antioxidative or prooxidative properties, which depended on the polarity of the photosensitisers. The development of t-2-heptenal and 1-octen-3-ol increased greatly in chlorophyll sensitised O/W emulsions with an increase in beta-carotene concentration, implying that more singlet oxygen oxidation occurred due to the higher levels of remaining chlorophylls. However, the content of t-2-heptenal and 1-octen-3-ol in the riboflavin sensitised O/W emulsions was not significantly correlated with the beta-carotene concentration, which indicates that beta-carotene in the lipid particles effectively quenched singlet oxygen. (C) 2013 Elsevier Ltd. All rights reserved.

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