Influence of molecular structure and interface behavior on foam properties of rice bran protein nano-particles

According to our previous research, thermal-acidic treatment was an effective way to improve foaming properties, especially foam stability, of rice bran protein (RBP) samples. In this article, the molecular structure and interface behavior of native RBP and rice bran protein nano-particles (RBPNs) were characterized to illustrate the relevant mechanisms affecting foaming properties. The circular dichroism (CD) and intrinsic fluorescence measurements suggested that thermal-acidic treatment could increase the flexible conformation of RBPNs corresponding to a higher surface activity at the interface. The decrease in apparent viscosity of RBPNs also illustrated the improvement in foam capacity of RBPNs. Moreover, the studies of air-water interfacial behavior demonstrated that the interfacial interaction of RBPNs-1 behaved stronger resulting in forming a stronger and more stretchable interfacial viscoelastic film compared to native RBP, which was mainly related to the different intermolecular interactions at the interface between the RBPNs-1 and native RBP. Further, combined with the analysis of the foam microstructure, it could indicate that in addition to the effects of the interface film on foam stability, the RBPNs trapped in Plateau borders provided the jamming effect by impeding the flow and reducing the rate of drainage. These findings are helpful to understand the relationship between molecular structure, interface behavior, and foaming properties.