FUNDAMENTAL AND EMPIRICAL RHEOLOGICAL BEHAVIOR OF WHEAT-FLOUR DOUGHS AND COMPARISON WITH BREAD-MAKING PERFORMANCE

The rheological characteristics of wheat flour doughs from the cultiva rs Obelisk and Katepwa and of biscuit flour doughs, and also of biscui t flour doughs containing glutens isolated from cv. Obelisk and cv. Ka tepwa flour, were compared and discussed in relation to bread making p erformance. Four different rheological methods were employed: two fund amental methods, i.e. dynamic (oscillatory) and uniaxial compression t ests, and two empirical methods, i.e. tests using a Brabender Extensog raph and a Chopin Alveograph. The fundamental methods showed that a do ugh of cv. Katepwa flour had a higher resistance to deformation and wa s more elastic than a dough of cv. Obelisk flour. Doughs of biscuit fl our exhibited an intermediate behaviour, except that loss tangent valu es were close to those of a cv. Obelisk flour dough. Addition of cv. O belisk gluten to biscuit flour hardly affected the rheological behavio ur, whereas addition of cv. Katepwa gluten resulted in a higher resolu tion resistance to deformation and a higher elasticity. Uniaxial compr ession tests clearly showed the strain hardening and strain rate thinn ing characteristics of the flour doughs, which were most pronounced fo r a dough of cv. Katepwa flour. The rheological characteristics of cv. Obelisk and cv. Katepwa flour doughs and of biscuit flour doughs cont aining the glutens corresponded with those of the isolated hydrated gl utens. The information about the rheological behaviour of the flour do ughs obtained by the four methods was complementary and in good agreem ent, despite differences in applied strains, deformation rates and mod es of deformation. The empirical tests showed that the extensibility o f the biscuit flour dough was less compared to that of the other dough s. This study suggests that in order to obtain a high loaf volume and a fine crumb structure, wheat flour dough has to exhibit biaxial strai n hardening and extensibility exceeding a minimum level; it is likely that the resistance to deformation may vary within a certain range. (C ) 1996 Academic Press Limited