No abstract

An on-line coupling of HPSEC-MALLS and a RP-HPLC procedure were used to characterize and to 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, the size distribution of protein and the 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 MT was reached, while detectable changes in subunit composition occurred also after the peak MT. Even if sonication, which was used to solubilize the total wheat glutenin, can narrow down the glutenin size distribution, HPSEC-MALLS revealed a close relationship between the SDS solubility of the glutenin polymers and their size distribution confirming a depolymerization and repolymerization hypothesis. During the depolymerization of the SDSunextractable polymers, glutenin subunits were released in nonrandom order, which was indicative of the polymers' having a hierarchical structure. Some HMW-GS (specially HMW-GS 1Dx5) 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 its potential to form branched structure. These studies suggest that the SDSunextractable polymers in flours have a well-ordered structure that can be modified by dough mixing and resting. Cereal ChemistryT. Aussenac et al. 3

BACKGROUND: Optimization of nitrogen (N) and sulfur (S) nutrition of wheat influences the bread-making quality of grain. This study was conducted to determine whether the application of N and S in winter wheat at anthesis stage during two field trials could influence the absorption and distribution of N and S in grain and flour bread-making quality

Nitrogen (N) and sulfur (S) supplies have a strong influence on the quality and quantity of wheat storage proteins, which play an important role in the breadmaking process. Nitrogen derived from urea, S from micronized elemental sulfur, and a mixture of both (N+S) were applied at anthesis stage on wheat by foliar spray. To relate N and S incorporation in storage proteins to the quality of dough, their incorporation into each storage protein fraction was measured: monomers, low molecular weight glutenin subunits (LMW‐GS), and high molecular weight glutenin subunits (HMW‐GS). Then protein fraction quantities, molecular weight distribution (MWD), polymerization index (PI), and molecular dimensions of unextractable polymeric protein (UPP), as well as dough mixing properties were determined. Fertilizers N and S were differentially incorporated into each storage protein fraction, influencing protein synthesis. Moreover, after the N+S fertilization, the increase of the polymeric proteins induced an increase in molecular weight and compactness, as well as in dough strength and consistency. These results provide evidence that N and S fertilizers applied by foliar spray route at anthesis, simultaneously, play an important role in controlling the storage protein synthesis and the degree of polymerization, which in turn influence dough mixing properties.