Effect Of Parameters Of Mixing Flour On Physical And Chemical Properties Of Wheat Protein

Mixing flour after adding water to flour is a key part of the pasta manufacture.Under the action of water,wheat flour forms the gluten network,and other components are filled into the network structure to make the dough viscoelastic,which lays the foundation for the pasta manufacture.Protein aggregates and water molecules attract each other during the gluten formation,which promotes the dissolution of protein aggregates,and transforms proteins from closely packed structures into independent molecules in aqueous solution.The hydrophilic groups on the surface of these molecules increase the degree of freedom due to the presence of water molecules and the increase of the molecular spacing,especially in the single chain of the side chain,which allows the side chain to rotate.And the opportunity for the surface reactive groups of the protein molecule to generate chemical bonds increases.This facilitates the association between molecules and promotes the formation of gluten network.The hydrophobic groups inside these molecules increase the chance of hydrophobic sites exposure due to the unfolding of hydrophilic groups on the surface.The solvation in this process changes the structure of protein aggregates,including the light scattering characteristics in the dough,the content and the light scattering characteristics of protein components.The research uses the semolina of Hebei Jinshahe Noodle Group Co.,Ltd.as the test material,and the farinograph and extruder to mixing semolina are the research process.The mixing time of farinograph(0,4.5,9.0,35.0,55.0min),the barrel moisture(25,35,45%),the barrel temperature(30,40,50°C),the screw speed(100,150,200 rpm),with or without die and the extrusion rounds(1,2,3 rounds)is the test factor and level.Detecting and analyzing the content of sodium dodecyl sulfate(SDS)soluble protein,SDS-insoluble protein(GMP),the diffusion behavior of photon and extruded flour,the weight average molar mass(Mw),z-average radius of gyration(Rgz),polydispersity index,particle size distribution of SDS-soluble protein and sonication-solution protein and other light scattering characteristics and aggregate morphology.Further understand the mechanism of mixing flour by farinograph and extruder,in order to provide the reference for selection of the extrusion mixing process parameters.The main results are as follows:The specific mechanical energy(SME)of dough in different mixing time is 1.9~48.8kJ/kg,and the SME of different extrusion parameters is 30.09~178.14kJ/kg.The SDS-soluble protein content of the dough at different mixing time is 81.7~99.1 mg/g,and the GMP content is18.3~31.0 mg/g.The SDS-soluble protein content of the dough with different extrusion parameters was81.7~100.7 mg/g,and the GMP content was 18.3~31.1 mg/g.As the mixing time and SME increase,SDS-soluble protein content increases and the GMP content decreases.The photon transport mean free path in the dough at different mixing times increases as the consistency of dough increases,and consistency of diffusion decreases after consistency of dough decreases.The photon transport mean free path in the dough with different extrusion parameters decreased with the increase of SME.The Mw of the SDS-soluble protein of the dough at different mixing time was increased to 14.25×10~5 mol/g,and decreased to10.28×10~5 mol/g after 55 min,and the Mw of sonication-soluble protein was about 1.500×10~6 mol/g.The dough with different extrusion parameters increased with SME,and the Mw and Rgz of SDS-soluble protein increased and then descreased.The Mw of sonication-soluble protein fluctuates at2.000~2.500×10~6mol/g,and the Rgz has upward trend.Conclusion:The photon transport mean free path in the dough suggests that the process of mixing flour includes wheat flour hydration,gluten network formation and gluten network structure is broken.The content of SDS soluble protein was linearly positively correlated with SME,and the GMP content was linearly negatively correlated with SME.The effect of extrusion mixing is between the farinograph mixing and the uniaxial shear.The content of SDS soluble protein in the dough gradually increased,the structure became loose from compact and the morphology changed from spherical to branched with the increase of mixing time.Sonication soluble proteins are mainly loose structures with super-branched,loosely connected polymers and hollow spheres.