The Studies On Preparation And Application In Bread Of Modified Rice Bran Protein

Rice bran is the by-product in the process of rice processing,its production and protein is rich.But with much more disulfide bond and surface hydrophobic amino acid residues,etc,its solubility is low under the condition of neutral,which affected its functional properties and application in food.In this paper,the rice bran protein was alkaline extracted jointing with heat and enzymatic modification by using defatted rice bran as raw materials.Then its functional properties,structure and oxidation resistance were studied.Finally modified rice bran protein was used to make bread,evaluating the feasibility of its application in baking food and the effect on bread quality.The rice bran protein was alkaline extracted jointing with heat and enzymatic modification by using fresh defatted rice bran as raw materials and nitrogen solubility index as index.The process was optimized by uniform design.The best condition parameters were as follows: extraction temperature 50 ℃,heat modification time 4 min and enzymatic reaction time 120 min.After the modified,the nitrogen soluble index of rice bran protein reached 96.08%,extraction rate 74.63%,the purity 71.75%.Nitrogen solubility index was significantly increased by 40.63% than before(68.32%)t,which is helpful to the application of rice bran protein in food.By studying the effects of the different modification methods on functional properties of rice bran protein found that water absorption,oil absorption,emulsion,emulsion stability and foamability of combination modified rice bran protein are improved and enhanced in varying degrees,respectively increased by 15.8%,165.7%,165.7%,84.7% and 118.6%,but the foam stability reduced by 22.7%.The mechanism of its functional properties change was studied by determination of free thiol and disulfide bond content of rice bran protein,thermal characteristics analysis,SDS-page electrophoresis analysis and scanning electron microscopy(SEM)analysis.The free thiol and disulfide bond content determination showing that alkaline extracted jointing with heat and enzymatic modification can make rice bran protein disulfide bond content reduce,free sulfhydryl content increased,by making protein hydrolysis to increase the rice bran protein solubility;SDS-page electrophoresis and SDS showed that the molecules of modified rice bran protein changed from large to small,thus it was dissolved in water more easily and its features are improved.DSC showed a decrease in the degree of polymerization of rice bran protein after co-modification.By studying the effects of the different modification methods on rice bran protein antioxidant properties found that the reducing power,DPPH radical scavenging ability,hydroxyl radical scavenging ability,ultra oxygen anion removal ability,ferrous ion chelating ability and the antioxidant capacity in linoleic acid system of modified rice bran protein were different levels improved.Joint modified rice bran protein reduction reached 1.62.IC50 of clearance of DPPH free radical,hydroxyl free radical clearance,ultra oxygen anion clearance and ferrous ion chelating rate were: 6.25 mg/mL,8.20 mg/mL,6.30 mg/mL,5.96 mg/mL.The antioxidant capacity had also been significantly improved in linoleic acid system.The study also found that: high temperature modification can improve the reducing power,ferrous ion chelating ability and the antioxidant capacity of linoleic acid system of rice bran protein,but little influence on the DPPH radical scavenging ability,hydroxyl radical scavenging ability,ultra oxygen anion removal ability.Enzymatic and the joint modification had significant effects on the antioxidant activity.Rice bran protein of different modification methods were used in bread to get the best adding ratio that Alkali to protein 3%,high temperature modified protein 3%,the enzymatic modification protein 3%,combined modified protein 3%.Modified rice bran protein bread and egg white powder bread were compared found that: the bread of the base rice bran protein and enzymatic modification was not better than the bread of egg white powder.but high temperature modified rice bran protein and joint modified rice bran protein was better than egg white powder,joint modified rice bran protein instead of egg white powder is used in bread is feasible.Joint modified rice bran protein used in bread not only improved the quality of bread but also improved the nutritional value of bread,antioxidant activity and the shelf life.