Investigation of Dry-Heated Hard and Soft Wheat Flour

The Amylograph profile of dry-heated (120 degrees C, 120 min) wheat flour showed a drastic change, i.e. an earlier onset time and higher peak viscosity than that of a control. However, no difference in the size of the starch granules was observed between dry-heated and normal starch at every temperature. Wheat flour was fractionated with acetic acid, and the separated prime starch (PS) and tailings M fractions were dry-heated at 120 degrees C for 30, 60, 90, and 120 min, respectively. There was almost no difference in the RVA and DSC profiles between PS and dry-heated PS, and T and dry-heated T fractions, i.e., dry heating of wheat flour did not change the structures of starch that would be related to onset time and peak viscosity in the Amylograph profile. We thus excluded the water solubles (WS) fractions from control and dry-heated wheat flour, but the effect of dry heating on the Amylograph profile was not lost. Next, the gluten (G) fraction was excluded following WS fraction from these wheat flours, and Amylograph tests were performed. The Amylograph profiles in both wheat flours were almost coincidental, which showed that the G fraction in dry-heated wheat flour caused the earlier onset time and higher peak viscosity.