Rancidity-induced protein oxidation affects the interfacial dynamic properties and the emulsion rheological behavior of rice bran protein

To improve the practical application of rice bran protein (RBP) prepared from rice bran (RB) with different degrees of rancidity as a stabilizer in emulsion, fresh RB was stored for 0, 1, 5, 7, and 10 d (temperature of 25 °C, relative humidity of 85%) to investigate the effects of RB rancidity on the interfacial dynamic properties and structures of RBP, rheological properties of the O/W emulsion prepared by RBP. RB rancidity-induced moderate oxidation of RBP (prepared from RB storage for 1 d) reduced the particle size (24.36–18.17 nm) and Zeta potential (−13.57 ∼ −14.97 mV) of RBP, while excessive RBP oxidation (prepared from RB storage for 5–10 d) increased the particle size (37.84–68.06 nm) and Zeta potential (−13.40 ∼ −10.6 mV) of RBP. In addition, moderate protein oxidation increased the interfacial pressure, diffusion rate, interfacial expansion modulus of RBP, and emulsion viscoelasticity, while excessive protein oxidation improved the permeability rate and rearrangement rate of RBP. Overall, this study demonstrated that moderate protein oxidation had positive effects on interfacial properties (interfacial dynamic properties and dilatational rheology of interfacial layers) of RBP, which could provide a theoretical basis for mediating the stability and rheology of RBP emulsions by adjusting the degrees of RB rancidity.