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

Abstract 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.