| The yield of China's rice is the first in the world, but the scale and processing technology is far away from the developed countries. Rational development and utilization of early indica rice,broken rice,rice residue and other industrial by-products with poor quality ,which can provide quality for high nutrition, increase added value, gain great social and economic benefits. Rice protein is recognized as a quality plant protein with high biological potency and low hypoallergenic, confirmed to have better composing of essential amino acids. Unfortunately, about 80% of the rice protein contained is glutelin with very low solubility, which limited the application in the food industry. The study use rice protein proteolysis and graft copolymerization technology to improve the functional properties of rice protein with high solubility and enhance the application value, providing a theoretical reference for high hydrophobicity of modified plant proteins.Using alkaline extraction and acid precipitation extracted from the broken rice protein, determined by orthogonal experiments which provided the best base parameters were: alkali concentration of 0.06mol/L, 1:8, 2h, in this conditions, the alkali extraction and acid precipitation rate of protein was 75.84%, protein content up to 85%. The impact factors and response surface analyzed optimize that the better process conditions for rice protein proteolysis with alkali protease are as follows: 55℃, 3 h, pH 8, rice protein concentration 5% and the ratio of enzyme/protein 1.5%. Rice hydrolyzed protein with relative molecular mass was between 300 and 2500 occupied 78.21%, the nitrogen recovery can get up to 70.44%, solubility can be modified before the 6.67% to 92.88%, emulsifying and emulsion stability, foaming capacity and foam stability were 0.445, 84.77, 158.30% and 82.20%, which before hydrolysis were 13.92 times, 3.07 times, 2.26 times, 1.07 times and 1.21 times, the functional properties got a better improvement.Through the hydrolysis process on the improvement of the rice protein solubility effect was very significant, but there were about 40% of the protein hydrolysis process not improved their functional properties. Using polysaccharide graft technology to this part of the protein was modified to analyze the protein- carbohydrate ratio, reaction time, not temperature, pH and other conditions on the wet grafting reaction, the solubility index single factor experiments and response surface optimization to determine enzymes residue protein-dextran grafted optimum conditions: protein ratio of 2:1 with the sugar, at 90.0℃, pH to 11.66 for 16.8 min, the graft degree of the complex was 31.71%, the protein content was 37.28%.The influence of different pH, temperatures and concentrations of enzyme residue protein-dextran complex functional properties, which compared with the enzyme protein residue. The results showed that: grafting degree was 31.71% ,the solubility with enzyme residue protein-dextran grafted complex at pH7 is 71.42% when the emulsifying and emulsion stability was 0.482 and 47.51, foaming and foam stability was 94.50%, 95.74%, respectively the 8.29 times, 2.65 times and 2.99 times, 1.79 times and 1.84 times of enzyme residue proteins; the comprehensive study on the rice protein modification achieved very significant results.There is the first use of zymohydrolysis and graft comprehensive technology to modify rice protein, the solubility of the hydrolysates and dextran graft could reach over 90%, 70% respectively, the emulsification and emulsion stability, foaming capacity and foam stability have been well improved. |
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