Effect Of Adding Extruded Oat Flours On Wheat-oat-dough Properties And Bread Qualities

To investigate the influence of the extruded oat flours on the properties of wheat-oat-dough and quality of bread,oat flours at the gelatinization degree of 17%,36%,54%,73% and 91% were obtained by using non-extruded and extruded oat flours as the ratios of 4:0,3:1,3:3,1:3 and 0:4.The physicochemical properties of different gelatinization degree of oat flours were measured.Different gelatinization degree of oat flours were added to wheat flours as the ratios of 0%,8%,16%,24% and 32%,respectively,to analyze the effect of gelatinization degree of oat flours on rheological properties of wheat-oat-dough.Finally,wheat-oat-flours were used for the preparation of breads,and the physicochemical（specific volume,hardness,hardening rate,water content,acidity）and sensory evaluation of breads were analyzed.The results were as follows:（1）Compared with non-extruded oat flours,the moisture content of extruded oat flours increased,crude fat and crude starch content decreased.The protein content had no significant change.The gelatinization degree of non-extruded and extruded oat flours were 17% and 91%,respectively.（2）The results of physicochemical properties of different gelatinization degree of oat flours were as follows,the color of the oat flours became darkerwith the increasing of gelatinization degree.The damaged starch content,water holding capacity and swelling capacity increased significantlywith the increasing of gelatinization degree,and pH had no significant change.The total sugar content of oat flours decreased,and the reducing sugar content first increased and then decreased with the increasing of gelatinization.The results of thermal characteristics showed that,with the increasing of gelatinization degree,the onset temperature（T_o）and peak temperature（T_p）of oat flours increased,enthalpies（△H）reduced,conclusion temperature（T_c）have no significant change.The peak viscosity,trough viscosity,final viscosity,breakdown and setback decreased with the increasing of gelatinization degree of oat flours;The results of scanning electron microscope（SEM）showed that,the amounts of damaged starch granules of oat flours increasedwith the increasing of gelatinization degree,the intact starch granules were round or oval particles with smooth surface,and damaged starch particles present irregular lamellar structure with rough surface and holes.（3）Accrding to the results of wheat-oat-dough properties,the extensibility of wheat-oat-dough decreasedwith the increasing of gelatinization degree of oat flours;the addition of extruded oat flours had more significantly negative effect on the glutenin microstructure than non-extruded oat flours;The results of thermomechanical properties showed that,the water absorption and stability time of wheat-oat-dough increased,starch viscosity breakdown value,maximum viscosity and retrogradation value decreasedwith the increasing of gelatinization degree of oat flours;The results of rheofermented properties showed that,with the increaseing of gelatinization degree of oat flours,dough maximum height（Hm）and gas leakage time（Tx）reduced,the time of gas release curve maximum height and fermentation stability increased（（Hm-h）/Hm% decrease）,the total CO₂ production first increased and then decreased.（4）The studyfor the influence of different gelatinization degree of oat flours on breads qualities showed that the hardness and water content of breads increased,while the specific volume and hardening rate decreased.There is no significant change in acidity of breadswith the increasing of oat flours gelatinization degree.The highest sensory quality was obtained when the adding ratio of oat flours and gelatinization degree was 16% and 54%,respectively.Therefore,different gelatinization degree of oat flours affect bread qualities in two ways.On the one hand,with the increasing of gelatinization degree,the yield of breads increased,the hardening rate of breads decreased.Aappropriate gelatinization degree can improve the sensory quality of breads.On the other hand,the specific volume and hardness of bread increased with the increasing of gelatinization degree.