Effects Of Adding Extruded Gelatinized Tartary Buckwheat Flour On Propertiesof Wheat Dough

In order to study the effects of adding extruded gelatinizedtartary buckwheat flour on the properties of wheat dough,this paper selects tartary buckwheat as raw material,gelatinization degree of 37.7%,56.3%,74.3% and 94.2% of tartary buckwheat flour were obtained by single-screw extrusion machine,the changing relationship betweengelatinization degree on and physicochemical properties of tartary buckwheat flour and rheological properties of tartary buckwheat dough were analyzed;In addition,extruded gelatinized tartary buckwheat flour were added to wheat flour,the effects of gelatinization degree and the amount of extruded gelatinizedtartary buckwheat flour on the rheological properties of wheat dough were investigated;Wheat starch and wheat gluten were used to simulate the gluten network structure of wheat dough,the effects of extruded gelatinized tartary buckwheat flour and different gelatinization degree of tartary buckwheat starch on gluten structure of wheat dough were studied.The results are shown as follows:(1)the main chemical constituents,pasting properties,hydration properties,thermodynamic properties,and the microstructure of tartary buckwheat flour were analyzed.The results showed that with the increasing of gelatinization degree,the contents of total flavonoids and lipid reduced significantly(P>0.05),the contents of damage starchincreased significant,and the color of the flour became darker,while the contnens of starch,ash and protein showed no significant change(P<0.05);the water absorption index(WAI)and water retaining capacity also increased significantly(P>0.05);The significant downtrends(P>0.05)of trough viscosity,final viscosity,setback,and peak time were observed;T0 and Tp increased(P>0.05),but ?H dramatically reduced(P>0.05),when gelatinization degree was increased.the particles of tartary buckwheat flour was round or irregular polygon particles with smooth surface,while the extruded ones had no definite shape and the surface became rough with cracks and holes.The rheological and microstructures of tartary buckwheat dough were observed by texture analyzer,SEM and CLSM.The results showed that the hardness,residual stress E2,damping coefficient ? and relaxation time? of tartary buckwheat dough increased first and then decreased,and were higher than those of untreated tartary buckwheat flour.Cohesivenness,elasticity,chewiness,recovery,resistance to extensionand extensibility were significantly increased.When the gelatinization degree reached 94.2%,the elasticity of the dough increased from 0.14 to 0.92,the cohesivenness increased from 0.11 to 0.78,? increased from 19.42 to 32.53,and the extensibilityincreased from 2.63 mm to 10.05 mm.Indicating that the extrusion treatment can significantly improve the texture of tartary buckwheat dough.The microstructure of the dough shows that the starch granules on the dough surface are reduced and the structure is more compact with the increasing of gelatinization degree.When the starch is completely gelatinized,the starch in the molten state forms a continuous cross-linking structure.(2)The addition of extruded gelatinized tartary buckwheat flour(Gelatinization degree of 94.2%)had a great effect on the properties of wheat flour.With the increasing of the proportion of extruded gelatinized tartarybuckwheat flour,the hydration characteristics of the mixed flour increased,the gelatinization viscosityand the enthalpy decreased.The rheological properties of the dough were analyzed,the results showed that cohesivenness,elasticity,chewiness,recovery,the relaxation time and resistance to extension of the dough were gradually increased,extensibility decreasedfrom 22.64 mm to 13.97 mm.SEM showed that the addition of tartary buckwheat flour destroyed the gluten protein network structure,and with the increasingof the content,the gelatinized gel increases and the dough binds more closely.(3)The different gelatinization degree of tartary buckwheat flour and wheat flour were mixed at a ratio of 6:4,found that gelatinization degree of tartary buckwheat flour had a great influence on the physicochemical properties of tartary buckwheat-wheat flour and the rheological properties of dough.With the increasing of gelatinization degree of tartary buckwheat flour,the hydration characteristics of the mixed flour were significantly enhanced,T0 and Tp increased,Tc-T0 and ?H were significantly reduced.Compared with the control group,low gelatinization degree of tartary buckwheat flour had no significant effect on the pasting property of the mixed flour,and the pasting property of the mixed flour was improved obviously when gelatinization degree reached 94.2%.In addition,the cohesiveness,elasticity,chewiness,recovery,relaxation time and resistance to extensionof dough increased gradually with the increasing ofgelatinization degree,while extensibility decreased significantly.SEM showed that the structure of wheat gluten was obviously destroyed with the increasing of gelatinization degree,the starch granules on the dough surface were less and the dough was more compact.(4)Extrudedgelatinizedtartary buckwheat flourwas added to wheat model dough,found that with the increasing of the content of tartary buckwheat flour and increase of gelatinization degree,the gluten structure in the dough decreased,the gelatinized starch increased,and the more obvious the cross-linking structure was formed,which indicating the dough property improvement is mainly the role of gelatinized starch.The microstructure of tartary buckwheat starch with different gelatinization degreeand gluten protein was analyzed.When gelatinization degree was less than 37%,the tartary buckwheatstarch had no significant effect on the gluten network structure.When the gelatinization degree was high,the gelatinized starch could destory gluten network formation,while gluten protein had some influence on the formation of the cross-linked structure of gelatinized starch.