Phase separation of wheat flour dough studied by ultracentrifugation and stress relaxation. I. Influence of water content.

Separation of starch and gluten into two aqueous phases is an important aspect of wheat flour dough development. The fact that starch can easily be washed from dough, leaving behind a gluten gel, illustrates the phase separation of dough very well. To study this phase separation, dough was subjected to high centrifugal forces of 100,000 X g. The tendency of starch and gluten to separate into two phases is reported for six wheat cultivars at water contents ranging from 38 to 50%. At high water contents, a separation of the dough into liquid, gel, gluten, and starch phases was observed. When the water content was reduced, unseparated dough was found at the bottom of the test-tube. At low water contents no separation was observed. The influence of dough water content on the stress-relaxation modulus was considerable at water contents where no separation took place. For doughs prepared with increasing water contents, where separation occurred, the modulus was less affected. This was interpreted as being the region where gluten development was complete. Separation properties varied for cultivars of wheat. Three cultivars with the same relative amounts of separated phases produced roughly the same stress-relaxation modulus.