Physical stability and rheological behavior of Pickering emulsions stabilized by protein-polysaccharide hybrid nanoconjugates

This study investigated the emulsifying properties of a protein-polysaccharide hybrid nanoconjugate system comprising cellulose nanocrystals (CNC, 1% w/v) and soy protein isolate at various concentrations (SPI, 1-3% w/v). The average particle size of the nanoconjugate increased, and the zeta potential decreased when 3% (w/v) of SPI was used. The contact angle and thermal stability of CNC improved with the conjugation of SPI. Upon Pickering emulsification, 0.5% (w/v) of CNC-SPI nanoconjugate as particle stabilizer was sufficient to obtain stable emulsions. The CNC-SPI1 formulation (CNC to SPI, 1:1) provided the emulsion with the smallest droplet size and higher emulsifying activity. Intriguingly, ultrasound (US) pre-treatment on nanoconjugates before emulsification significantly reduced the size of the emulsion. The rheological assessment demonstrated that the CNC-SPI-stabilized emulsions exhibit shear thinning behavior at a lower shear rate and shear thickening behavior at a higher shear rate, indicating the interruption of existing attractive interactions between the CNC particles. All emulsions exhibited higher elastic modulus (G′) than viscous modulus (G″), suggesting high viscoelastic properties of the emulsions. This study demonstrates that CNC-SPI nanoconjugate with optimum protein to polysaccharide ratio has great potential as a natural particle stabilizer in food and nutraceutical emulsion applications.