Colloidally stable rice protein-carboxymethyl cellulose complexes tailoring high-protein liquids

Protein-polysaccharide complexation represents a unique paradigm for spatially arranging protein particles to formulate concentrated dispersions. However, this strategy is not applicable to hydrophobic rice proteins (RPs) with low solubility. The objective of this study is to develop a salt-free strategy for preparing high-concentration and stable RP liquids, suitable for high-protein foods. We first prepared uniform RP nanoparticles (29 nm) by cation-exchange resins (CERs) that released H⁺ and replaced Na⁺ while neutralizing OH^- in an alkaline solution. Thus, the generation of NaCl was circumvented eliminating the self-aggregation of RPs. Then, the electrostatic interactions between RPs and an anionic polysaccharide, carboxymethyl cellulose (CMC), were enabled by CER-induced refolding of unfolded RPs. This strategy allowed us to create stable protein-polysaccharide complexes with a protein content up to 6.0 wt%, which were resistant to self-aggregation and had controllable rheological properties that are pivotal for designing high-protein foods.