In practical applications, proteins may have to exhibit their desirable functional properties in products that have a wide range of different pH values and ionic strengths. The interfacial membranes formed by proteins are usually relatively thin and electrically charged, hence, the major mechanism preventing droplet flocculation in protein-stabilized emulsions is electrostatic repulsion, rather than steric repulsion [30]. Protein-stabilized emulsions are therefore particularly sensitive to pH and ionic strength effects. They tend to flocculate at pH values close to the isoelectric point of the adsorbed proteins and when the ionic strength exceeds a particular level, because the electrostatic repulsion between the droplets is then no longer sufficiently strong to overcome the various attractive interactions, e.g., van der Waals, hydrophobic or depletion [19] and [31]. Multivalent counter-ions are particularly efficient at promoting emulsion instability because they are more effective at screening electrostatic interactions (reducing the Debye screening length) and because they can bind to droplet surfaces thereby reducing the ζ-potential [32]. The difference in the effectiveness of monovalent (Na+) and divalent (Ca2+) counter-ions at promoting droplet flocculation in a whey protein stabilized emulsion (pH 7) is highlighted in Fig. 2. A variety of strategies have been developed to improve the stability of protein-stabilized emulsions to droplet flocculation induced by pH or ionic strength effects: