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Changes in SDS Solubility of Glutenin Polymers During Dough Mixing and Resting¹

¹Research supported by a grant from Conseil Régional Midi-Pyrénées, Contract RECH 9507769. This work is based on a poster presented at the AACC Annual Meeting, October 1999, Seattle, WA. ²Department of Plant Physiology, E.S.A. Purpan, 75 voie du TOEC, 31076 Toulouse cedex 03 France. ³Corresponding author. E-mail: aussenac@esa-purpan.fr

An online coupling of high-performance size-exclusion chromatography (HPSEC) combined with multiangle laser-light scattering (MALLS) and a reverse-phase HPLC procedure were used to characterize and reveal the polydispersity of the glutenin polymers of doughs during mixing and resting. Experiments involved doughs prepared from several samples of a common French wheat cultivar (Soissons) differing in total amount of SDS-unextractable glutenin polymers. During dough mixing, the amounts, size distribution of protein, and glutenin subunit composition within the SDS-unextractable polymers changed. However, the major changes in SDS-unextractable glutenin content and size distribution occurred before the peak mixing time (MT) was reached, whereas detectable changes in subunit composition also occurred after the peak MT. Even if sonication, which was used to solubilize the total wheat glutenin, can narrow the glutenin size distribution, HPSEC-MALLS revealed a close relationship between the SDS solubility of the glutenin polymers and size distribution, confirming a depolymerization and repolymerization hypothesis. During the depolymerization of the SDS-unextractable polymers, glutenin subunits were released in nonrandom order, which indicated that the polymers have a hierarchical structure. Some HMW glutenin subunits (HMW-GS), especially 1D×5, were particularly resistant to the depolymerization mechanism. This suggested that the subunit plays a major role in forming the backbone of the SDS-unextractable polymers, consistent with the potential to form branched structure. These studies suggest that the SDS-unextrac-table polymers in flours have a well-ordered structure that can be modified by dough mixing and resting.