Inhibitory effects of peptide-bound polysaccharides on lipid oxidation in emulsions

The inhibitory effects of polysaccharides on lipid oxidation in emulsions were investigated. Methyl linoleate was emulsified by β-casein or surfactants to prepare emulsions, and the oxidation was induced by an azo-compound or FeSO4 addition. The initial oxidation was followed by measuring the oxygen consumption in the emulsions for 30 min, and the extent of the lipid oxidation over a long time (∼48 h) was evaluated by the determination of the unoxidized lipid by gas chromatography and the thiobarbituric acid test. Peptide-bound polysaccharides, such as gum arabic and soluble soybean polysaccharides (SSPS), showed an ability to inhibit lipid oxidation, whereas maltodextrin and pullulan exhibited no inhibitory effects. Especially, SSPS almost perfectly suppressed the lipid oxidation from the initial to the late stages, irrespective of the emulsifiers and oxidation-inducing reagents. The mechanism whereby the peptide-bound polysaccharides inhibited the lipid oxidation in the emulsions is considered in terms of the chemical composition and other properties of the polysaccharides.