The formation, structural and rheological properties of emulsion gels stabilized by egg white protein-insoluble soybean fiber complex

In this work, the structural and interfacial characteristics of egg white protein-insoluble soybean fiber (EWP-ISF) complex, as well as the effects of the EWP-ISF ratio and oil volume fraction (phi) on the formation of emulsion droplet-aggregated gels were investigated. EWP was adsorbed onto the surface of ISF matrix at pH 3.2 via electrostatic and hydrogen-bonding interactions. The contact angle significantly increased from 119.3 degrees to 131.5 degrees (p < 0.05) as the EWP-ISF ratio changed from 1:0 to 1:2, simultaneously, the adsorption of EWP-ISF complex at the oil-water interface produced a visible interfacial film. At lower phi of 0.2-0.3, as the EWP-ISF ratio decreased from 2:1 to 1:2, the droplets became finer and the gel-like structure was strengthened; additionally, the relaxation time (T-23) significantly decreased from 622.257 ms to 219.639 ms (p < 0.05), implying the conversion of movable water to bound water. At a higher phi of 0.4-0.5, the droplets were densely packed through bridging flocculation and interactions between droplets and the gel network. Accordingly, the emulsion droplet-aggregated gels stabilized by EWP-ISF presented high elastic modulus and yield stress, as well as excellent thixotropic recovery.