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. T,he 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%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. am die effek van kwantitatiewe prote·iensamestelling op broodbakkwaliteit op groot skaal te ondersoek, is die wenslikheid van verskeie prote·ienekstraksieprosedures nagegaan. Nege prosedures, wat uit verskillende ekstraheermiddelkombinasies bestaan het, is kwantitatief met mekaar vergelyk. Die verspreiding van prote·ienkomponente binne oplosbaarheidsklasse is met behulp van natrium dodesiel sulfaat poliakrielamiedgelelektroforese nagegaan. Die effektiefste prosedure om die vier prominente prote"ien fraksies opeenvolgend te skei, was: albumien (water), globulien (0.5 M NaCI + 0.05 mM Na-EDTA), gliadien [55% (v/v) propan-2-01] en glutenien [0.0125 M Na2B4~' 0.043 M NaOH, 0.5% (m/v) SDS, 1 % (v/v) ~-mercaptoethanol] .Om die toepassing van die tegniek te toets, is die verband tussen kwantitatiewe prote·iensamestelling en kwaliteitseienskappe met liniere korrelasies, hoofkomponent-en beste substel regressie analise oor lokaliteite en cultivars bereken. Albumien en globulien is swak met kwaliteitseienskappe gekorreleer, terwyl gliadien en glutenien hoogs beduidend gekorreleer is. Die bydrae van glutenien-inhoud tot deegsterkte is ook bevestig. Hierdie resultate kom ooreen met bevindinge rakende die verband tussen prote·ienfraksies en funksionele eienskappe. Die tegniek is dus vir die fraksionering van Suid Afrikaanse winterkoringprote"ien geskik.