Viscoelastic properties of durum wheat and common wheat dough of differentstrengths

Linear viscoelastic properties (LVP) were determined for five durum wheat d oughs and five common wheat doughs (representing four different classes of Canadian common wheat) of different strength using creep testing. A creep t ime of 10,000 s was sufficient to reach a state of steady state flow for al l of the doughs. Creep compliances were analyzed in terms of a Burgers mode l. For the durum doughs, the entire elastic compliance curve was shifted to higher values as the strength of the dough (as measured by extensigraph) d ecreased, while the steady state viscosity increased with strength. For com mon wheat doughs, the elastic compliance curves were steeper and the steady state viscosities were lower than for durum doughs of comparable extensigr aph strength. The retardation strengths associated with a maximum in the re tardation spectra were lower for the stronger durum doughs than for common wheat doughs of comparable strength. Differences in the LVP between durum a nd common wheat doughs of similar extensigraph strength were interpreted in the context of physical gels with crosslinks and entanglements, whose cont ributions to material properties are difficult to distinguish in short-time creep or dynamic measurements. The increased extensibility of common wheat doughs relative to durum doughs of comparable extensigraph strength was at tributed to a higher molecular weight fraction in the polypeptide chains, s imilar in some respects to end-linked bimodal polymer networks, The idea of considering these doughs as physical gels was supported by their stress re laxation behavior.