Fibrillation modification to improve the viscosity, emulsifying, and foaming properties of rice protein

Fibrillation of food proteins has attracted considerable attention as it can improve and broaden the functionality of proteins. In this study, we prepared three kinds of rice protein (RP) fibrils with different structural characteristics by the regulation of NaCl and explored the effect of protein structure on viscosity, emulsifying, and foaming properties. AFM results showed fibrils formed at 0 and 100 mM NaCl were mainly in the range of 50-150 nm and 150-250 nm, respectively. Fibrils formed at 200 mM NaCl were in the range of 50-500 nm and protein fibrils longer than 500 nm increased. There was no significant difference between their height and periodicity. Fibrils formed at 0 and 100 mM NaCl were more flexible and unordered than those formed at 200 mM NaCl. The viscosity consistency index K of native RP and fibrils formed at 0, 100, and 200 mM NaCl were determined. The K value of fibrils was higher than that of native RP. The emulsifying activity index, foam capacity and foam stability were enhanced by fibrillation, while longer fibrils exhibited lower emulsifying stability index, which may be because long fibrils resulted in difficulty of cover of emulsion droplets. In summary, our work provided a valuable reference for improving the functionality of rice protein and facilitated the development of protein-based foaming agents, thickeners, and emulsifiers.