381 Drying kinetics of gelatinized whole wheat.

M. Turhan and S. GUNASEKARAN. Biological Systems Engineering Department, University of Wisconsin–Madison, Madison, WI 53706.

Drying characteristics of whole wheat gelatinized in water was studied. Wheat samples were cooked in distilled water at 70, 80, and 90 C until maximum gelatinization was attained. The extent of the gelatinization was determined using a differential scanning calorimeter. At 70, 80, 90 C the gelatinization were 64, 82, and 94%, respectively. Drying experiments were conducted in a laboratory two-cell bubble-bed drier. The cylindrical cells made of wire mesh (each 32-mm diameter and 26-mm deep) were stacked one over the other in a long, 34-mm diameter Plexiglas column. The experiments were performed at different air temperatures (25, 50, and 75 C) and at air velocity between 2.5 and 3.5 m/s. Small samples of gelatinized wheat (about 15 g) were used. As the drying progressed, the sample mass and individual kernel dimensions (along three orthogonal axes) were measured periodically. We determined that the drying rate and accordingly drying constant increased with the increasing cooking temperature and drying temperature. Drying primarily took place in the falling rate period. Samples were assumed to be infinite cylinder for modeling of drying kinetics. The effective moisture diffusivity was determined to be between 10(^–10) and 10(^–11) m(^2)/s. The diffusivity increased with the increasing cooking temperature and drying temperature. An Arrhenius-type model was used to express the effect of drying temperature on moisture diffusivity.