78 Effect of shear rate on the viscoamylographic profile of rice flours and starches.

Charles F. Shoemaker. University of California, Riverside.

A study of the effect of shear rate on the amylographic profiles of rice flours and starches was conducted. In order to provide a controlled shear rate, a cone and plate rheometer was used to measure the viscoamylographic profiles. Rice flours with different amylose contents were analyzed. The temperature program used consisted of four segments: 1) 45 to 95 C in 3.5 min., 2) holding. at 95 C for 2.3 min, 3) 95 to 50 C in 3.5 min., and 4) holding at 50 C for 1.25 min. A significant effect of shear rate on the shape of the amylographic profile of the rice flours was observed. The use of a shear rate of 200 s(^–1) was found to provide for a better resolution of the amylographs of the different rice flours than that at 400 s(^–1).