Study On The Inhibition Methods Of Lipoxygenase By Water Immersion And The Extraction Of Rice Bran Protein From Rice Bran

Based on fresh rice bran as a raw material, in order to improve the storage of rice bran and obtain high-purity rice bran protein, the inhibition methods of lipoxygenase, utilizing alkaline and compound enzymes to extract rice bran protein and functional properties and application were studied systematically. The mainly results were as follows:Water immersion was used to inhibit the activity of lipoxygenase in order to stabilizing treatment of rice bran. The optimal extraction conditions were determined via single factor experiment:By using of the dissolved oxygen0.99ppm of boiling water to prepare the soak solution of5mmol/L citric acid and L-cysteine, material-liquid ratio of1:10, soak temperature of4℃,soak time of2h, the relative activity of lipoxygenase is reduse to10.13%.Utilizing alkaline to extract rice bran protein and the separation of rice bran protein The optimal extraction conditions were determined via single factor experiment. Results indicated that the optimal extraction processing parameters by alkali extraction were extraction temperature of40℃, material-liquid ratio of1:8, extraction time of3.5h, and the highest extraction rate of rice bran protein was44.2%. Measuring isoelectric point of rice bran protein is pH4.6. Crude rice bran protein was purified through10kDa and200kDa ultrafiltration membranes. High purity of rice bran protein was obtained after freeze-drying, and the purity was48.73%.Compound enzymes were used to extract rice bran protein and the separation of rice bran protein. Carbohydrase contains cellulose, phytase and pectase, The optimal extraction conditions were determined via single factor experiment:the cellulose dosage4550U/g, extraction temperature50℃, pH4.8. extracting time was2h. The phytase dosage1200U/g. extraction temperature40℃, pH5.8, extracting time was2.5h. The pectase dosage2430U/g, extraction temperature50℃, pH3.5. extracting time was2h, the exraction rate of rice bran protein reached37.89%. To screen the best modified protease from t he Neutrase, Alcalase, Protamex and Flavourzyme using degree of hydrolysis as indicator. Alcalase was selected as the best extracted protease. The optimal extracted conditions via single factor experiment and orthogonal experiment were:the protease dosage600U/g. temperature55℃, pH8.0, extraction time3.5h, the exraction rate of rice bran protein reached47.13%. Finally utilizing alkaline to extract rice bran protein from residues. Under the above optimal extraction conditions, the exraction rate of rice bran protein reached90.53%, rice bran protein powders were obtained after the purification and the freeze-drying and the purity was70.81%.The rice bran protein’s functional characteristics were studied. After enzymolysis with water immersion to inhibit the activity of LOX. the rice bran protein’s solubility, the foamability and the emulsibility have been improved greatly. Alkaline condition is higher than acidic condition of the protein solubility, and the protein solubility increased with temperature increasing. The rice bran protein’s emulsibility and foamability were higher under the alkalinity condition and they increased with temperature increasing obviously. The results of SDS-PAGE showed that the molecular weight of rice bran protein which is extracted by enzymolysis and though water immersion to inhibit the activity of LOX was between20KDa-120KDa.