Protein-based oleogels: effect of ultrasound on the structural characteristics of egg white-rapeseed dual-protein...

As emerging fat substitutes, oleogels are widely recognized for their potential applications in food nutrition and health. In this study, the protein-based oleogel was prepared by oil absorption using egg white (EW) protein microgel and egg white-rapeseed (ER) dual-protein microgel. The microgel was obtained through ultrasound treatment (0-600 W) of the protein system, heating, freeze-thawing, ethanol solvent replacement, atmospheric drying, and ball milling pulverization. This study aimed to explore the effects of protein components and ultrasound powers on hydrogels obtained by heating the protein system, microgels, and oleogels. The results demonstrated that the addition of rapeseed protein increased the surface hydrophobicity of the hydrogel, leading to a lower contact angle of ER₀ microgel (40.45°) than EW₀ microgel (46.54°), and the oil absorption capacity (OAC) of ER₀ microgel was higher than that of EW₀ microgel by 20.75%. The ER₀ oleogel exhibited a higher storage modulus (G') than the EW₀ oleogel. Additionally, the ultrasonic cavitation effect induced protein unfolding and hydrophobic group exposure, enhancing the surface hydrophobicity of ER hydrogel and reaching a maximum at 500 W. The enhanced hydrophobicity improved the lipophilicity of the microgels. Accordingly, the contact angle of ER₅₀₀ microgel decreased to 31.97°, accompanied by the maximum OAC (196.00%). The ER₅₀₀ oleogels displayed predominantly solid-like behavior (G' > G'') with a uniform, dense network microstructure. However, excessive ultrasound power induced protein aggregation, reducing the OAC of ER₆₀₀ to 144.10%. This study provides insights for designing protein-based oleogels using an ultrasound-modified protein system, offering a promising strategy for food applications.