Effect of egg white protein-insoluble soybean fiber interactions on the formation and structural characteristics of low-oil emulsion gels

Emulsion gels with low oil content have attracted increasing interests, and insoluble soybean fibers (ISFs) have been proven to be the potential natural emulsifying stabilizers for emulsion gels. In this work, the structure and characteristics of low-oil emulsion gels stabilized by egg white protein (EWP) and ISF were investigated via tuning interactions between EWP-ISF below, near, or above the isoelectric point (pI) of EWP. EWP was adsorbed onto ISF matrix via electrostatic attraction and hydrogen bonding as EWP-ISF ratio changed from 1:0 to 1:2 below the pI (pH 3.2), resulting in a 3.52 mg/mL decrease in soluble EWP content. EWP-ISF synergistically adsorbed onto the oil-water interface, and the droplets were incorporated into gel matrix via hydrophobic interaction, improving the water-binding capacity and gel structure. The addition of ISF could still improve the gel structure at pH 4.5 despite the weakened interactions of EWP-ISF. However, the competitive adsorption occurred above the pI (pH 7.0), with more ISFs participating in interfacial stabilization; simultaneously the interactions between droplet-gel matrix were weakened, resulting in a decreased gel strength. Overall, ISF improved structural properties of low-oil emulsion gels, which exhibited a higher water-binding capacity and gel strength (14.9 g) at pH 3.2 and EWP-ISF ratio of 1:2.