Effect Of Different Batter Treatments On The Separation Effect And Characteristics Of Wheat Starch And Gluten Protein

Starch and gluten protein are the main components of wheat flour,and both are now widely used in the food,chemical,feed and medical industries,with demand increasing yearly.The production of gluten meal(gluten protein)and wheat starch in China still needs to mature,and the conversion rate of wheat to deep processing is low.As a standard separation method in the modern wheat wet separation industry,there is still much scope for optimizing the separation process.This thesis investigated the effects of homogenization,salt,aqueous ozone and pH treatments on the separation of gluten protein and starch from the slurry method,as well as the functional and structural properties of the product.Objective To clarify the relationship between the aggregation behaviour of gluten protein and the separation effect of starch and gluten,to find a stable and reliable starch and gluten processing process,and to provide a reference for controlling the separation of starch and gluten in practical industry and improving the processing suitability of wheat flour.Firstly,the effect of salt and homogenization speed on the separation effect of starch and gluten protein was studied.The results show that the weak concentration of salt helps to reduce the hydrophobicity of the protein surface and expose the polar residues,leading to increased gluten hydration;the shear force generated by homogenization breaks the slurry into smaller particles,and gluten and starch particles are free from each other,gluten particles are in complete contact with water molecules and absorb water;gluten protein aggregation absorbs water to increase the density difference between them and starch particles,which helps the centrifugal separation of the two phases,significantly(p < 0.05)increased the yield of A-starch.Reducing the slurry’s viscosity helped reduce spatial site resistance during gluten protein aggregation,which reduced the mobility of the components in the slurry and gluten agglomeration,facilitating the separation of starch and gluten protein.Salt addition and increased homogenization rate induced oxidation of gluten free sulfhydryl groups(SH)to form inter-or intra-chain disulphide bonds,which promoted the formation of glutenin macromers(GMP);the microstructure was characterized by a thick,laminar gluten matrix,and macroscopic expression was enhanced by water absorption,hardness,and tensile strength.However,with increased gluten protein hydration,the secondary structure shifts to a β-turn,with macroscopic manifestations of reduced viscoelasticity and increased ductility.Salt inhibited starch gelation through electrostatic interactions;the shearing effect of homogenization led to a significant increase in the content of broken starch,which was not conducive to starch recrystallization and increased starch resistance to aging.Next,the effect of aqueous ozone on the separation effect of starch and gluten protein was investigated.The results showed that the recovery of starch separated from the slurry formed by aqueous ozone pretreatment increased by 4.7% compared to the conventional process,and the purity of gluten protein and starch was significantly improved(p < 0.05).Aqueous ozone significantly reduced the total number of bacteria in the product and extended the shelf life of the product.After ozone treatment,the starch pasting temperature decreased significantly(p < 0.05),indicating that aqueous ozone treatment could disrupt the starch’s molecular structure and make it easier to paste.The decrease in starch crystallinity,the deconvolution of branched starch and the increase in the content of broken starch lead to an increase in starch aging resistance.Ozone oxidizes free sulfhydryl groups to form disulphide bonds,leading to the polymerization of glutenin macromers.At the same time,the disulfide bond conformation shifted to gauche-gauche-gauche(g-g-g),and the secondary structure shifted to β-Sheet,resulting in a more stable and ordered glutenin network structure,which macroscopically exhibited enhanced water solubility,water retention,viscoelasticity and tensile resistance.SEM observed that the pores of the glutenin network structure became larger after a high concentration of aqueous ozone treatment,with fractures in several regions.Microstructural changes suggest that high ozone concentrations can damage the gluten structure by excessive oxidation.Finally,the effect of pH on the separation of starch and gluten proteins was investigated.The results showed that separating starch and gluten protein under neutral conditions resulted in higher yields and purity.Starch separated under acidic or alkaline conditions tended to dissolve and break and had low crystallinity and poor thermal stability during pasting.Gluten proteins isolated under neutral and alkaline conditions have better functional properties such as water solubility,water retention and viscoelasticity;acidic conditions are not conducive to maintaining gluten protein elasticity.The results showed that pH affected the amino acid residue microenvironment of gluten proteins.The tyrosine and tryptophan residues of gluten proteins isolated under neutral and alkaline conditions tended to be buried,which was beneficial for protein folding and aggregation.pH 7 showed that the β-sheet and disulfide bond g-g-g conformations of gluten proteins isolated under neutral and alkaline conditions were considered,and the spatial structure was more stable and orderly.SEM observed a decrease in the number of glutenin pores and increased network density under alkaline conditions.Alkalinity promoted the formation of gluten macroaggregates,and the gluten network was strengthened,which was positively correlated with the disulphide bond g-g-g conformation,indicating that wheat gluten contributed more to the strength of the gluten network.In summary,highly aggregated gluten proteins can increase the density difference with starch through water absorption and swelling,making the two phases more easily separated in the centrifugal field.The different treatments indirectly affect the efficiency of the separation process and the product’s end use by changing the behaviour of gluten protein aggregation.The research in this paper is instructive for practical industrial control of starch-gluten separation and improved processing suitability of wheat flour.