| The rice bran protein is known as high quality vegetable protein through the world, it has not only the high nutritional value, but also the low allergic characteristic. China is a large agricultural country which has abundant resources of rice, and has great superiority and potential to develop the projects of rice bran protein. At present, there are many researches and reports about the rice bran protein, but the commercial production of rice bran protein concentration and the rice bran protein isolate had not been achieved in China. The study on extraction of rice bran protein is still at the laboratory stage. The main reasons are that comparing with other vegetable protein, the rice bran protein is hard to extract, and is often following the great deal of colored material production in the process of protein extracting. They made the qualities of rice bran protein to be low, so it does not have good edibility and usability. The browning reaction is the main cause of the product of the color substance. Therefore, this research was based on the results of present researches, preparing rice bran protein with enzyme hydrolysis, optimized the extraction conditions, studied the primary factors of browning and the methods of anti-browning, provide the experimental basis and the beneficial discussion for the high qualitative rice bran protein industrialization.The materials were supported by Agronomy College of Northeast Agricultural University. The rice bran protein was extracted by using cellulose, protamex and phytase with the optimization ratio of them. The response surface method was used to optimize the extract conditions. Taking the protein extraction ratio as the index, degree of hydrolysis as the reference index, the optimization extract conditions were determined. The characteristic of rice bran polyphenol-oxidase was studied and the contents of decreasing sugar, Fe and tannin were determined, the possible browning factor in extracting process was confirmed. Furthermore, based on this, the effect of different methods on the browning inhibition was examed, that is add inhibitors, yeast fermentation to remove glucose, EDTA processing and active carbon decolorize.The results of experiments were as follows.1. The optimum extraction conditions of the rice bran protein by response surface method are: temperature 45℃, substrate concentration 18%, enzyme adding 4733U/g.The test was used to verity the model. The result indicated the testing goodness of it. Under this condition, the protein actual extraction ratio achieves 79.33%, degree of hydrolysis<5%。2. The optimum temperature and pH of the rice bran polyphenol-oxidase were 20℃and pH 6.0 respectively. However, the polyphenol-oxidase is inactivated in 90℃water for 25min. The reducing sugar content is about 8.53%, the tannin content is about 0.81%, the Fe content is 4.8315mg/L. From this, the product of colored substance in the extraction of rice bran protein is mainly affected by enzymatic browning .The results showed that polyphenol-oxidase was basic reason which caused enzymatic browning, the reducing sugar, metal ion and phenols may be the principal reasons of non-enzymatic browning.3. The result showed that the most effective inhibitor combination for enzymatic browning based on orthogonal was 0.15%L-Cys﹢0.30%CA﹢0.010%EDTA-2Na. And the pigment inhibition ratio is 71.06%. In addition, the inhibitors of H2O2 and NaClO also have good effects on non-enzymatic browning. Adding 1.0‰H2O2, the pigment inhibition ratio is 32.30%. Adding 1.0‰NaClO, the pigment inhibition ratio is 34.22%.4. The test indicated that yeast zymotechnics can not remove the reducing sugar in rice bran effectively. Thus, it is ineffective to restrain browning. The treatments of EDTA can reduce the pigment substance. The pigment inhibition ratio is about 13.44%. The results proved that in the conditions: temperature 45℃and decoloring time 20min, the decolourization effect for hydrolyzed rice bran was distinctly, the pigment inhibition ratio is 58.75%.
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