Studies On Rheological Properties Of Gluten-free Dough Based On Buckwheat Flour And Zein

Gluten is a wheat gluten protein,Celiac disease is also known as gluten allergy,and patients can only eat gluten-free foods.The lack of gluten protein network structure in gluten-free foods leads to difficulties in processing and poor taste.The introduction of exogenous structural proteins is one of the ways to improve the poor structure of gluten-free products.Zein as a gluten-free modifier can provide good structural support for gluten-free products.As an important grain crop in China,buckwheat has high nutritional value and is deeply loved by the people.Using buckwheat as the base powder of gluten-free cereal noodles can expand the buckwheat consumption market.In this study,the thermodynamic properties and pasting properties of different proportions of mixed flour were studied by using buckwheat flour and airflow puffed tartary buckwheat flour as base materials.The buckwheat gluten-free dough（referred to as’buckwheat dough’）was prepared according to different proportions of tartary buckwheat flour and common buckwheat flour and different water addition amounts.The texture,tensile and stress relaxation characteristics were studied to obtain the basic formula.Then,the effects of adding Zein and glycerol（plasticizer）on the static rheological properties（texture properties,tensile properties and stress relaxation properties）,dynamic rheological properties,optical properties（chroma and reflectance）and microstructure of buckwheat dough were investigated.Finally,Zein-buckwheat gluten-free noodles were prepared,and their water absorption,broken rate,cooking loss rate,soup turbidity,texture and tensile properties were investigated.The following results were obtained:（1）The tartary buckwheat seeds extruded by high temperature and atmospheric pressure airflow enhanced the combination of water and starch,and improved the water retention of tartary buckwheat powder.The stability of starch granule structure and anti-gelatinization can be enhanced by mixing buckwheat powder with airflow puffed buckwheat powder.With the increase of the proportion of tartary buckwheat powder,the gelatinization enthalpy of the mixed powder decreased significantly,and it was uniformly dispersed in the aqueous solution.When the ratio of tartary buckwheat flour to common buckwheat flour was 5∶5 and the amount of water added（based on dry flour）was 110%,the maximum tensile strength and maximum tensile distance of buckwheat dough were the largest,the hardness was 482.31 g,the elasticity was 0.21,and the damping coefficient was 54.90 N·m^-2·S·10^-6.At this time,the ductility of buckwheat dough was better,which was convenient for subsequent processing.（2）When the addition amount of Zein increased from 0%to 20%,the hardness of buckwheat dough decreased from 482.38 g to 346.60 g,the elasticity increased from 0.21 to0.29,the tensile distance increased from 15.44 mm to 38.16 mm,and the tensile resistance increased from 13.10 g to 72.04 g.The residual stress,viscoelastic coefficient and relaxation time of buckwheat dough were significantly higher than those of the control group,but gradually decreased with the increase of Zein addition.The G’and tanδvalues,surface brightness and reflective rate were significantly improved.Compared with the control group,the microstructure of buckwheat dough can be clearly observed.The above results fully indicate that Zein can effectively improve the binding force and extensibility of buckwheat dough.（3）When the addition of glycerol was 10%and 20%,the hardness of buckwheat dough increased.When the addition amount was 30%and 40%,the hardness decreased and approached the wheat dough,and the elasticity decreased but there was no significant change between different levels.The maximum tensile strength was 205.20 g when the amount of glycerol was 10%.With the increase of glycerol,the tensile strength decreased to 113.56 g,and the tensile distance increased from 48.48 mm to 63.34 mm.The residual stress and damping coefficient of buckwheat dough treated with glycerol were significantly increased,and the G’and tanδvalues,surface brightness and reflective rate were significantly improved.The microstructure was thinner than that of the control group without glycerol treatment,and the tensile distance was gradually increased.Therefore,glycerol can further improve the structure of buckwheat dough.（4）When the addition amount of Zein was 5%,the breaking rate,water absorption rate,cooking loss rate and absorbance of buckwheat gluten-free noodles were the best in the experimental group and better than the control group,but with the increase of Zein,the above indexes increased and the cooking characteristics were poor.The hardness of buckwheat noodles increased from 2825.07 g to 3687.13 g with the increase of Zein,and the elasticity decreased from 0.65 to 0.44,indicating that the texture characteristics of Zein noodles became worse and the chewiness decreased after cooking and cooling.The tensile force of noodles increased from 71.83 g to 112.44 g,and the tensile distance increased from 6.83 mm to 8.85mm.In summary,appropriate amount of Zein can effectively improve the cooking characteristics and texture characteristics of buckwheat gluten-free noodles,and some indicators are close to wheat noodles.Through the above research,it can be seen that the addition of Zein can effectively improve the processing characteristics of gluten-free buckwheat dough.Glycerin pretreatment of Zein can also effectively improve the ductility of Zein itself.Appropriate amount of Zein has a good effect on the cooking characteristics of buckwheat gluten-free noodles.This study provides basic data support for the research of Zein in food and provides a theoretical reference for the development of gluten-free products.