MEASURING AND MODELING GRAIN SORPTION EQUILIBRIA OF AMARANTH GRAINS

Water activity (a(w)) of Amaranthus cruentus were measured at 35, 45, and 65 degrees C at different moisture contents by means of an electro nic water activity meter. Experimental curves were fitted to one three -parameter equation (GAB equation). The equilibrium values and tempera ture shifts were modeled with a three-parameter equation in the approx imate a(w) range of 0.03-0.88. An analytical expression to calculate t he isosteric heat oi sorption and its moisture content dependence was used, and the results were compared with the isosteric heat calculated from the experimental equilibrium data by means of the Clausius-Clape yron equation.