Physico-chemical and structural properties of four rice bran protein fractions based on the multiple solvent extraction method

The physicochemical and structural properties of the concentrated rice bran protein (CRBP) and rice bran protein fractions - RBPF (albumin, globulin, prolamin, and glutelin) were investigated on the basis of multiple solvent extraction method. The protein fractions mainly consisted of essential amino acids except for prolamin. The amino acid composition of concentrated protein was superior to soybean protein isolation, such as valine, methionine, leucine, phenylalanine, and histidine, with similar characteristics of solubility, emulsification, and foaming. Based on the difference in amino acid composition, all these five proteins showed relatively high surface hydrophobicity more than 369.3 of prolamin. CRBP and RBPF were composed of different molecular subunits in SDS-PAGE profile. The circular dichroism spectra (CDS) in synergy showed that the primary structures of RBPF were β-protein folding and random coils with various denaturation temperatures in the range of 78.69°C for glutelin and 92.88°C for globulin. The fluorescence spectrometry assays showed that the blue shift occurred at 348 nm for globulin, while the red shift occurred for the concentrated protein, albumin, and globulin at 356.2, 348.6, and 347.0 nm, respectively. Therefore, the research presents the basic characterisation for further application of natural rice bran protein in the food industry.