The Effect Of Non-Waxy Rice Proteins On Its Pasting Properties

This paper was aimed at exploring the impact of extracted and binding proteins on non-waxy rice flour pasting properties using different methods.Firstly, the pasting properties of rice flours and reconstituted rice flours from mixing a common starch with proteins extracted from different rice cultivars at different total protein content levels were studied by through separation of recombinant. Results showed the protein variety and total protein content had an effect on the pasting properties of the rice flours. The peak viscosity,final viscosity, breakdown and setback decreased,the hot paste viscosity substantially unaffected,the pasting tempreture increased with the increase of protein content. At the subunit level of the proteins, proteins with a molecular weight of 17,000, most likely from globulin, had the strongest effect on the peak viscosity of the rice flour, followed by those of 33,000.The pasting properties changes of indica rice flours and reconstituted rice flours showed interaction of rice starch and other factors was much bigger than interacting only with larger protein.We studied the pasting properties changes of rice flour by removing protein components one by one.Results showed that the peak viscosity, hot paste viscosity and the final viscosity increased after removing albumin, globin,prolamin and the combination of these three proteins, while the peak viscosity and thermal paste viscosity increased gradually with the increasing of removing components, this was a synergistic effect, but the final viscosity decreased gradually; breakdown, pasting temperature reduced with removing these three proteins,but regular pattern did not exist with the increasing of removing components. The peak viscosity, hot paste viscosity and final viscosity increased after removing gluten,while the breakdown, pasting temperature decreased, and the corresponding changes were significant(P<0.05). In the thermal characteristics, the onset temperature, peak temperature, end temperature and enthalpy reduced after removing albumin, globin, prolamin, the combination of these three proteins and gluten, the onset temperature, peak temperature and end temperature decreased gradually with the increasing of removing components this was a synergistic effect, while the regular pattern did not exist at the end temperature and enthalpy; the corresponding changes were significant(P<0.05) after removing gluten. The changes of pasting properties and thermal properties were consistent with changes in the subunit, apparently 59.30 kDa, 52.41 kDa, 25.11 kDa, 14.90 kDa were not the major factors to lead to these changes,33.29 kDa and 19.90 kDa was the main factors, enthalpy was influenced greatly by starch.To study the impact of the binding protein on indica rice flour pasting properties, Based on the single factor experiments and respose surface analysis, the technology of extracting protein from indica rice yellow starch by thermostable ?-amylase was optimazed. The results demonstrated that the suitable conditions were the volume of enzyme of 4500U/mL, enzymolysis temperature of 95?, hydrolysis time of 4.6h and addition of CaCl2 of 0.086 g/mL. On these conditions, the contraction of protein in the enzymolysis product reached the maximum of 80.52% the protein extraction rate could arrive at 95.42%.By comparison with the rice total protein, the insolubility of protein in yellow starch was about the same, foaming and foam stability were poor.Both foam stability, emulsification, emulsion stability and oil absorption exist significant differences. Also, the banding protein had a significant influence on the yellow starch pasting properties,the main difference of yellow starch after disposed was at 33.60 kDa, 19.74 kDa and 13.87 kDa, after disposed by DTT and neutral protease, 33.60 kDa fell down from 15.37% to 8.86% and 9.37%,respectively, while 19.74 kDa and 13.87 kDa increased 11.73%, 12.9% and 6.57%, 9.45% respectively, the previous studies had confirmed 33 kDa subunit was the major subunit affecting its pasting properties. The presence state of the binding protein in yellow starch gelatinization process: from small protein bodies attached to the cellulose to form a ring-shaped bag and spread out, and then ring-shaped bag breaking down to form a line-like structure.