Study On Improvement Of Whole Wheat Dough And Its Influence On Quality Of Whole Wheat Based Foods

Whole wheat flour contains endosperm,bran and germ,and is rich in dietary fiber and many trace elements.Long-term consumption can effectively prevent the occurrence of chronic diseases such as diabetes and cardiovascular disease.However,the existence of a large amount of fibers in whole wheat flour leads to the decline of the taste,texture and overall consumer acceptability of whole wheat food.In order to improve the quality of whole wheat food,firstly,xylanase,transglutaminase(TG),diacetyl tartrate monoglyceride(DATEM)were added to the whole wheat flour,and the dough mixing characteristics,rheological properties,tensile properties,microstructure,and protein changes were investigated by Mixolab,texture analyzer,dynamic rheometer,laser confocal electron microscope and SDS-PAGE.Their effects on the quality of whole wheat steamed bread were also studied.The results showed that xylanase decreased the water absorption,development time,stability time,peak viscosity,tensile strength,elastic modulus(G’)and viscosity modulus(G ")of wheat dough,but the extensibility of wheat dough increased.TG enzyme decreased the water absorption of whole wheat dough,but increased the dough development time.The dough stability time first increased then decreased,the peak viscosity increased,and the setback value decreased.The development time,stability time and setback value of whole wheat dough increased and the peak viscosity decreased with addition of DATEM.TG enzyme and DATEM increased dough tensile strength,G’ and G",but decreased dough extensibility.Xylanase can degrade water-insoluble polysaccharides,while TG and DATEM can induce protein molecules to aggregate and cross-link,which makes gluten structure more continuous and improves the microstructure of whole wheat dough.The addition of xylanase and DATEM significantly reduced the hardness,increased the specific volume and effectively improved the quality of whole wheat bread.Secondly,egg white powder(EW,0-7.0%)and sodium caseinate(SC,0-7.0%)were added into whole wheat flour.The effects of exogenous protein addition on the dough mixing characteristics,rheological properties,microstructure and the quality of whole wheat bread were studied.It was found that with the increase of EW addition,the water absorption of whole wheat dough gradually decreased,the development time and stability time of dough gradually increased.The degree of protein weakening was lower than that of whole wheat control but higher than that of whole wheat with addition of 3.0% gluten(G3.0)control.During the heating and cooling process,the peak viscosity and setback value of the dough gradually increased;with the increasing addition of SC,the water absorption of whole wheat dough gradually increased,the development time and stability time of dough gradually increased.However,when the content of SC was higher than 3.0%,it began to decrease;In addition,when the content of SC was higher than 5.0%,the peak viscosity of the dough decreased,and the setback value increased;The results of rheological properties showed that EW decreased the viscoelasticity of the whole wheat dough,while SC increased the viscoelasticity of the whole wheat dough when the content of SC was higher than 1.0%;EW and SC both improved the the microstructure of the dough,making the dough structure uniform and continuous,which effectively reduces the hardness of the whole wheat bread.However,when the SC content is too high,the dough strength increased rapidly,leading to lower specific volume of and higher hardness of bread.Finally,potato starch was modified by extrusion technology.The extrusion temperature was set at 60 ℃ and 90 ℃,and the water content was at 30%,42% and 54%.The gelatinization degree,water absorption index(WAI),water solubility index(WSI),static rheological and gelatinization characteristics(RVA)of modified potato starch were measured.10% extrusion modified potato starch was added to whole wheat flour,and the effects of modified potato starch on the dough mixing characteristics,tensile properties,rheological properties,microstructure and the quality of the whole wheat fried bread stick were studied.The results showed that the modified potato starch had higher degree of gelatinization,water absorption and water solubility than that of the original potato starch,which made it easier to form gel.The static rheological test showed that the high temperature or low moisture extrusion-modified starch had higher cold paste viscosity when mixed with water.At the same extrusion temperature,The peak,trough,breakdown,final viscosity,and setback value increased with the increase of barrel water content.With the addition of 10% extrusion modified potato starch,dough water absorption increased,while development time,stability time,peak viscosity and setback value significantly decreased.The tensile strength and tensile distance of wheat dough increased due to the stickness and gelation properties of modified starch.The modulus of elasticity(G’)and viscosity modulus(G")of whole wheat dough with high temperature extrusion modified potato starch were higher than those with low temperature extrusion modified potato starch.Three treatments of modified starches,i.e.60-30,60-42 and 90-42,can effectively reduce the hardness and increase the specific volume of fried bread stick.As a word,modified potato starch with different viscosity and gel properties could be obtained by varying the extrusion conditions,which might be applied to improve the quality of whole wheat dough and whole wheat based food.