Microgel-Stabilized Hydroxypropyl Methylcellulose and Dextran Water-in-Water Emulsion: Influence of pH, Ionic Strength, and Temperature

A stable water-in-water (W/W) emulsion was formed by mixing dextran and hydroxypropyl methylcellulose (HPMC) with addition of β-lactoglobulin (Blg) microgels. The microstructure and stability of the W/W emulsion were investigated under different conditions. The microgels accumulating at the liquid–liquid interface led to a stable emulsion at pH 3–5, where the microgels carried positive charges. When the pH was increased above the pI of microgels (∼pH 5), the emulsion was destabilized because the microgels tended to stay in the continuous phase (i.e., dextran) rather than at the interface. The HPMC-in-dextran emulsions were stable under ionic strength levels up to 300 mM. The HPMC-in-dextran emulsion stabilized by Blg microgels was thermally stable, and the heat treatment promoted partial Blg microgel particle–particle fusion on the surface of HPMC droplets at 90 °C. Electrostatic and hydrophobic interactions between dextran and HPMC phase were further investigated to understand the microgels' accumulation at the liquid–liquid interface.