USE of UNIFAC IN the PREDICTION of WATER ACTIVITY VALUES of AQUEOUS POLYOL SOLUTIONS

The water activity (aw) values of two commonly used aqueous polyoi solutions (xylitol and sorbitol) in the confectionery industry were estimated at 25C by using the UNIFAC (universal functional group activity coefficient) model in the aw range 0.50–0.99. the comparison between the experimental and estimated aw values at the high aw region (aw> 0.96) revealed very good agreement. However, the predicted values by the UNIFAC model did not fit well to the experimental data at aw < 0.96, indicating that the UNIFA C method needed to be modified. the agreement between the experimental and predicted values was considerably improved at aw < 0.96 when the modtfled UNIFAC model was used.