Study On Isolation And Structure Of Wheat Gliadin And Glutenin From Wheat Gluten

Wheat gluten is a high quality and cheap plant protein resources, but its unique amino acid composition has limited its scope of application. In this paper, wheat gluten was used as raw materials, separated and purified wheat gliadin and glutenin, determined the optimum conditions for separation, analysised the basic functional properties of various proteins, and studied the structural properties of the proteins. Then the wheat gliadin was phosphorylation modified with the viscosity index for the evaluation, in order to study the changing nature of the modified protein function.Wheat gluten protein composition was that:crude protein content72.57%, crude fat2.23%, water content9.55%, starch5.67%, ash1.56%, and other8.42%. By single factor and orthogonal experiments, the optimal parameters of separating wheat gliadin and glutenin was determined:gliadin was that,ethanol concentration65%, liquid-solid ratio30:1, extraction time2.5h and temperature35℃; gluten was that:pH10, liquid-solid ratio30:1and extraction time2.5h.In these conditions, the yield of gliadin and gluten was37.21%and27.16%respectively, the protein purity was96.88%and89.47%respectively.Under the condition of room temperature25℃and pH7.0, the solubility of wheat gliadin and glutenin were lower, while the foamability, foaming stability, emulsifying and emulsion stability were better, but the viscosity varies greatly.Using scanning electron microscopy (SEM) to watch the structure of wheat gluten, wheat gliadin and wheat glutenin, the results showed that the SEM of the three proteins have significant differences; the thermal denaturation process of wheat gluten, wheat gliadin and glutenin were studied by DSC analysis, the proteins had two different thermal denaturation peaks with temperature changing, and gliadin had the best heat resistance; amino acid analysis results showed that the amino acid composition of wheat gluten, gliadin and glutenin the amino acid composition were all complete, the ratio was relatively balanced, the wheat gliadin had the highest essential amino acid index, the amino acid score (AAS), chemical score (CS), essential amino acids index (EAAI) of wheat gluten were4.90%,3.61%and81.42%respectively; the AAS, CS, EAAI of gluten were4.82%,3.57%and78.37%respectively; the AAS, CS,and EAAI of gliadin were6.42%,4.74%and 85.62%respectively, three nutrition indicators showed that the nutritional value of wheat gliadin was the best; Fourier transform infrared spectras showed the wheat gliadin and glutenin had the characteristic absorption bands in the FTIR spectra, and the characteristic functional groups were mainly the same.Sodium polyphosphate was used to phosphorylate wheat gliadin with the viscosity index for the evaluation, after single factor experiments and orthogonal experimental, the optimal process was the radio of sodium polyphosphate and wheat gliadin1:2at25℃and pH9.5for l.Oh. At the conditions the degree of phosphorylation of modified gliadin was6.43mol/mol of Pr, FTIR spectra showed modified protein have the P-O-C group and the PO43-group’s characteristic absorption peaks after the introduction of phosphate groups. Compared to the original gliadin, the solubility, emulsibility, emulsion stability and foamability of modified gliadin was improved obviously.