| Wheat flour can form dough,of which gluten protein and wheat starch are the most important components.As both gluten protein and wheat starch are macromolecular compounds,the interaction between them is complex.In production and processing,a series of factors,such as Na Cl,temperature,etc.,will affect the interaction between gluten protein and wheat starch.In order to eliminate the interference of other ingredients such as lipids in dough on the interaction between gluten and starch in dough processing,the model dough was prepared with gluten and wheat starch according to the proportion of high,medium and low gluten flour according to the national standard.The effects of different Na Cl levels on the properties of high-gluten,medium-gluten and low-gluten model dough during formation,heating and short-term retrogradation were studied,and the related mechanisms were preliminarily clarified from the perspective of the interaction between gluten protein and wheat starch.The main results are as follows:(1)The effects of Na Cl addition on the texture,rheological and thermomechanical properties of model dough with different gluten protein contents were studied.The textural and rheological properties studies showed that with the addition of gluten protein or Na Cl,the hardness,chewiness,stickiness and elasticity of the model dough increased significantly(p <0.05),and the elastic modulus G′ also increased,which together explained the model dough structural stability was enhanced.The study of thermomechanical properties showed that with the increase of gluten protein content,the weakening degree,maximum viscosity index and retrogradation value of the control model dough decreased significantly(p <0.05).With the increase of Na Cl addition,the weakening and retrogradation values of the high,medium and low gluten models dough increased significantly(p <0.05),and the maximum viscosity index decreased significantly(p <0.05).And the addition of Na Cl was 1.0% and 1.5%,the weakening degree and retrogradation value of medium,high and low gluten model dough increased significantly(p <0.05),and the maximum viscosity index decreased significantly(p<0.05),which indicating that the effects of Na Cl or gluten addition on the processing characteristics of the model dough in the heating and retrogradation stages were different.(2)Based on the difference of the thermomechanical properties of the model dough in the heating stage,the effect of Na Cl addition on the properties and interaction of gluten protein and wheat starch in model dough with different gluten protein contents was studied.The content of gluten protein increased in the heating stage,and the content of protein molecular force and ordered structure in the control model dough increased continuously,indicating that the dough weakening degree and maximum viscosity index may be related to the structure of wheat starch and the interaction between protein and starch.The results of XRD showed that gluten protein inhibiting the destruction of starch structure by heating,so the interaction between protein and starch was the main factor for the change of dough weakening degree and maximum viscosity index.The results of infrared spectroscopy showed that the content of hydrogen bonds in the control model doughs increased and the hydrophobic force decreased,indicating that the main factor for the significant decrease in the degree of weakening and the maximum viscosity index was that gluten protein promoted the hydrogen bond between protein and starch.interaction(p <0.05)to mitigate heating damage to dough structure.The content of Na Cl increased in the heating stage,the hydrogen bonds between proteins in the high,medium and low gluten model dough first decreased in the weakening stage and then increased in the gelatinization stage.At the same time,the content of hydrophobic force and ordered structure increased all the time.The XRD results showed that Na Cl inhibited the destruction of starch structure by heating,thus the change of dough weakening degree was related to the change of interaction between protein and starch,and the change of maximum viscosity index in gelatinization stage was related to the increase of interaction between protein molecular chain and wheat starch.The results of infrared spectroscopy showed that the hydrophobic force of the high,medium and low gluten model doughs increased,the hydrogen bond content of the high gluten group showed an increasing trend,the hydrogen bond content of the medium gluten group decreased in the weakening stage and increased in the gelatinization stage,and the hydrogen bond content of the low gluten group decreased in the weakening stage and decreased in the gelatinization stage.The main factor for the significant increase in the weakening degree of the model dough after adding salt was that Na Cl destroyed the hydrogen bond interaction between gluten protein and wheat starch in each group(p <0.05),and the dough structure was further damaged.The main factor for the maximum viscosity index significantly decreased was that Na Cl promoted the hydrogen bond and hydrophobic interaction between gluten protein and wheat starch in the high and medium gluten groups(p <0.05),and promoted the hydrophobic interaction between gluten protein and wheat starch in the low gluten group to inhibit the destruction of dough structure by heating.(3)Based on the difference of the thermomechanical properties of the model dough in the retrogradation stage,the effect of Na Cl addition on the properties and interaction of gluten protein and wheat starch in model dough with different gluten protein content was studied.The results showed that the content of gluten protein increased in the retrogradation stage,the hydrophobic force between proteins in the control model dough decreased,and the content of hydrogen bonds and ordered structures increased.The results of XRD indicated that gluten could destroy the hydrogen bonding force between amylose.Further the results of infrared spectroscopy showed that the content of hydrogen bonds in the dough of the control model increased and the hydrophobic force decreased,indicating that the main factor for the significant reduction of the retrogradation value of the dough of the control model was that the gluten protein destroyed the hydrogen bonding force between the amylose and the hydrophobic interaction between the gluten protein molecular chain and the amylose(p <0.05),which made the system not easy to retrograde.The content of Na Cl increased in the retrogradation stage,and the content of hydrogen bond,hydrophobic interaction and ordered structure in the high,medium and low gluten model doughs increased.The XRD results showed that Na Cl promoted the hydrogen bonding force between the amylose groups.Furthermore,the results of infrared spectroscopy showed that the contents of hydrogen bonds and hydrophobic forces in the high,medium and low gluten model doughs increased,indicating that the main factor for the significant increase in the retrogradation value of the model dough after adding salt was that Na Cl promoted the hydrogen bonds and hydrophobic interactions between gluten protein molecular chains and amylose in the high,medium and low gluten model dough(p <0.05),to rapidly form ordered three-dimensional network structures. |
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