Role of Postadsorption Conformation Changes of β-Lactoglobulin on Its Ability To Stabilize Oil Droplets against Flocculation during Heating at Neutral pH

The influence of heating on droplet aggregation in hydrocarbon oil-in-water emulsions stabilized by a globular protein was examined using laser diffraction. Different levels of salt (0 or 150 mM NaCl) were added to n-hexadecane oil-in-water emulsions stabilized by β-lactoglobulin (β-Lg, pH 7.0) either before or after isothermal heat treatment (30−95 °C for 20 min). At 0 mM NaCl, no aggregation was observed in any of the emulsions because of strong electrostatic repulsion between the droplets. At 150 mM NaCl, droplet flocculation occurred between 30 and 65 °C due to surface denaturation of β-Lg after adsorption. Above 70 °C, droplet flocculation became less extensive when 150 mM NaCl was added to the emulsions after heating but more extensive when the salt was added before heating, which was attributed to thermal denaturation of adsorbed β-Lg. When the droplets are in close proximity during heating (150 mM NaCl), interactions between proteins adsorbed onto different droplets are favored, but when droplets ...