Studies On Extraction Of Rice Protein Concentration And Modification Of Rice Protein

In these studies, we extracted rice protein products from rice dregs. We got rice protein concentration(RPC) by washing and de-fatting. RPC was modified by Alclase to obtain rice predigest protein and rice foaming protein. Then some physicochemical properties of RPC, rice predigest protein and rice foaming protein were studied. The main results were listed:(1) The optimum conditions of washing was: temperature 70℃,the ratio of stuff to water was 1 .' 6,washing three times. Under these conditions, concentration of RPC was about 80.5%~82.0%. RPC was defatted by petroleum ether, the optimum process of de-fatting was: temperature 40℃,the ratio of stuff to solvent was 1 : 6, reaction time was 4 hours. The concentration of protein was about 85.0%, extractive rate of rice protein was 85.0%.(2) We got rice predigest protein- by alcalase. The optimum conditions were as follow: enzyme dosage [E]/[S]=0.03AU/g, temperature was 62℃, the ratio of stuff to water was 1 : 10, pH was 7.5 and the reaction time was 5 hours. Under these conditions, extractive rate of rice protein was 52.27% and the concentration of protein was 84.67%. Nitrogen Solute Index(NSI) was above 95% when the pH in the range of 2~12. The foaming and emulsification properties of rice predigest protein were 76% and 48% when the pH was 8.0. SDS-PAGE analysis showed that the molecular weight of rice predigest protein was below 5KDa.(3) Response Surface Methodology(RSM) was used to optimize the preparation conditions of rice foaming protein. The optimum conditions were as follow: enzyme is alcalase, enzyme dosage [E]/[S]=0.01943AU/g, reaction time was 57 minutes, the ratio of stuff to water was 1 : 7.27, temperature was 60℃ and pH was 7.5. Under these conditions, The foaming and emulsification properties of rice foaming protein were 162% and 64% when the pH was 8.0. concentration of protein was 88.05% and extractive rate of rice protein was 34%. NSI was above 90% when the pH in the range of 2-12. The increase of protein concentration, heighten of pH and Na+ both had affirmative effect to the foaming property of rice foaming protein. SDS-PAGE analysis showed that the molecular weight of rice predigest protein was between 2KDa~16KDa. peptide above 5KDa had good foaming capability compared to the molecular weight of rice predigest protein.