2012 Volume 18 Issue 5 Pages 617-622
The moisture sorption isotherms of durum semolina were observed in the temperature range of 30 to 80°C for both the sorption and desorption processes. The isotherms of its constituent starch and gluten were observed at 30°C and that of spaghetti was observed at 60°C. All the isotherms were well expressed by the Guggenheim-Anderson-de Boer equation. The isotherm for the desorption process lay over that for the sorption one at any temperature, and a slight hysteresis was recognized. Isosteric heats, q, for sorption and desorption processes were estimated according to the Clausius-Clapeyron equation as a function of the moisture content of durum semolina. The q values were larger at lower moisture contents, indicating that water molecules more strongly interact with the wheat flour at lower moisture contents. The q values for the desorption process were greater than those for sorption. The isotherms of starch lay over those of gluten at any water activity, and those of spaghetti were located between those of starch and gluten.
