Molecular Weight Distribution of Gluten Proteins

Abstract

Gluten confers on flour the ability to produce viscoelastic doughs. The molecular weight distribution (MWD) of gluten proteins is one of the main determinants of physical dough properties. Size-exclusion high performance liquid chromatography (SE-HPLC) is routinely used to evaluate this parameter. A proper, highly efficient solubilization protocol plays a vital role in the determination of MWD. Coupling SE-HPLC with multi-angle laser light scattering (MALLS) has brought the possibility of unravelling new information about these polymers. Therefore, finding a solubilization method to study the polymeric structures of gluten by MALLS was our main objective. We used short term extraction with 50% aqueous acetonitrile added with 0.05% triflouracetic acid. This gave better reproducibility than extractants containing sodium dodecyl sulfate (SDS), with similar efficiency. Using flour extracts from the Australian wheat cvs. Chara and Banks we collected 15 sub-fractions from the first peak of the SE-HPLC chromatograms to determine the molecular weight average (Mw) of the fractions, with and without sonication. Similar Mw was found between sonicated and non-sonicated samples for all fractions except the first one (void volume) where the sonicated sample showed higher values. We also found that the majority of high molecular weight glutenin subunits (HMW-GS) eluted in a much narrower sector of the polymeric peak when compared with previous findings. Based on these findings, a solubilization method combining SE-HPLC/MALLS and RP-HPLC was developed