Study On The Conjugate Of Rice Bran Protein And Polysaccharide And Its Structural,Functional And Effect On Freeze-Thaw Properties Of Frozen Dough

In this study,rice bran protein(Rice Bran Protein,RBP),dextran and arabinoxylan were used as the main raw materials to prepare the rice bran protein-polysaccharide conjugates product by the wet heat method.The optimum process conditions were determined by single factor and response surface methodology.The structural and functional characteristics of the rice bran protein after graft modification were analyzed and compared by various means.The effects of different polysaccharides on the structural and functional properties of rice bran protein conjugates were investigated.The antifreeze protection effects of two groups of rice bran protein-polysaccharides conjugates on frozen dough were studied for the first time.The main results were as follows:1.Process optimization of glycosylation modified rice bran protein by the wet heat method.Using the degree of the grafting as the response value,Based on the single factor and response surface optimization experiments,the four factors of grafting solution pH,grafting reaction time,polysaccharide-rice bran protein mass ratio,and grafting reaction temperature were optimized.The process conditions of arabinoxylan modified rice bran protein were obtained as follows: pH 10,the grafting reaction time was 48 min,arabinoxylan to rice bran protein mass ratio was 2.2:1,the grafting reaction temperature was 50?,and the degree of the grafting was verified by experiments to reach 34.01%.The process conditions of dextran modified rice bran protein were obtained as follows: pH 10,the grafting reaction time was 40 min,dextran to rice bran protein mass ratio was 2.3:1,the grafting reaction temperature was 44?,and the degree of the grafting was verified by experiments to reach 38.61%.The mixtures and conjugates of arabinoxylan,dextran and rice bran protein were named RBP-A,RBP-D,RBP-AC,RBP-DC,respectively.2.Comparison of structural and functional properties of rice bran protein before and after graft modification.Scanning electron microscopy results showed that the surface structure of the modified product became loose.Compared with the RBP-AC,the surface structure of the RBP-DC became more porous.Fourier transform infrared spectral results confirmed that both polysaccharides were covalently bonded to rice bran protein,and the hydroxyl characteristic peaks of RBP-DC were more obvious,indicating that the introduction of polysaccharides increased the content of hydrophilic groups.Amino acid analysis and SDS-PAGE results showed that rice bran protein covalently condensed with dextran and arabinoxylan,respectively.Circular dichroism showed that the ?-helix content of RBP-AC and RBP-DC both decreased,while the ?-turn,?-sheet and random coil content increased,confirming the disordered structure content of the modified rice bran protein increased.The surface hydrophobicity results showed that the hydrophobicity of both RBP-AC and RBP-DC decreased.The modified rice bran protein also improved the solubility,thermal stability,emulsification characteristics,foaming characteristics,water holding capacity and holding capacity to varying degrees.However,the functional properties of RBP-DC were better than RBP-AC.The smaller the relative molecular weight of the polysaccharide,the higher the degree of grafting,and the more obvious the modification of the functional properties of the grafted product.3.Effect on the freeze-thaw properties of dough by graft-modified rice bran protein.Adding modified rice bran protein can increase the deep-bound water content of the dough,increase the hardness,viscosity,and chewability of the dough,and improve the water absorption performance of the dough.It shows that RBP-AC and RBP-DC can inhibit the recrystallization of water in dough caused by freezing treatment.The rheological results show that the addition of RBP-AC and RBP-DC can slow down the increase of tan? of the dough.It was shown that the rice bran protein-polysaccharide conjugate can act as a frozen dough improver,and the conjugates had freeze-thaw stability.And adding RBP-DC with high grafting degree has better effect.