Gluten and the starch-gluten interface in relation to the viscoelastic properties of durum dough

Processing properties and behaviour of dough under various processing conditions may be predicted through an understanding of dough fundamental rheological properties. A series of studies were conducted, initially to develop small-scale methods that would discriminate between samples varying in dough strength, followed by enrichment studies to assess the contributions of gluten and its fractionated components, and lastly to examine the role of the gluten-starch granule interface in dough viscoelastic behaviour. Dynamic and creep compliance measurements were made in the linear viscoelastic regime, where response was independent of applied stress or strain. An experimental protocol for large deformation creep measurements was found to predict dough extensibility well.; Effects of dough moisture content, protein content and wheat growing environment on dynamic and shear extensibility measurements were assessed. Dough moisture content was shown to affect both tests. However, dough samples always ranked in the same order at a given water absorption level. Subsequent testing of doughs was conducted at fixed absorption. Protein content did not have a significant effect (p > 0.05) on storage modulus (G′), but did strongly affect tan δ (G″/G′ ). Tan δ and shear extensibility both increased with increasing protein content.; In addition to samples varying in protein content, a series of durum cultivars ranging in intrinsic dough strength was analyzed. Dynamic measurements proved capable of discriminating between durum samples ranging in dough strength. Mechanical properties were strongly correlated with many of the alveograph and micro-mixograph parameters. Tan δ was again strongly influenced by protein content.; Recognizing that protein content affected dynamic measurements, creep compliance tests were conducted using a series of common wheat and durum wheat dough samples with a relatively narrow range in protein content. A creep time of 10,000 s was sufficient to reach steady state flow for all doughs. Creep compliance curves were modeled using a six parameter Burgers model, and interpreted in the context of physical gels with reversible crosslinks and entanglements. The entire elastic compliance curve shifted to lower values and steady state viscosity increased as the strength of durum dough (as measured by extensigraph) increased. The elastic compliance curves for common wheat doughs were steeper and the steady state viscosities were lower than for durum doughs of comparable strength. (Abstract shortened by UMI.)...