摘要：Desorption isotherms of hydrated corn starch and their gels containing sucrose or sodium chloride were determined by using the static gravimetric method. Experiments were carried out at 25°C over a water activity range of 0,11-0,75. BET, GAB, Hatsey, Henderson, modified BET, Oswin and Smith equations were tested to fit the experimental moisture sorption data. None of the equations were found to be satisfactory to represent the desorptional data for all samples over this aw range. The GAB and the modified BET equations fitted the data for hydrated and gelatinized starches with or without sucrose in the aw range of 0,11 -0,75. Component interactions in the sucrose-starch-water and sodium chloride-starch-water systems were investigated. Sucrose-starch or sodium chloride-starch interaction was determined by measuring the reductions in water desorption as compared to theoretical. The desorptional behaviors of each component in the hydrated starches depended on the aw and no interaction was detected between starch and sucrose or starch and sodium chloride. In the gel matrix, however, equilibrium moisture contents decreased due to the polymer-soluble interaction. Net isosteric heats of moisture desorption were estimated from equilibrium sorption data, using the integrated form of the Clasius-Clapeyron equation.
