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Crude rice bran protein (CRBP) was prepared by alkaline extraction and then treated with 0.6 m HCl to remove phytic acid. The phytate-free rice bran protein (PFRBP) was hydrolysed with proteases M, N, S, P and pepsin under optimal conditions. Hydrolysates obtained from various hydrolysis periods were subjected to analysis for their degree of hydrolysis (DH) and functional properties. The hydrolysates were fractionated by reversed-phase column chromatography on Kaseigel ODS resin (120-140 lm) using a stepwise gradient of aqueous ethanol, and their activities were measured. The 40% ethanol fraction of protease P 4 h-hydrolysate was separated by successive reversed-phase high-performance liquid chromatography and the amino acid sequences of isolated antioxidative peptides were determined by a protein sequencer and matrix-assisted laser desorption ionisation-time of flight mass spectrometry. Crude rice bran protein had higher antioxidative activity than PFRBP, due to the presence of phytic acid. Phytate contents of rice bran, CRBP and PFRBP were 2.5%, 1.42% and 0%, respectively. The activity of PFRBP increased upon protease digestion. Protease M hydrolysates showed the highest DH, but the lowest antioxidative activity. Hydrolysates with DH below 10% had higher antioxidative activity than those above 20%. This result indicates that the antioxidative activity of the hydrolysates is inherent to their characteristics amino acid sequences of peptides depending on the protease specificities.

The development of degradable and edible films from protein sources has drawn significant attention for the utilisation of natural resources as well as for the alleviation of the environmental burden. Rice bran protein (RBP) was applied to protein film preparation in this study. The protein solutions were casted on plastic tissue culture dishes with glycerol as a plasticiser after heat treatment. Functional properties of the films were then measured. The puncture strength (PS) of RBP films increased up to pH 8.0 and then decreased. PS of protein films depends on the degree of protein purity, quality and composition. Higher concentration of glycerol weakened the films. The pH affected the water solubility of RBP films and the films showed least solubility at pH 3.0. RBP could be utilised in the preparation of degradable protein-based films. The RBPbased film had functional properties comparable to those of the soy protein-based ones.

Rice bran contains 120-200 g kg −1 protein in addition to a large amount of fat, carbohydrate, and phytic acid. Rice bran protein (RBP) fractions were refined by a two-step preparation to eliminate residual carbohydrate. The first step involved the sequential extraction of defatted rice bran into RBP fractions using their distinct solubility to give 37 g kg −1 of albumin, 31 g kg −1 of globulin, 27 g kg −1 of glutelin, and 2 g kg −1 of prolamin. In the second step, carried out by dissolving in respective solvent and isoelectric precipitation, the protein content of each fraction increased from 69% to 97% for albumin, from 71% to 90% for globulin, from 74% to 83% for glutelin, and from 18% to 20% for prolamin. The low protein content in the prolamin fraction might be due to its low solubility in the protein assay. Emulsifying stability index and surface hydrophobicity increased in the second-step preparation of albumin and globulin, but not of glutelin. Emulsifying properties of RBPs were lower than that of a soybean protein isolate. Denaturation temperatures and enthalpy values of denaturation for albumin, globulin, glutelin, and prolamin were 50.1• C/1.2 J g −1 , 79.0 • C/1.8 J g −1 , 74.5 • C/3.0 J g −1 , and 78.5• C/8.1 J g −1 , respectively. No significant differences in the denaturation temperatures and enthalpy values of denaturation of RBP fractions were obtained with these two-step preparations (P < 0.05).