Stress-relaxation properties of mixograph semolina-water doughs from durum wheat cultivars of variable strength in relation to mixing characteristics, bread- and pasta-making performance

Stress-relaxation behaviours of Mixograph semolina-water doughs prepared from Canadian durum wheat cultivars with diverse gluten strength were investigated and related to mixing characteristics, large deformation properties, and bread- and pasta-making quality. Semolina from 'strong' (S) and 'moderately strong' (MS) durum wheat cultivars required a longer Mixograph mixing time (4-5 min) and higher work input (140-196 Arbitrary Units) to mix to peak dough resistance (PDR) than 'weak' (W) and 'very weak' (VW) durum cultivars (2-3 min and 80-117 AU). Extensigraph maximum resistance to extension (Rmax/E ratio) and Alveograph P/L (tenacity to length ratio) values were higher for doughs from S cultivars than for MS, W, and VW cultivars. Doughs from S cultivars exhibited higher storage modulus (G') and lower tan delta values at all frequencies, and slower rates of stress relaxation as compared to MS, W, and VW cultivars. Stress relaxation (times to relax 50% (t50) and 75% (t75) of initial stress) indicated that stronger doughs, which had higher proportions of glutenins, took longer to reach these iso-relaxation states, regardless of their initial relaxation modulus value. The parameters t50 and t75 were also strongly correlated with dough mixing properties, Extensigraph Rmax/E, Alveograph P/L, mixing energy, mixing time and loaf volume obtained by a long and a short bread-making process. However, for S cultivars loaf volume was 10 to 20% lower than that expected of bread wheat of comparable protein content. Stress relaxation data demonstrated no simple correlation to pasta cooking quality indicating that stronger gluten did not translate into a superior pasta cooking quality. Results are interpreted in the context of multimodal networks and transient networks with reversible crosslinks.