Solubilization of Water-insoluble Subunits in Rice Proteins by Freeze- milling

This study investigated the effects of freeze-milling on the structural and functional properties of rice proteins (RPs). Sodium dodecyl sulfate–polyacrylamide gel electrophoresis showed that freeze-milling slightly influenced the subunit bands of RPs. Secondary and tertiary structures were studied by analyses of Fourier transform infrared spectra, sulfhydryl and disulfide bond contents, and surface hydrophobicity. 10 The freeze-milled RPs (FMRPs) may possess an unfolded conformation with exposed buried functional groups. In addition, the solubility of the FMRPs was higher than that of the control probably because of the exposure of water–protein interaction areas. Particularly, the solubility of the FMRPs treated at pH 12.5 was 42 times that of the control. Characterization of functionalities displayed that both emulsifying and foaming activities of FMRPs were improved by solubilization. However, functional stabilities were 15 unaffected or deteriorated. Generally, the FMRPs showed better emulsifying activity and stability than bovine serum albumin while better foaming activity and stability than hen egg albumin. FMRPs may be of great interest to the food industry.