Soy glycinin-carboxymethyl cellulose “chain bead-like” nanocomplexes: Focus on formation mechanism, functional characteristics and stability properties

In this study, the aim was to solve the problem of poor functional characteristics and stability of soy glycinin (11S). 11S and carboxymethyl cellulose (CMC) nanocomplexes (SCs) were prepared by pH-driven method. They were further analyzed for the effects on the SCs formation mechanism, function and stability properties of CMC concentration (0.05%, 0.1%, 0.5%, 1%, w/v) and degree of substitution (DS, 0.7, 0.9, 1.2). The particle size and zeta potential indicated that the SCs were small in size, uniformly distributed, and high in potential. Classical DLVO theory calculation, FTIR, 3D fluorescence spectroscopy, and UV spectroscopy revealed that 11S and CMC interact mainly through electrostatic forces and hydrogen bonding, and the secondary and tertiary structures of the protein were altered. SEM, AFM and TEM showed that 11S formed “protein nanobeads” and engulfed the “chain” of CMC, generating “chain bead-like” SCs. With the increase in CMC concentration and DS, the hydrophobicity decreased and the molecular flexibility increased of SCs. The solubility, turbidity, emulsifying and foaming properties showed the tendency to enhance and then decrease as the CMC concentration increased; these properties improved better when the DS was stronger. The optimum functional characteristics of the formed SCs were obtained when the concentration and DS of CMC were 0.5% and 1.2, respectively. Furthermore, the addition of CMC significantly improved the pH, ionic stability and thermal stability of the nanocomplexes. This study will provide a theoretical basis for deeper understanding of the mechanism of pH-driven protein-polysaccharide interactions and applications in functional foods.