43 The effect of starch granules on rheological properties of wheat flour dough.

H. Larsson. University of Lund, Dept of Food Technology, Box 124, S-221 00 Lund, Sweden.

The relationship between rheological properties of wheat flour dough and flour quality, i.e. breadmaking quality is complex. During the course of bread making a dough is subjected to different deformation and deformation rates. However, the rheological properties are derived from the dough components and their organisation. Wheat flour dough is a composite material, in which the starch or filler phase can be regarded as continuous or more or less dispersed, depending on the composition of the dough and its development, i.e. mixing. The rheological properties of gluten may be more or less masked by the high starch content (approx. 50%) of dough. This paper presents results where the rheological behaviour of dough in shear deformation could be attributed to an effect of the starch granules. The large surface area provided by the starch granules in dough was demonstrated by modifying the surface of the granules. An effect on the elastic modulus (G’) and the behaviour upon strain at small deformation in shear were established. Also the effect of mixing time on dough made up with various starch contents showed to influence the same rheological parameters. For the discussion of the results the dough is considered as consisting of two continuous aqueous phases, where the hydrated gluten is one. The second phase will be the starch granules organised into a weakly aggregated structure which distributes the remaining water within the dough.