Impact of soy proteins, hydrolysates and monoglycerides at the oil/water interface in emulsions on interfacial properties and emulsion stability

The effect of the adsorption behavior of soy proteins hydrolysates and monoglycerides on the properties of the film at oil-water interfaces in emulsions and emulsion stability was investigated. Surface tension, adsorbed protein composition and interfacial rheological properties were measured to gain insights into the relationships between molecular composition and properties. The interfacial film formed by 7S (β-conglycinin), 11S (Glycinin) and native soy protein isolate (NSPI) exhibited high elasticity due to a high concentration of adsorbed β-subunits, acidic and basic subunits. Soy protein isolate hydrolyzed by pepsin (SPHPe) and soy protein isolate hydrolyzed by papain (SPHPa) had a high percentage of small peptides, less β-subunits and acidic subunits, forming a fluid-like interfacial film at the beginning of the time sweep. Commercial soy protein isolate (CSPI) film without main soy protein subunits induced fluid-like properties. Monoglycerides displaced the small peptides, acidic and basic subunits from the interface and led to fat globule destabilization after 24 h aging. Emulsions were stable with 7S and SPHPe with high proportion of β-subunits, which were not replaced by monoglycerides. This study provided the foundation for the preparation and application of soy protein isolate with different emulsion stability requirements paired with selected enzyme treatments.