Characterization of bacterial cellulose nanofibers/soy protein isolate complex particles for Pickering emulsion gels: The effect of protein structure changes induced by pH

In this work, the influence of soy protein isolated at different pH values (1-9) on the self-assembly behaviors of bacterial cellulose nanofibers/soy protein isolate (BCNs/SPI) colloidal particles via anti-solvent precipitation were investigated. The results showed that the formation of BCNs/SPI at pH values of 1-5 was mainly driven by electrostatic interaction, while the formation of those at pH values of 5-9 was driven by weak molecular in-teractions including hydrogen bonding and steric-hindrance effect. The FTIR demonstrated that the conformation of protein involved a transition from order to disorder at the level of secondary structure as pH values were away from the isoelectric point. The fluorescence spectroscopy and UV-vis adsorption spectroscopy indicated that hydrophobic region of SPI at pH value of 5 displayed more exposed as compared with that at pH values away from the isoelectric point. The changes in structure conformation of SPI induced by pH values led to the changes in properties of the BCNs/SPI colloidal particles including particle size, microstructure, crystallinity, hydrophily, thermal stability, and rheological properties. Furthermore, the structures of BCNs/SPI colloidal particles at different pH values significantly affected the stability of Pickering emulsion gels stabilized by the corresponding complex colloidal particles. This study provided a theoretical basis for the design of food-grade Pickering emulsion gels stabilized by BCNs/SPI complex colloidal particles.

Automated summary

This study investigated the influence of soy protein isolated at different pH values on the self-assembly behaviors of bacterial cellulose nanofibers/soy protein isolate colloidal particles. The results showed that the formation of the colloidal particles was mainly driven by electrostatic interaction at pH values of 1-5, while weak molecular interactions including hydrogen bonding and steric-hindrance effect played a role at pH values of 5-9. Changes in protein conformation and hydrophobic exposure were observed with different pH values, leading to variations in properties of the colloidal particles. The structures of the colloidal particles significantly affected the stability of Pickering emulsion gels. This research provides a theoretical basis for designing food-grade Pickering emulsion gels stabilized by the complex colloidal particles.