Rice bran protein is increasingly considered as an alternative and cheap source of plant-based high-quality protein. However, commercial rice bran protein is still unavailable in the market. In this study, sequential extraction followed by characterization of rice bran protein (RBP) from defatted rice bran of BR11 and BRRI dhan28 was conducted based on the differences in proteinsÂ’ solubility. Two extraction methods were investigated. Method 1 involved the isoelectric and acetone precipitation using distilled water, 50 g kg-1 NaCl, 0.02 mol L-1 NaOH, and 70% ethanol as extracting solvents for albumin (pH 4.1), globulin (pH 4.3), glutelin (pH 4.8), and prolamin, respectively. In method 2, dialysis and sequential extraction were carried out with 20 g kg-1 NaCl, 70% ethanol, and 0.02 molL-1 NaOH solutions as extracting solvents. Proximate composition, functional properties, and amino acid composition were analyzed to explore the properties of rice bran protein (albumin) for future applications. Based on the total yields (protein) and data obtained from both methods, method 1 was chosen for the isolation and characterization of FRBPs. Rice bran protein fractions (RBPFs): albumin, globulin, glutelin and prolamin, and the total protein content were obtained in good yields by method 1 for both rice varieties. The albumin extracted from BRRI dhan28 showed better functional properties and proximate composition (except ash) compared to that from BR11. Based on the amino acid profile, BRRI dhan28 contained higher amount of essential and non-essential amino acids than BR11. Similar higher yields of crude protein were also found regarding proximate composition and different functional properties (except ash) in BRRI dhan28 than in BR11. The highest hemagglutinating activity was observed in albumin. Rice bran can be a good source of albumin protein and is also suggested for use as a potential food fortification compound.
Key words: Defatted rice bran, sequential extraction, albumin, essential amino acids, hemagglutinating activities
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