Kinetics of Water Absorption in Rice

Water absorption rate of three different rice, i.e. low, medium and high amylose content rice, were evaluated based on their kinetic reactions. Water absorption kinetics were determined at below (28, 50, 60 and 70 degrees C) and above (80, 90 and 100 degrees C) gelatinization temperatures. Reaction rate constant was evaluated from the curve of relation between moisture content and soaking time, and activation energy was calculated with Arrhenius equation. The results showed that water absorption at below gelatinization temperature followed first order reaction, while at above gelatinization temperature reaction followed with zero order. Rice with high amylose content tended to absorb water easier than low amylose one at temperature less than 70 degrees C, however, it was vice versa at temperature above 70 degrees C. Activation energy of water absorption below the gelatinization temperature was lower than above gelatinization temperature.