Improving the stability of wheat protein-stabilized emulsions: Effect of pectin and xanthan gum addition

The potential of two anionic polysaccharides, pectin and xanthan gum, to improve the physical stability of emulsions containing lipid droplets coated by wheat protein (deamidated gliadin) was investigated. Polysaccharide type and solution pH had a major impact on biopolymer interactions in solution: wheat protein interacted with xanthan gum from pH 3.5 to 7, but with pectin from pH 3.5 to 5, which was attributed to different polysaccharide charge densities. Biopolymer interactions in solutions were related to their adsorption behavior in emulsions. Wheat protein-stabilized emulsions were highly unstable to aggregation at pH values around their isoelectric point (pI ≈ 5) and at elevated NaCl (≥100 mM, pH 7) or CaCl2 (≥10 mM, pH 7) levels. Adding xanthan gum improved emulsion stability to high ionic strengths, with no phase separation observed during storage for 4 weeks. Adding pectin improved emulsion stability at acidic pH, but the emulsions were still unstable at elevated ionic strengths. These results are useful for the increased utilization of wheat proteins as functional ingredients in the food industry.