Rheological behaviour of wheat glutens at small and large deformations. Effect of gluten composition

Glutens derived from two wheal cultivars with a known difference in bread making quality, i.e. cv. Katepwa (good) and cv. Obelisk (poor), were fractionated into gliadin and glutenin. Cultivar Katepwa gluten contained more glutenin than cv. Obelisk gluten. Reconstituted glutens were prepared by mixing, in different ratios, gliadin and glutenin fractions that originated from one gluten type or from both glutens. The rheological properties of these mixtures, when hydrated, were studied at small deformations in shear and at large deformations in biaxial extension. The reconstitution of gluten in its original glutenin/gliadin ratio produced a composite that had a somewhat higher resistance to deformation and was more elastic than the unfractionated gluten. This was true for both gluten types. However, the difference between the theological behaviour of both reconstituted gluten types was comparable with that found between the native glutens. From measurements with glutens reconstituted at various glutenin/gliadin ratios, it appeared that the main factor determining the theological behaviour of hydrated gluten is the glutenin/gliadin ratio. By interchanging thee gliadin and glutenin fractions of the two glutens, it was shown that the source from which the fractions originated, particularly that of the glutenin fraction, was also important. (C) 1996 Academic Press Limited