Influence of anionic polysaccharides on the physical and oxidative stability of hydrolyzed rice glutelin emulsions: Impact of polysaccharide type and pH

Abstract

The objective of this study was to investigate the effect of anionic polysaccharide addition on the physical and oxidative stabilities of fish oil-in-water emulsions coated by hydrolyzed rice glutelin (HRG) under conditions where the droplets and polysaccharides had similar (pH 7) or opposite (pH 3.5) charges. At pH 7, the addition of xanthan gum (XG) promoted droplet aggregation and creaming in the emulsions, which was attributed to a depletion mechanism; while the addition of pectin had little impact on their physical stability. At pH 3.5, the aggregation and creaming stability of the emulsions was greatly enhanced by addition of either anionic polysaccharide, with XG being more effective than pectin. The oxidative stability of all the emulsions was higher at pH 7 than at pH 3.5 due to the higher water-solubility of iron under acidic conditions. The oxidative stability of the emulsions was improved by pectin addition at both pH values, and by XG addition at pH 3.5. However, their oxidative stability was decreased by XG addition at pH 7. These results were attributed to differences in the ability of the two polysaccharides to bind pro-oxidant iron ions, as well as on their impact on droplet aggregation. This study provides information that will be valuable for the rational design of food emulsions fortified with polyunsaturated ω-3 long chain polyunsaturated fatty acids (PUFAs).