Study On The Effects Of Wheat Bran Fractions On The Formation Mechanism Of Gluten Protein Network

The effects of wheat bran fractions on the dough rheological properties and products qualities of whole wheat system is very complicated.Gluten protein was the main material that influence the quality of flour products,its structures and properties were important to the processing performance of dough and the quality of products.In this study,we addition different amounts of wheat bran,dietary fiber and ferulic acid into wheat flour and investigated their effects on the structures,properties and components composition of gluten proteins.In order to explore the mechanism of bran fractions mediated the formation of gluten network.The results showed that the development time,stability time,water absorption and breakdown viscosity of dough were significantly increased after addition wheat bran and dietary fiber,whereas the effect of ferulic acid on the thermal mechanical properties of dough was small.Except the increase of setback value,the rest parameters of thermal mechanical experiments of dough of 2%FA+6%DF group were had no significant differences compared with the control group.Dry gluten protein contents of dough were significantly decreased as the addition amount of wheat bran and dietary fiber increased,while the FA group was opposite.There was no significant differences of dry gluten protein contents between FA+DF group and control group.The viscoelastic modulus of gluten proteins were obviously increased after addition bran fractions compared with the control group.The tan δ value were significantly decreased as the addition amount of wheat bran and dietary fiber increased,but increased as the addition amount of ferulic acid increased.The results of SDS-PAGE showed that the gluten proteins of wheat bran group were aggregated in the molecular weight range of 55~72KD.The disulfide bonds of gluten proteins were significantly decreased after addition bran fractions,these results were consistent with the changes of △H value and weight loss in the thermodynamic experiment,indicating formation a weaker gluten network after addition bran fractions.Fourier infrared spectrometer showed that addition bran fractions could change the stability and orderly properties of secondary structures of gluten proteins,while addition 2%FA+6%DF into flour had no significant effects on the secondary structure of gluten protein.Scanning electron microscope showed that addition bran fractions could break the uniform and compact three-dimensional network structure of gluten proteins,showing a flaky with jagged edges.However,the microstructure of FA+DF group was more smooth and compact than the DF and FA groups.The effects of wheat bran and FA+DF on the composition of gluten proteins and its components properties were further studied.The results showed that addition wheat bran could decrease the ratio of gliadin and glutenin,while addition FA+DF increase the ratio of gliadin and glutenin.The GMP content of wheat bran group had no significant differences compared with the control group,whereas the GMP content of FA+DF group was decreased.The weight loss of all proteins were significantly decreased compared with the control group,and there may exist some weak chemical bonds between FA+DF and gliadin.Except the disulfide bonds content of GMP in the wheat group increased,all other proteins were decreased.The viscoelastic modulus of GMP were obviously decreased after addition wheat bran and FA+DF compared with the control group,indicating that the GMP gel properties were decreased.The aggregation structure of glutenin protein and the honeycomb structure of GMP were destroyed after addition wheat bran and FA+DF.In conclusion,the mechanism of the interactions of bran fractions and gluten proteins is very complicated.Not only related to the physicochemical properties of bran fractions,but also related to the interactions between bran fractions and the components of flour.Addition bran fractions into flour could change the constitution of gluten proteins and the structure properties of each component.Led to a weaker of gluten network structure and decreased the rheological properties of dough.The adverse effect of bran fractions on the gluten protein and the dough were increased as the addition amounts of bran fractions increased,whereas when addition appropriate proportions of FA and DF(2%FA+6%DF group)could reduce the adverse effects of DF on the gluten network structure and dough rheological properties.