Moisture Sorption Characteristics of Starchy Products: Oat Flour and Rice Flour

Moisture sorption isotherms for oat flour and rice flour were determined at 5, 23, and 45 A degrees C using a gravimetric technique in an a (w) range of 0.08-0.98. The results obtained showed that, for a (w) values lower than around 0.75, in both flours, the sorption capacity decreased with increasing temperature, while the opposite behavior was observed at a (w) greater than this value. It was found that the experimental data in the water activity range considered were better represented by the four-parameter Peleg equation. The monolayer water contents for both materials were determined by the BET and GAB models. The net isosteric heats of sorption were estimated using the Clausius-Clapeyron equation. For both materials, the monolayer water content and the isosteric heat of sorption were found to decrease with increasing temperature and increasing moisture content, respectively.