The dynamic rheological properties of glutens and gluten sub-fractions from wheats of good and poor bread making quality

The dynamic rheological properties of glutens and gluten fractions (gliadin and glutenin) of two U.K.-grown wheat cultivars, Hereward and Riband, having good and poor bread quality, respectively, were studied. Gluten and glutenin doughs from cv. Hereward had higher G' and lower tan δ values than those from cv. Riband at all frequencies studied. A more pronounced difference in G' and tan δ was observed between the glutenin doughs of the two wheats than between their respective gluten doughs. The rheological properties, i.e. G' and tan δ values, of gliadin doughs were similar for both wheats. Varying the gliadin/glutenin ratio by adding the isolated gliadin or glutenin sub-fractions to the parent glutens showed that the G' values decreased and the tan δ values increased as the gliadin/glutenin ratio was increased for both cultivars, indicating a considerable decrease in elasticity as the gliadin/glutenin ratio increased. The decrease in G' may be attributed to a plasticising effect of gliadin and ‘interference’ of gliadin with glutenin-glutenin interactions. The reduction in G' was much more pronounced when the gliadin/glutenin ratio was increased between 0.15 and 1.0 than between 1.0 and above. Gluten from cv. Hereward had higher G' and lower tan δ values than cv. Riband gluten at all gliadin/glutenin ratios, indicating that cv. Hereward gluten had greater elastic character than cv. Riband gluten. Although significant effects of other non-protein hydrocolloid components cannot be discounted, these observations are consistent with the view that the viscoelasticity of the glutenin sub-fraction of gluten and differences in the ratio of gliadin to glutenin are the main factors governing inter-cultivar differences in the viscoelasticity of wheat gluten.