LAUSR

The stabilization of interfaces with mixed emulsifiers composed of natural ingredients is of increasing interest in order to modulate stability of food colloids. To this purpose, we first investigated the emulsifying properties of binary emulsifier mixtures composed of natural and food-grade ingredients. We prepared oil-in-water emulsions (10% oil) stabilized by Quillaja saponin-sodium caseinate mixtures at different concentration ratios (r = 5:0, 4:1, 3:2, 2:3, 1:4, 0:5) with the total concentration set to 0.5% and pH set to 7 or 3. Second, we tested the emulsion stability against environmental stresses. The emulsions produced with binary emulsifier mixtures at low Quillaja saponin ratios (r = 2:3 and 1:4, pH 7) showed the best overall performance in terms of generating small and physically stable emulsion droplets similarly to the emulsions stabilized with Na-caseinate or Quillaja saponins alone, whereas at higher Quillaja saponin ratios (r = 4:1, 3:2) the emulsions were unstable. At r = 2:3 and 1:4, the emulsions were also stable at ≤90 °C and ≤200 mM NaCl. Furthermore, they were also stable upon pH change to 2, whereas emulsions stabilized with Quillaja saponins alone (r = 5:0) flocculated. These results demonstrated that the emulsifying properties of mixed binary emulsifiers comprising natural components and subsequent stability of the emulsions is highly dependent on the applied concentration ratio. This study provides valuable insights into the techno-functionality of binary emulsifier systems.