RHEOLOGICAL BEHAVIOR OF WHEAT GLUTENS AT SMALL AND LARGE DEFORMATIONS- EFFECT OF GLUTEN COMPOSITION

Glutens derived from two wheal cultivars with a known difference in br ead making quality, i.e. cv. Katepwa (good) and cv. Obelisk (poor), we re fractionated into gliadin and glutenin. Cultivar Katepwa gluten con tained more glutenin than cv. Obelisk gluten. Reconstituted glutens we re prepared by mixing, in different ratios, gliadin and glutenin fract ions that originated from one gluten type or from both glutens. The rh eological properties of these mixtures, when hydrated, were studied at small deformations in shear and at large deformations in biaxial exte nsion. The reconstitution of gluten in its original glutenin/gliadin r atio produced a composite that had a somewhat higher resistance to def ormation and was more elastic than the unfractionated gluten. This was true for both gluten types. However, the difference between the theol ogical behaviour of both reconstituted gluten types was comparable wit h that found between the native glutens. From measurements with gluten s reconstituted at various glutenin/gliadin ratios, it appeared that t he main factor determining the theological behaviour of hydrated glute n is the glutenin/gliadin ratio. By interchanging thee gliadin and glu tenin fractions of the two glutens, it was shown that the source from which the fractions originated, particularly that of the glutenin frac tion, was also important. (C) 1996 Academic Press Limited