Comparison of protein extraction procedures to assess the effect of quantitative protein composition on the bread-making quality of south african winter wheat cultivars

Abstract

A suitable technique for the extraction of wheat flour protein fractions was pursued to assess the effect of quantitative protein composition on the bread-making quality of winter wheat cultivars on a large scale. Nine procedures involving the use of different sequential solvent extractions were quantitatively compared. The distribution of protein components in the different solubility classes was checked by means of sodium dodecyl sulphate Polyacrylamide gel electrophoresis. The most effective procedure to fractionate the four major protein groups sequentially was: albumin (water),' globulin (0.5 M NaCI + 0.05 mM Na-EDTA), gliadin [55% (v/v) propan-2-ol] and glutenin [0.0125 M Na2B4O7, 0.043 M NaOH, 0.5% (m/v) SDS, 1% (v/v) β-mercaptoethanol].To validate this procedure, linear correlations between quality parameters and protein extracted for all localities and cultivars were complemented by principal component and best subset regression analysis. Albumin and globulin were weakly correlated with quality attributes whereas gliadin and glutenin were highly positively correlated. The contribution of relative glutenin content to dough strength was also confirmed. Since these results complied with present concepts on the relationships between protein fractions and functional properties, it was concluded that the technique could be applied for the protein fractionation of South African winter wheat cultivars. © 1993 Taylor and Francis Group, LLC.