Stability of pH-responsive Pickering emulsion stabilized by carboxymethyl starch/xanthan gum combinations

The objective of this study was to investigate the effect of different pH values (3, 5, 7, 9 and 11) on the stability of Pickering emulsions stabilized by carboxymethyl starch (CMS)/xanthan gum (XG) combinations. The CMS/XG combinations could be used as an effective stabilizer for the preparation of Pickering emulsion. The effects of CMS/XG combinations on oil droplet size, Zeta potential, rheological properties, backscattering profiles, Low-field nuclear magnetic resonance imaging and storage stability of oil-in-water emulsion were evaluated as a function of pH. As pH increased from 3 to 11, the droplet size of the emulsion increased and the absolute value of Zeta potential decreased. Besides, the consistency coefficient of the emulsion was reduced and the pseudoplasticity was weakened. The variation of backscattered light intensity of the emulsion at pH 3 was the smallest. The combination of CMS and XG formed a good network structure and inhibited the phase separation of emulsion. The color distribution of Low-field nuclear magnetic resonance imaging of emulsions at pH 3, 5 and 7 was more uniform and had better storage stability at 25 °C for 9 days. pH affected the aggregation of oil droplets. The Pickering emulsion stabilized by CMS/XG combinations was pH-responsive and could be used as an effective carrier for biologically active substances.