Effect of heat-induced formation of rice bran protein fibrils on morphological structure and physicochemical properties in solutions and gels

The effects of heat-induced rice bran protein (RBP) fibrils on structure and properties of solutions and gels in a complex system were investigated using transmission electron microscopy (TEM), atomic force microscopy (AFM), Congo red spectral analysis, and circular dichroism (CD). Planar and 3-dimensional images of RBP fibrils all revealed structural details. A Congo red spectral shift indicated fibril formation. Fibril secondary structural components exhibited differences at pH 2.0 and pH 7.0. The beta-type was decreased with an increased pH. Rheological results exhibited shear thinning behavior for all solutions. Addition of fibrils to RBP solutions, which made the system complex, resulted in an order of magnitude increase in viscosity and shear stress. Adding fibrils to RBP solutions accelerated the kinetics of gel formation, resulting in an increase in gel strength. Scanning electron microscopy (SEM) images showed gel network structural differences with and without fibrils at different pH values.