FRACTIONATION OF WHEAT-FLOUR PROTEINS BY SIZE EXCLUSION-HPLC ON AN AGAROSE-BASED MATRIX

Protein, extracted by sonication from flours of Australian wheat cultivars, was fractionated into three resolved peaks by SE—HPLC on an agarose-based matrix (Superose-12). The addition of NaCl (0·08 m) to the buffer system [0·05 m Na phosphate, pH 6·9, containing 0·1 % (w/v) SDS] improved resolution compared with published results on silica-based (TSK series) matrices. The efficiency of protein extraction by microsonication was evaluated by direct assay of the amount of protein in the residue and supernatant using the same method (Dumas). It was found that the unextracted proteins comprised 2–5 % of the protein content of flours derived from five cultivars. Protein in the residue of flour after sonication was also quantified by the areas of SE—HPLC profiles and found to be less than 1·5 % of the total flour proteins. Partial characterization of the proteins under these peaks was achieved by a sequential NaCl extraction in conjunction with SE—HPLC and SDS—PAGE analysis. It was confirmed that peak 1 and peak 2 comprised predominantly glutenin and gliadin, respectively. The third peak contained albumins/globulins and some glutenin components similar to those in the first peak. © 1992, Academic Press Limited. All rights reserved.