12 Fractionation and rheological properties of glutens from near isogenic lines.

Y. POPINEAU, J. Lefebvre, and G. Deshayes. Institut National de la Recherche Agronomique, Centre de Recherches de Nantes, BP 71326, 44316 Nantes cedex 3, France.

Viscoelasticity of hydrated gluten depends on composition of HMW glutenin subunits, size distribution of glutenin polymers and protein-protein interactions. Glutens extracted from four near-isogenic lines differing in their HMW subunits were analysed. Covalent and non-covalent bonds were examined by submitting the material to heating/cooling cycles, in the presence or in the absence of SH-blocking agent (NEMI). Size distribution of prolamins was determined by sequential extraction and SE-HPLC. Rheological properties was studied by dynamic assay in shear and creep and recovery analysis. Assays carried out at 20 C confirmed that viscoelasticity was determined by large glutenin polymers, influenced by the HMW subunit composition. Difference of functionality linked to subunit structure was highlighted by comparing the behaviours of the 1A/1B null and 1A/1D null lines. In the 20–40 C temperature range, no irreversible changes of the mechanical properties occured. Thermal treatment affected chain mobility, and possibly H bonds, but not the structure of the network. Above 40 C, irreversible rheological changes were observed in the absence of NEMI, but not in its presence. Irreversibility was mainly due to chemical modifications affecting the polymer size distribution. The sensitivity of gluten to temperature depended on subunit composition.